No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Determination of free fatty acids in pharmaceutical lipids by 1H NMR and comparison with the classical acid value
Abstract
Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. (1)H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new (1)H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this (1)H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The (1)H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed.
... However, some of these methods still have weaknesses because they require chemical modification of the sample for analysis, as described by Guillen et al. (2003). However, some qNMR methods have recently been reported for the characterization and quality assessment of lipids and oils (Guillén and Ruiz 2003a, b;Skiera et al. 2014;Hafer et al. 2020). ...
... The acquisition was carried out under the conditions mentioned above. Based on the calculation formula of quantitative NMR discussed by Holzgrabe (2010) and Bharti and Roy (2012) and the development by Skiera et al. (2014), furthermore, the results are calculated according to the equation below: ...
... where m s denotes the sample weight in mg, P denotes the purity, M is the molecular weight in g/mol, N s is the number of protons, and I is the 1 H NMR integral area according to Skiera et al. (2014). ...
Red fruit oil (RFO) can be extracted from fruits of Pandanus conoideus, Lam., an endogenous plant of Papua, Indonesia. It is a commonly used essential original traditional medicine. By applying a newly developed quantitative ¹ H NMR (qNMR) spectroscopy method for quality assessment, a simultaneous determination of the saponification value (SV), acid value (AV), ester value (EV), and iodine value (IV) in RFO was possible. Dimethyl sulfone (DMSO 2 ) was used as an internal standard. Optimization of NMR parameters, such as NMR pulse sequence, relaxation delay time, and receiver gain, finally established the ¹ H NMR-based quantification approach. Diagnostic signals of the internal standard at δ = 2.98 ppm, SV at δ = 2.37–2.20 ppm, AV at δ = 2.27–2.20 ppm, EV at δ = 2.37–2.27 ppm, and IV at δ = 5.37–5.27 ppm, respectively, were used for quantitative analysis. The method was validated concerning linearity ( R ² = 0.999), precision (less than 0.83%), and repeatability in the range 99.17–101.17%. Furthermore, this method was successfully applied to crude RFO, crude RFO with palmitic and oleic acid addition, and nine commercial products. The qNMR results for the respective fat values are in accordance with the results of standard methods, as can be seen from the F - and t -test (< 1.65 and < 1.66, respectively). The fundamental advantages of qNMR, such as its rapidity and simplicity, make it a feasible and existing alternative to titration for the quality control of RFO.
... Deterioration processes in lipids are additional sources of FFA. For instance, short-chain FFA can arise from the secondary oxidation of unsaturated aldehydes as well as from the cleavage of lipid hydroperoxides [1,2]. The FFA concentration in vegetable oils depends on multiple factors, namely the quality and variety of raw material, collecting conditions, processing, storage, the age of the oil and deterioration status [3,4]. ...
... At an industrial level, FFA are usually removed from crude oil through a refining procedure, but the process is not 100% efficient. Hence, the quantitative determination of the AV plays a central role as a quality index in production, trading storage, and marketing of edible oils, and in official food and pharmaceutical control [1,3,11]. Both the European Pharmacopoeia and the Codex Alimentarius establish maximum values for AV in pharmaceutical products and edible oils. ...
... Thanks to its favourable properties (spin number I = 1/2, high gyromagnetic ratio equal to 26.75 × 10 7 rad T −1 s −1 and natural abundance of 99.99%), the 1 H nucleus is the most sensitive NMR probe and is suitable for the identification and quantification of even minor components within a short experimental time [2]. 1 H NMR spectroscopy has been widely used to obtain insights into lipid classes, fatty acid composition, levels of unsaturation, and several minor compounds [2,41,42]. Vegetable oils are mainly made up of mixtures of triglycerides, with different substitution patterns according to the length, degree and type of unsaturation of the acyl chains, and by minor components including mono-and di-glycerides, fatty acids, sterols, vitamins, and others [43]. ...
The identification and quantification of free fatty acids (FFA) in edible and non-edible vegetable oils, including waste cooking oils, is a crucial index to assess their quality and drives their use in different application fields. NMR spectroscopy represents an alternative tool to conventional methods for the determination of FFA content, providing us with interesting advantages. Here the approaches reported in the literature based on 1 H, 13 C and 31 P NMR are illustrated and compared, highlighting the pros and cons of the suggested strategies.
... In general, FFA levels between ∼3% and ∼20% relative to oil weight are common in previous studies using hexane as the solvent (Al-Hamamre et al., 2012;Efthymiopoulos et al., 2017;Go et al., 2016;Haile, 2014;Kwon et al., 2013;Vardon et al., 2013), however values as low as 0.31% w/w (Deligiannis et al., 2011) and as high as 59% w/w (Caetano et al., 2012) have been reported, suggesting a significant variation in the composition of oil extracted from different sources with different extraction parameters. The composition of the extracted oil is an important parameter for its subsequent utilization either as a biodiesel feedstock or in the food and cosmetic industry and a number of authors have reported the use of 1 H NMR spectroscopy for the analysis of the composition of lipids and fats containing complex lipid mixtures (Guillén and Ruiz, 2001;Nieva-Echevarría et al., 2014;Satyarthi et al., 2009;Skiera et al., 2014), while it has also been used for the broad analysis of oils extracted from coffee grounds and SCGs (D'Amelio et al., 2013;Jenkins et al., 2014). ...
... The COOH peak could provide a unique signal in the 1 H spectrum for FFAs, however, fast proton exchange processes with water in CDCl 3 result in the broadening of the signal arising from the carboxylic acid group (COOH) at around 12 ppm, such that is not apparent in the spectrum. Skiera et al. (2014) investigated the FFA content in pharmaceutical lipids using NMR spectroscopy. Their method involved the addition of small amounts of deuterated dimethyl sulfoxide (DMSO-d6) to the fatty oils in CDCl 3 , which slowed the proton transfer sufficiently to allow the detection of the COOH signal. ...
... Due to the complex composition of the oils analyzed in this work (including mono-, di and triglycerides), previously reported methods (e.g. (Satyarthi et al., 2009;Skiera et al., 2014Skiera et al., , 2012) needed to be adapted to take account of each of these components. Part of the method used in this paper relied on making an assumption of the average molecular masses of each component. ...
Spent coffee grounds (SCG) are a potentially sustainable source of C16-C18 triglycerides. This study investigates known solvent extraction technologies with a wide range of solvents for lipid extraction from SCGs, and determines the effect of solvent selection and process temperature on the extraction efficiency and composition of the obtained oil. A correlation between increasing solvent boiling point, and therefore process temperature, and improved oil extraction efficiency was observed in Soxhlet extractions with a wide range of solvents. Experiments at elevated temperatures (up to 200 °C) were performed through Accelerated Solvent Extraction (ASE) and temperature increase initially improved the oil extraction efficiency when non-polar solvents were used, before decreasing it at higher temperatures. Utilization of ethanol resulted in the highest oil extraction ratio by ASE (at 165 °C), suggesting that temperature increase is more beneficial to the extraction efficiency of polar solvents. In addition, analysis of the oils was carried out to evaluate the composition of the oils extracted from SCGs using different solvents and extraction parameters. The Nuclear Magnetic Resonance (NMR) results were in agreement with the values obtained from the titrimetric determination of the free fatty acid content (FFA) of the oils in terms of the comparative trends, and also tentatively suggest that some differences in the composition of the extracted oils might be related to the type of extraction solvent used.
... In crude soybean oil, the main substrates for lipid oxidation are triacylglycerols (TAGs) and free fatty acids (FFAs), which make up 95-97% and 0.3-0.7% of oil, respectively 10,11 . Both TAGs and FFAs have been shown to oxidize during thermal treatment of oil 8,[12][13][14] . As shown in Fig. 1, there are two plausible pathways through which these substrates produce oxylipins in heated oil-(1) TAGs can undergo non-enzymatic hydrolysis to produce FFAs, which can oxidize to form free oxylipins (Pathway 1 in blue), or (2) fatty acids within a TAG molecule (i.e. ...
... Hence, more % FFA in a sample reflects more TAG hydrolysis into FFAs, and greater potential for the released FFAs to form primary oxidation products (i.e., oxylipins) and secondary volatiles. However, in oil, fatty acid hydroperoxides (a type of oxylipin) were detected in both TAGs and FFAs 8,[12][13][14] , suggesting that oxidation can occur directly on TAGs, or on FFAs following their release from TAGs. The preferential substrate for lipid oxidation remains unknown. ...
In oil, free fatty acids (FFAs) are thought to be the preferred substrate for lipid oxidation although triacylglycerols (TAGs) are the predominant lipid class. We determined the preferential oxidation substrate (TAGs versus FFAs) in soybean oil heated at 100 °C for 24 h, after validating a method for quantifying esterified and free lipid oxidation products (i.e., oxylipins) with mass-spectrometry. Reaction velocities and turnover (velocity per unit substrate) of FFA, and free and TAG-bound (esterified) oxylipins were determined. FFA hydrolysis rate and turnover were orders of magnitude greater (16-4217 fold) than that of esterified and free oxylipin formation. The velocity and turnover of TAG-bound oxylipins was significantly greater than free oxylipins by 282- and 3-fold, respectively. The results suggest that during heating, TAGs are preferentially oxidized over FFAs, despite the rapid hydrolysis and availability of individual FFAs as substrates for oxidation. TAG-bound oxylipins may serve as better markers of lipid oxidation.
... Acid value determines the acidic or basic constituents in petroleum products and lubricants, and for biodiesels, the acid value is an indicator of the quality of the product (Skiera et al., 2014). Specifically, it detects the presence of any unreacted fatty acids still in the fuel, or of any acids that were used in the processing. ...
... This is also an indication of the condition of the stability of the fuel, because the acid value increases as the fuel ages (Bello and Otu, 2012). For biodiesel blends, the acid number will change as a result of the normal oxidation process over time (Skiera et al., 2014). Once purchased, biodiesel fuel blends that will not be utilized immediately should be monitored for changes in acid number as an indicator of fuel degradation (Bello and Otu, 2012). ...
Biodiesel (GA1) was produced by the transesterification reaction of palm kernel oil (PKO) and methanol catalysed by crushed cashew nut shaft. Biodiesel samples GA2 – GA4 were also produced from the palm kernel oil using conventional base catalysis by NaOH and crushed cashew nut shaft combined with NaOH. The physico-chemical properties and spectroscopic data of the four samples were found to be similar and compared favourably to those of standard biodiesel. Keywords: Transesterification, palm kernel oil, cashew nut shell, methanolysis, biodiesel.
... Data obtained by the two methods were in good agreement. Furthermore, the effects of solvent and oil matrix on line broadening and the chemical shift of the carboxyl group signal were discussed [6]. ...
... The main information given by NMR spectroscopy is chemical shift and intensity of the signals. NMR is commonly used in qualitative and quantitative analysis of natural compounds and plant extracts as well as of edible oils [6]. 1 H NMR was applied for determination of free fatty acids [18]. ...
Since Cannabis species include psychoactive varieties containing high levels of Δ9-tetrahydrocannabinol (THC), psychotropic properties could be wrongly attributed to hemp-seed oil obtained from Cannabis sativa. Hemp oil does not exert any psychotic effect; on the contrary, it may provide significant health benefits, because it has an optimum proportion of ω-6 to ω-3 fatty acids (3:1). Six samples of cold pressed hemp-seed oils were studied by nuclear magnetic resonance (NMR) and Fourier-transformed infrared spectroscopy (FT-IR). These methods were applied to evaluate the ratio of ω-6 to ω-3 fatty acids, to control the origin, composition and presence of adulteration in hemp oils. FT-IR method allowed us to distinguish three oils with the highest level of γ-linolenic acid. Additionally, NMR spectroscopy was applied to determine the ω-6 to ω-3 ratio. The outcomes of the NMR experiment are in agreement with GC outcomes measures. The results indicate that NMR and FT-IR may be used in routine evaluation of hemp-seed oil quality as a fast and reliable method of verification of ω-6 to ω-3 ratio and origin of the oil.
... Free fatty acids (FFAs) in oils, waxes and various pharmaceutical excipients [129] arise from several processes including: (i) the hydrolysis of triacylglycerides (TAGs) during production and storage of the oil, (ii) handling of the row material and (iii) secondary oxidation of unsaturated aldehydes or other oxidation products originating from the cleavage of lipid hydroperoxides resulting in the formation of short chain FFAs [130]. ...
... The method is not sufficiently sensitive to detect small content of FFA in lipids due to the presence of a strong signal from the α-CH 2 protons of esterified groups. Recently, Skiera et al. [129,132] utilized the integration of the free carboxylic group which is extremely deshielded. The method was applied to 305 oil and fat samples. ...
Mono- and polyunsaturated lipids are widely distributed in Nature, and are structurally and functionally a diverse class of molecules with a variety of physicochemical, biological, medicinal and nutritional properties. High resolution NMR spectroscopic techniques including¹H¹³C- and³¹P-NMR have been successfully employed as a structural and analytical tool for unsaturated lipids. The objective of this review article is to provide: (i) an overview of the critical¹H-¹³C- and³¹P-NMR parameters for structural and analytical investigations; (ii) an overview of various 1D and 2D NMR techniques that have been used for resonance assignments; (iii) selected analytical and structural studies with emphasis in the identification of major and minor unsaturated fatty acids in complex lipid extracts without the need for the isolation of the individual components; (iv) selected investigations of oxidation products of lipids; (v) applications in the emerging field of lipidomics; (vi) studies of protein-lipid interactions at a molecular level; (vii) practical considerations and (viii) an overview of future developments in the field. 2017 by the authors.
... Skiera et al. briefly reported a rapid method for the determination of the SV from NMR data based on the integral of the CH 2 protons adjacent to the ester groups (δ H 2.2-2.4 ppm) and on the integral of the 1,2,4,5-tetrachloro-3-nitrobenzene (TCNB) signal at δ H 7.7 ppm, used as an internal standard for quantitative NMR experiments. Five samples (with a single measurement per sample) were tested with the new method; the NMR results were in agreement with the values obtained through the ISO method, consequently pointing at the suitability of the NMR spectroscopy for the determination of the quality indices of fats and oils [14]. ...
The saponification value of fats and oils is one of the most common quality indices, reflecting the mean molecular weight of the constituting triacylglycerols. Proton nuclear magnetic resonance (1H-NMR) spectra of fats and oils display specific resonances for the protons from the structural patterns of the triacylglycerols (i.e., the glycerol backbone), methylene (-CH2-) groups, double bonds (-CH=CH-) and the terminal methyl (-CH3) group from the three fatty acyl chains. Consequently, chemometric equations based on the integral values of the 1H-NMR resonances allow for the calculation of the mean molecular weight of triacylglycerol species, leading to the determination of the number of moles of triacylglycerol species per 1 g of fat and eventually to the calculation of the saponification value (SV), expressed as mg KOH/g of fat. The algorithm was verified on a series of binary mixtures of tributyrin (TB) and vegetable oils (i.e., soybean and rapeseed oils) in various ratios, ensuring a wide range of SV. Compared to the conventional technique for SV determination (ISO 3657:2013) based on titration, the obtained 1H-NMR-based saponification values differed by a mean percent deviation of 3%, suggesting the new method is a convenient and rapid alternate approach. Moreover, compared to other reported methods of determining the SV from spectroscopic data, this method is not based on regression equations and, consequently, does not require calibration from a database, as the SV is computed directly and independently from the 1H-NMR spectrum of a given oil/fat sample.
... The extracted lipid was subjected to find out the acid value according to the international standard ISO 660:2009 (Skiera et al., 2014). A simple acid-base titration was carried out by dissolving 0.1 g of extracted lipid in a 2:1 mixture of ethanol and diethyl ether and titrated against 0.1 M potassium hydroxide solution with phenolphthalein indicator. ...
This study focuses on the recovery of resources from Latvian dairy industrial wastewater.
Specifically, lipids are important resources from the wastewater, so the study aim is to check the quality of the wastewater through COD, BOD-5, total nitrogen, total phosphorus; to separate and characterize fatty acids through various chemicals and characterization (like FTIR, NMR, and GC- MS) techniques. The COD was found to be 1,680±20 mg L-1 and the BOD-5 was found to be 1,196±50 mg L-1, indicating that the dairy wastewater contains a considerable amount of oxidizable carbon. Also, spectral studies were done to identify the fatty acids in the wastewater. The FT-IR spectrum clearly showed the presence of C-O stretching at 1092 cm−1 and the 1H NMR indicated the peaks in the range 4.72-5.08 ppm and 5.43-6.33 ppm, confirming the presence of fatty acids. Total lipid content was extracted with solvent extraction method by using hexane, and it was found to be 5.2 g L-1. The acid value of the extracted lipids was found to be 56 mg KOH g- 1. Finally, GC-MS analysis confirmed the presence of palmitic acid, stearic acid, myristic acid, oleic acid, linolenic acid, lauric acid, and linoleic acids in the total lipid. Therefore, the extraction of lipids from dairy wastewater is paramount in the applications of biodiesel production.
Please cite this article as: Ekka, B., Mieriņa, I., Juhna, Tā., Turks, Mā., Kokina, Kristī., Quantification of different fatty acids in raw dairy wastewater, Cleaner Engineering and Technology (2022), doi: https://
... Analysis through spectral characteristics NMR spectroscopy Nuclear magnetic resonance spectroscopy finds use in the quality evaluation of edible oils by identifying the fatty acid constituents and other chemical parameters without the laborious steps in the classical wet lab methods. 17 In the proton nuclear magnetic resonance ( 1 H NMR) spectrum of Garcinia gummi-gutta seed oil (Fig. 1), the protons of unsaturated acyl chains appeared at ⊐ 1.99-2.00 integrating for seven protons, suggesting the presence of allylic methylene groups. ...
BACKGROUND
Edible oils are important in human nutrition and health. The demand for edible oils is increasing globally and the situation warrants identification of new natural sources of oils with proper quality and safety evaluation. Garcinia gummi-gutta is a widely cultivated fruit crop in Kerala, south India. The fruit rinds are the useful part, while the seeds are treated as waste material. With this background, the composition, physico-chemical properties, and preliminary toxicity studies of the seed oil were evaluated with a view to find a utility of the oil in the food sector.
RESULTS
Garcinia gummi-gutta seed oil yield was 33.53% 335.30 g kg⁻¹ w/w. Physico-chemical parameters of the oil were determined through NMR studies. The values are in good agreement with that of conventional edible oils. The saturated fatty acid stearic acid has been identified as the prominent component (55.39%) followed by the monounsaturated oleic acid (40.22%) through GC-MS analysis of FAMEs. Preliminary in vivo acute oral toxicity studies and acute dermal toxicity studies on female Wistar rats, and dermal irritation studies on New Zealand white male rabbits showed no morbidity, mortality, appreciable change in the body weight, or clinical signs of dermal responses.
CONCLUSIONS
The results suggest the seeds of G. gummi-gutta as a rich source of edible oil. Presence of the stable fatty acid stearic acid as the major constituent recommends the use of oil in value added food products such as chocolates. Preliminary toxicological studies also recommend the use of oil in food and cosmetic sectors.
This article is protected by copyright. All rights reserved.
... The presence of FFA has been confirmed by the singlet at 13.26 ppm in the 1 H NMR spectra of the raw fats, which broadened by addition of DMSO-d 6 (about 5% v/v) due to fast proton exchange processes. No signals in the low-field region due to hydroperoxides were present [82]. ...
Three different waste animal fats (bone, chicken, and tallow) have been studied to evaluate whether they could be used as bioliquids according to the European Regulation (EC) No.1069/2009. The analyses showed that they contained an unsuitable amount of free fatty acids (FFA) and impurities content (total sediment) if compared with the standards for power generation (set by UNI 6579:2009), with the exception of tallow fat (class C, UNI/TS 11163:2018). A series of physical-chemical processes already applied at industrial scale have been considered to manage the acid value and the impurities content. The FFA esterification was carried out with methanol, comparing two acid catalysts (sulfuric acid or Amberlyst – 15), followed by neutralization of the residual acidity with two different bases (ammonia solution or solid sodium carbonate monohydrate) when necessary. The final purification has been achieved by treatment with powdered activated carbon. In particular, the bone fat was studied as reference material, having the worst initial physical-chemical characteristics. The UNI/TS 11163:2018 standard would allow to classify the bioliquid from bone fat belonging to class B, while the one from chicken would require further degumming and purification processes to reduce the metals, sulfur, and phosphorus content.
... rate end points with dark oil samples is difficult. To overcome the disadvantages of titration analysis, a number of improved instrumental methods, such as automatic potentiometric titration method 4 , colorimetric method 5 , flow injection analysis 6, 7 , high-performance liquid chromatography 8 , gas chromatography 9 , liquid chromatography 10 , Raman spectroscopy 11 , 1 H nuclear magnetic resonance 12, 13 , infrared spectroscopy, and near-infrared NIR spectroscopy 14 , have been developed as good substitute methods. These methods have significant advantages over titrimetric methods in terms of analysis speed and reduction of harmful solvents, but require relatively expensive instruments and professionals. ...
A Fourier transform infrared (FTIR) spectroscopy with infrared quartz cuvette (IQC) as spectral accessory method was developed to determine acid value (AV) of edible oils. The absorption peak at 5680 cm–1/5487 cm–1 ascribed to the C–H stretching band was a substitute for the peak of an internal standard. Partial least square (PLS) regression was used for AV calibration, and samples were validated by titrated method. Results showed dilution calibration was feasible for randomly dilution among 6–13:1 (CCl4: oils, v/v). PLS calibration was optimal by a spectral wavenumber (3603 cm–1–3250 cm–1) as the first derivative treatment. Correlation coefficient and root mean square error of calibration were 0.9967 and 0.135, respectively. Calibrated validation, blind sample validation and precision analysis presented a good correlation between IQC-FTIR and titrated methods. Based on the dilution calibration, randomly diluted oil samples can be employed by IQC-FTIR.
... mixture containing two parts nonpolar solvent (usually hexane or ethyl ether) and one part polar solvent (commonly ethanol), and is then titrated with a alkaline solution (Du et al., 2012). However, this method has a number of drawbacks, including errors during titration (often when using darker or lighter samples), solvent consumption, the time it takes to perform tests, and generation of residues (Skiera, Steliopoulos, Kuballa, Diehl, & Holzgrabe, 2014;Talpur et al., 2015). ...
This study investigated the application of infrared spectroscopy with multivariate calibration methods for at‐line monitoring of the degradation of soybean oil in industrial frying processes by determining when the acidity index and total polar materials (TPM). The infrared spectra (650–3,200 cm⁻¹) were acquired using the attenuated total reflection accessory (ATR‐FTIR), with a resolution of 4 cm⁻¹, and 16 scans. Partial least‐squares regression (PLS) models were evaluated for individual and simultaneous determination, and results were compared with reference methods. The individual calibration model showed standard error of prediction values of 0.09% (w/w) and 1.6% (w/w) for the acidity index and TPM, respectively. The simultaneous determination of the acidity index and TPM showed SEP values of 0.17% (w/w) and 1.6% (w/w), respectively. The results demonstrate that infrared spectroscopy combined with multivariate calibration techniques can be servant used in routine soybean oil quality control in industrial frying processes.
Practical applications
Foods prepared by the frying process are strongly influenced by the oil used in the process, since the product tends to absorb part of the oil during its cooking. This oil when used for a long period and exposed to high temperatures, end up suffering oxidation reactions, and can greatly reduce your shelf life. In this way the industries that use these processes for the manufacture of their products, apply a series of chemical analyzes in order to validate the quality of the oil used, these analyzes use a high amount of solvents and time. As an alternative to the use of these traditional analyzes, methods have been developed through the use of infrared spectroscopy combined with multivariate analysis tools, for the creation of partial least squares calibration models for the prediction of quality parameters of oils used in frying.
... The COOH peak could provide a unique signal in the 1 H spectrum for FFA, however, fast proton exchange processes with water in CDCl3 result in the broadening of the signal arising from the carboxylic acid group (COOH) at around 12 ppm, such that is not apparent in the spectrum. Skiera et al. (2014) investigated the FFA content in pharmaceutical lipids using NMR spectroscopy. Their method involved the addition of small amounts of deuterated dimethyl sulfoxide (DMSO-d6) to the fatty oils in CDCl3, which slowed the proton transfer sufficiently to allow the detection of the COOH signal. ...
Spent coffee grounds (SCG) are the main residues of the coffee industry, and a potentially valuable source of lipids for sustainable biodiesel production. However, feedstock properties, such as the high SCG moisture content and the relatively high free fatty acid (FFA) content of recovered oil, can impact on the efficiency of the extraction and the quality of extracted oil and derived biodiesel, thus reducing the possible environmental benefits of producing biodiesel from this waste stream. Therefore, a better understanding of feedstock properties and processing steps is required to improve the efficiency of SCG valorization as a biodiesel feedstock and contribute to its future industrialization. This work presents experimental studies including feedstock characterization of SCG, laboratory and pilot plant scale solvent extraction experiments and utilization of mechanical pressing for processing of coffee residues. The solvent extraction experiments investigated effects of solvent type, SCG moisture content and particle size, SCG-to-solvent ratio, and the duration, temperature and pressure of the extraction process on oil extraction efficiency and composition. Transesterification was performed with SCG oil containing high FFA content, and the combustion of derived biodiesel was investigated in a compression-ignition engine. Instant SCG were found to possess higher lipid and FFA content than retail SCG. Solvent extraction experiments showed that longer durations, higher temperatures, low moisture presence and mixed size SCG particles generally improved extraction efficiency, while the impact of pressure depended on temperature. A correlation was observed between longer extraction durations and lower FFA content, while extraction temperature and solvent selection affected the oil composition. Pilot plant extraction showed reduced sensitivity to moisture, while mechanical pressing was efficient in removing a fraction of residual moisture. A two-step transesterification process achieved a biodiesel conversion yield of 86.7 % relative to initial oil weight. SCG biodiesel showed similar combustion and emissions characteristics to commercial soybean and rapeseed biodiesel.
... Nevertheless, a detection limit of 0.5% was obtained. A very elegant approach to quantify free fatty acids in edible oil was demonstrated by Skiera et al. [47][48]. When the oil is dissolved in a CDCl 3 : DMSO mixture (the optimal ratio is 5: 1), the COOH signal appears as a sharp singlet around 11.6 ppm. ...
This chapter reviews the use of NMR for compositional and quantitative analysis of oils and lipids in food. The literature of the past decade on the following topics is reviewed: High-resolution ¹³C NMR is a powerful method to determine the positional distribution of different classes of fatty acids on the glycerol backbone due to chemical shift differences observed on the carbonyl signal. Oxidation products such as aldehydes, hydroperoxides, and epoxides can be observed and quantified directly in the ¹H NMR spectrum of lipids. Results agree very well with classical methods such as determination of anisidine value and peroxide value. The advantage of NMR lies in the additional information obtained and the ease of sample preparation and the speed of the analysis in general. Minor components of oils and lipids such as sterols, polyphenols, and glycerol can be quantified either directly or after derivatization. In addition, conjugated fatty acids and galactolipids are observed. By means of ³¹P NMR, it is possible to identify and quantify all known phospholipids using various extraction or preconcentration methods. Also, the concentration of diglycerides and monoglycerides in the lipid matrix can be determined in a straightforward way without timeconsuming sample pretreatment. High-resolution ¹H NMR is also a very useful technique to obtain information on the fatty acid composition of oils, albeit more restricted to classes of fatty acids: saturated, monounsaturated, and polyunsaturated. Such information can also be obtained by means of low-field NMR when combined with chemometric methods. Time-domain NMR, finally, is a fast and cost-effective method to assess total lipid content and water content and to obtain information on the physical state of these components. © Springer International Publishing AG, part of Springer Nature 2018.
... Nevertheless, a detection limit of 0.5% was obtained. A very elegant approach to quantify free fatty acids in edible oil was demonstrated by Skiera et al. [47][48]. When the oil is dissolved in a CDCl 3 : DMSO mixture (the optimal ratio is 5: 1), the COOH signal appears as a sharp singlet around 11.6 ppm. ...
This chapter reviews the use of NMR for compositional and quantitative analysis of oils and lipids in food. The literature of the past decade on the following topics is reviewed: High-resolution 13C NMR is a powerful method to determine the positional distribution of different classes of fatty acids on the glycerol backbone due to chemical shift differences observed on the carbonyl signal. Oxidation products such as aldehydes, hydroperoxides, and epoxides can be observed and quantified directly in the 1H NMR spectrum of lipids. Results agree very well with classical methods such as determination of anisidine value and peroxide value. The advantage of NMR lies in the additional information obtained and the ease of sample preparation and the speed of the analysis in general. Minor components of oils and lipids such as sterols, polyphenols, and glycerol can be quantified either directly or after derivatization. In addition, conjugated fatty acids and galactolipids are observed. By means of 31P NMR, it is possible to identify and quantify all known phospholipids using various extraction or preconcentration methods. Also, the concentration of diglycerides and monoglycerides in the lipid matrix can be determined in a straightforward way without time-consuming sample pretreatment. High-resolution 1H NMR is also a very useful technique to obtain information on the fatty acid composition of oils, albeit more restricted to classes of fatty acids: saturated, monounsaturated, and polyunsaturated. Such information can also be obtained by means of low-field NMR when combined with chemometric methods. Time-domain NMR, finally, is a fast and cost-effective method to assess total lipid content and water content and to obtain information on the physical state of these components.
... The amount of free fatty acids in oil can be determined from the areas of the carboxylic group proton (COOH) signal appeared at 11-12 ppm and the methylene proton signal directly adjacent to the carboxyl group resonating and 2.2-2.4 ppm in the 1 H NMR spectrum obtained from oil dissolved in a mixture of CDCl 3 and DMSO-d 6 (5:1, v/v) (Skiera et al. 2012b(Skiera et al. , 2014. In the test with a total of 305 oil and fat samples, the NMR method showed a very strong correlation with the conventional method except for hard fat that showed somewhat significant deviations, the data obtained by the two methods were in good agreement. ...
The 31P NMR spectroscopy is not as frequently used as other NMR techniques. However, it can be very useful in case where strong signal overlap and dynamic range problems in 1H NMR spectra and/or long relaxation time of 31C NMR become a problem. It is known to be a better analytical method than time-consuming HPLC and TLC techniques in analyses of phospholipids in oil. The 31P NMR spectroscopy can also be used to determine the fatty acid distribution and to assess the oxidation of vegetable oils. The major drawback of 31P NMR is that the experimental procedure involves an additional step, the derivatization of functional groups in the oil sample with a phosphorus reagent. One of the major uses of this technique is to distinguish structurally similar compounds such as mono-, di-, and triacylglycerols.
... The amount of free fatty acids in oil can be determined from the areas of the carboxylic group proton (COOH) signal appeared at 11-12 ppm and the methylene proton signal directly adjacent to the carboxyl group resonating and 2.2-2.4 ppm in the 1 H NMR spectrum obtained from oil dissolved in a mixture of CDCl 3 and DMSO-d 6 (5:1, v/v) (Skiera et al. 2012b(Skiera et al. , 2014. In the test with a total of 305 oil and fat samples, the NMR method showed a very strong correlation with the conventional method except for hard fat that showed somewhat significant deviations, the data obtained by the two methods were in good agreement. ...
The NMR method has drawn great interest as a new method to assess the level of lipid oxidation since most of conventional analytical methods have some problems. The 1H NMR method monitoring the disappearance of starting materials was found to be very reliable for the assessment of lipid oxidation. In this chapter, the development of 1H NMR methods for the assessment of lipid oxidation during storage and frying will be discussed. Starting from the first method reported by Saito in 1987, a variety of 1H NMR methods developed by many research groups are introduced in this chapter. Early studies focused more on lipid oxidation at relatively lower temperatures such as storage temperatures or slightly higher temperatures for the acceleration of oxidation (25–70 °C) since the more oxidation products could be detected at a lower temperature. Later, it was found that there were significant differences between oxidation products and oxidation mechanisms with different oxidation temperatures. There are four different types of methods developed for the assessment of oxidation during frying: 1) Methods monitoring the changes of major NMR signals, 2) methods using the NMR proton relaxation time, 3) methods measuring acyl groups, and 4) methods measuring aldehydes and other oxidation product.
... The amount of free fatty acids in oil can be determined from the areas of the carboxylic group proton (COOH) signal appeared at 11-12 ppm and the methylene proton signal directly adjacent to the carboxyl group resonating and 2.2-2.4 ppm in the 1 H NMR spectrum obtained from oil dissolved in a mixture of CDCl 3 and DMSO-d 6 (5:1, v/v) (Skiera et al. 2012b(Skiera et al. , 2014. In the test with a total of 305 oil and fat samples, the NMR method showed a very strong correlation with the conventional method except for hard fat that showed somewhat significant deviations, the data obtained by the two methods were in good agreement. ...
There are a variety of analytical methods developed for the determination of lipid oxidation. However, many of them are old methods that depend on chemical reactions with a reagent, require long time and extensive labor, cannot be automated, measure only one kind of oxidation product, determine the concentration of an oxidation product that reaches a peak in a short time, and/or have inconsistencies due to multiple variations in the procedure. Modern analytical instruments, which can handle many samples at a time by automation, concomitantly detect many oxidation products, and be used for a long period of oxidation process, should be utilized to overcome the problems of current standard analytical methods. The NMR methods meet all these needs and should be more widely used for the analysis of lipids. More convenient, user-friendly NMR instruments such as small benchtop NMR instruments and software programs such as an automated analysis program for the fatty acid composition of vegetable oils have been developed.
... The amount of free fatty acids in oil can be determined from the areas of the carboxylic group proton (COOH) signal appeared at 11-12 ppm and the methylene proton signal directly adjacent to the carboxyl group resonating and 2.2-2.4 ppm in the 1 H NMR spectrum obtained from oil dissolved in a mixture of CDCl 3 and DMSO-d 6 (5:1, v/v) (Skiera et al. 2012b(Skiera et al. , 2014. In the test with a total of 305 oil and fat samples, the NMR method showed a very strong correlation with the conventional method except for hard fat that showed somewhat significant deviations, the data obtained by the two methods were in good agreement. ...
One of the most significant contributions of the 1H NMR technique is that it made major advances in elucidation of molecular structures of oxidation products. Since oxidation mechanisms and consequent oxidation products are different at different temperatures, this chapter is divided into two parts: 1) 1H NMR to indentify oxidation products during storage of oil and 2) 1H NMR to indentify oxidation products at frying temperatures. The study on oxidation products using 1H NMR was conducted as early as 1966 when Zimmerman utilized a very early model of the NMR instrument (60 MHz) to verify the isomerization of unsaturated hydroperoxide to a ketohydroxy compound. Since then, many oxidation products including hydroperoxides, aldehydes, ketones, alcohols, and epoxides were identified by the NMR method. One major difference between the oxidation products formed at relatively lower temperatures and at frying temperatures is that intermediate oxidation products such as hydroperoxides are not observed at frying temperatures because these intermediate oxidation products easily react with other compounds or decompose to produce secondary oxidation products. These intermediate products can be detected only when the oil was heated for a relatively short time at a frying temperature.
... The amount of free fatty acids in oil can be determined from the areas of the carboxylic group proton (COOH) signal appeared at 11-12 ppm and the methylene proton signal directly adjacent to the carboxyl group resonating and 2.2-2.4 ppm in the 1 H NMR spectrum obtained from oil dissolved in a mixture of CDCl 3 and DMSO-d 6 (5:1, v/v) (Skiera et al. 2012b(Skiera et al. , 2014. In the test with a total of 305 oil and fat samples, the NMR method showed a very strong correlation with the conventional method except for hard fat that showed somewhat significant deviations, the data obtained by the two methods were in good agreement. ...
Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful analytical tools to identify organic and bio-organic substances and to elucidate their chemical structures. Therefore, it has widely been used to analyze a variety of foods. Moisture content, solid fat content, fatty acid composition in lipid, free fatty acids, authenticity of edible oils, and the metabolic profile of sweet pepper can be analyzed by the NMR spectroscopy.
... Recently, pharmaceutical application of qNMR has obtained great attention, which is described by two excellent reviews [186,187] and is also demonstrated by lots of studies reported. In order to secure the drug quality, 1 H qNMR is generally exploited for content determination of APIs, such as diquertin [167], iobitridol [171], and for quantitative analysis of excipients, such as lactose [179], pharmaceutical lipids [180], and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) [181]. Liang et al. [170] proposed a qNMR method for reliable content determination of clindamycin phosphate (CLP) tablets, which contained about 45% APIs. ...
The unique analytical capabilities of both identification and quantification of compounds in complex mixture by NMR technique have been demonstrated. qNMR is widely applied as routine analytical tool for the mixtures because of the universal existence of NMR-active nuclei. qNMR is one of the few standard-free quantification methods. It can quantitatively analyze multiple compound mixtures without requirement of chemical identical standards. In this review, theoretic background and technical keynotes on qNMR data acquisition, spectral processing, and signal deconvolution/integration will be discussed for quantitative analysis of multiple compound mixtures. Sample preparation and the effect of different sample conditions on the assessment of the concentration will also be discussed. ¹H 1D qNMR is the most often used method for quantitative analysis of multiple compound mixtures, yet heteronuclear 1D and 2D qNMR approaches have been increasingly recognized and exploited for quantitative assessment or concentration measurement. Some often used quantitative NMR methods are then summarized. Afterwards, applications of qNMR in the areas of metabolomics, natural products, traditional Chinese herbal medicine (TCM), pharmaceutical research and food analysis are exemplified. Finally, we prospect the future developments and applications of qNMR.
... The acid dissociation constants (pKa) in two propionic acid side chains in biliverdin and bilirubin have been determined based on chemical shifts in different pH solutions by 13 C NMR spectroscopy, which allows direct observation and quantitative measurement of the carboxylic acid and carboxylate anion carbon signals [19]. Over the last few decades, NMR has gained popularity for evaluation of the pKa and the quality of drugs, method validation, and the reference standard qualification [20][21][22][23][24][25]. ...
An apomorphine sublingual tablet formulation under development contains mixtures of apomorphine freebase (FB) and apomorphine hydrochloride salt. It is important to have a reliable analytical method to determine the ratio of the base and salt forms to ensure accuracy, reproducibility and robustness of the manufacturing processes as well as to meet the requirements of the quality target product profile. A Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy method based on the proton shift of the amine methyl group (N-CH3) in apomorphine has been developed to determine the mole percentage of freebase to the total mole of freebase and hydrochloride salt in the drug product. The method was evaluated in terms of specificity, linearity, and variability. The presence of excipients does not interfere with the analysis. A standard calibration curve of the chemical shift as a function of the proportion of freebase forms of apomorphine was established, covering the range of 100% apomorphine freebase to 100% apomorhine hydrochloride. The correlation coefficient (r2), slope, and Y-intercept of the regression line are 0.998, −0.00596, and 3.191, respectively. The day-to-day variability of the 1H shift in two instruments in the standard is less than 1% RSD. Three lots of the sublingual tablet drug product were examined and quantified by the standard. The mole percent apomorphine freebase was determined to be 73.8%, 75.2%, and 76.2%, respectively, within 100.0% ± 2.0% of the target value of 75.0%. The method is a new avenue to use the 1H NMR technique for determination of apomorphine freebase and salt ratio in a solid drug product dosage form for release testing and in-process control.
... Determination of free fatty acids in pharmaceutical lipids by 1 H NMR and comparison with the classical acid value (AV) was achieved. Investigations showed that, for fatty oils, the NMR method was suitable to reproduce the results of the classical AV method (Skiera et al., 2014). Quantitative NMR analysis provided the fatty acid chain profiles of the total lipid extracts. ...
Oxidative stability is one of the most important indicators for maintaining the quality of edible oils. 1H NMR fingerprinting is used to evaluate the stability of edible oils at room temperature. The assignments of the 1H NMR signals of the major and minor components of unoxidized edible oils and the oil stability prediction were given. Minor components of the oils are playing an essential role in defining oil authenticity and quality. Extra virgin olive oil (EVOO) showed β-sitosterol, whereas, moringa oil (MO) showed β-sitosterol and stigmasterol. MO showed nonglyceride fraction, aliphatic chains and olefins. Sunflower oil (SO) could be easily distinguished due to its high linoleic acid content followed by apricot kernel oil (AKO). The order of stability of edible oils under study was: MO > EVOO > AKO > SO. 1H NMR spectral data agreed with the results obtained from Rancimat method for the determination of oxidative stability of edible oils under study. The main advantages of this method are the short time of analysis, the possibility to analyze samples without any preliminary treatment, and the small quantity of sample required.
... Analysis through spectral characteristics NMR spectroscopy Nuclear magnetic resonance spectroscopy finds use in the quality evaluation of edible oils by identifying the fatty acid constituents and other chemical parameters without the laborious steps in the classical wet lab methods. 17 In the proton nuclear magnetic resonance ( 1 H NMR) spectrum of Garcinia gummi-gutta seed oil (Fig. 1), the protons of unsaturated acyl chains appeared at ⊐ 1.99-2.00 integrating for seven protons, suggesting the presence of allylic methylene groups. ...
The fatty acid composition is a parameter that determines the quality and origin of vegetable oils. The standard method used in the analysis of fatty acid composition is gas chromatography (GC). In the last 20 years, however, the ¹H NMR method has become more important in the analysis of fatty acids. Thanks to no need of special sample preparation, the high speed of analysis and the possibility to automate the process of analysis, ¹H NMR is becoming a popular method of testing vegetable oils. It is possible to test oils both qualitatively and quantitatively, taking into account both the fatty acid profile and the level of minor components. In combination with statistical and chemometric methods, the analysis of ¹H NMR spectra allows one to obtain much valuable information about the tested oil, considering its composition, quality, the presence of impurities, or the origin. The paper presents an overview of publications focusing on the application of the ¹H NMR method in the profiling of fatty acids in vegetable oils.
Hemp oil is widely used in the food industry, and also in many other industries. It is characterized by a high content of unsaturated fatty acids with the optimal ratio of ω-6 to ω-3 fatty acids (3:1). Such composition means that this oil is often used in the food, pharmaceutical and cosmetic industries. Due to the popularity of hemp oil and its high content of unsaturated fatty acids, methods for the quick oil quality analysis are sought. Six samples of cold-pressed hemp oil were stored under different conditions (2-8°C and 30°C) for one month and then their ¹H NMR spectra were recorded. The chemometric methods of PCA and OPLS-DA were used to perform the analysis of the spectra. The combination of those methods made it possible to observe the differences in the oil samples after a month of storage. Based on the ¹H NMR spectra, it was possible to differentiate the time and conditions of the oil storage.
Lipid oxidation is one of the main causes of degradation in food emulsions. It leads to the generation of off-flavors and a concomitant reduction in shelf-life of the food products. The multiscale complexity of lipid oxidation reactions in food emulsions has raised the need to develop new methodological approaches. In this chapter, we will discuss how the recent analytical advancements have opened new avenues for the identification and quantification of multiple key oxidation products and for the spatio-temporal resolution of the reactions. After shortly introducing the challenges related to lipid extraction prior to analysis, we will first focus on the use of electron spin resonance for the early assessment and of nuclear magnetic resonance for the simultaneous analysis of multiple oxidation products. Then, we will discuss the potential of chromatographic and mass spectrometry approaches to monitor non-volatile and volatile oxidation products and assess the contribution of minor surface-active lipid species. Finally, the recent developments in electron and fluorescence microscopy to monitor the structural changes associated with lipid oxidation and the localization of the reaction sites in emulsions will be discussed.KeywordsExtractionVolatilesMagnetic resonanceChromatographyMass spectrometryMicroscopyMechanistic insights
To investigate the effect of gamma (γ) irradiation on the water migration and lipid degradation of Micropterus salmoides (MS), the MS meat were cold-air dried for 0, 2, 4, 6, 8 and 10 hours, treated by γ ray from the Cobalt 60 at a dose of 3.36 kGy, then stored for 21 days. The low-field nuclear magnetic resonance (LF-NMR) results showed that the fresh MS meat contained immobile water at 86.33–89.80%. After drying and irradiation, the single amplitude and transverse (T2) relaxation times of the immobilized water decreased. During the storage, the MS meat in irradiation group can keep quality for 21 days, and T21 showed no changes during the whole period. At the results of irradiation on lipid degradation, the acid value (AV) shows drying-time dependent decrease, while the peroxide value (PV) changes conversely. Lower malondialdehyde (MDA) content was found in the MS meat dried for 4–6 hours than the cases of other groups (p＜0.05). After irradiation, ten fatty acids were detected in fresh MS meat and lower loss of fatty acid types were found in the MS meat dried for 4 hours. Among these fatty acids, palmitic acid (C16:0) and oleic acid (C18:1) exhibited higher proportion at 18.33%–25.66% and 36.6%–51.28%, respectively. In the work, the MS meat dried for 4 hours, containing about 37% water, is more tolerant to γ irradiation than the fresh or the over-drying MS meat.
The charged aerosol detector (CAD) is an aerosol-based detector employed in liquid chromatography which has become established in the field of pharmaceutical analysis due to its outstanding performance characteristics, e.g. the almost uniform response for nonvolatile analytes. Owing to its principle of detection, the response of the CAD depends on the volatility of a compound and is inherently nonlinear. However, the newly implemented instrumental settings evaporation temperature and power function value (PFV) are valuable tools to overcome some of these drawbacks and can even enhance the detector’s capabilities when adjusted properly. This thesis aimed to evaluate the impact of the new instrumental settings on the CAD performance. Additionally, the influence of modern separation techniques for small polar compounds on the CAD was assessed and the applicability of hyphenated UV-CAD techniques explored. The optimization strategies derived from the evaluation procedures and the conjunction of the instrumental and chromatographic techniques investigated were utilized for the challenging impurity profiling of amino acids and amino acid-like drugs. The results of the method validation procedures confirmed the broad applicability of the CAD in the pharmaceutical analysis of nonvolatile compounds, supported by satisfactory sensitivity and reproducibility for meeting the regulatory requirements with respect to the ICH guidelines Q2(R1) and Q3A(R2). The limits of applicability include the analysis of semivolatile compounds, and the method transfer between current and legacy CAD models. Further advances in the definition and standardization of allowed ranges for the instrumental settings and the establishment of general optimization procedures in the method development could lead to a more widespread use of the detection technique in compendial methods.
BACKGROUND
Irradiation can cause lipid oxidation of fish. This study aimed to examine the effect of radiation (method, dose, and dose rate) on the acid value (AV), peroxide value (PV), thiobarbituric acid reactive substances (TBARS) content, and fatty acid profile of fresh and freeze‐dried largemouth bass fleshes.
RESULTS
The AV, PV and TBARS presented dose dependent increase in fish meat for both cobalt‐60 (⁶⁰Co) and electron beam (EB) irradiation. With a 6 kGy of radiation, all measured indices in ⁶⁰Co group were significantly higher than those in EB group (P<0.05 or P<0.01). With a 3 kGy of radiation, the AV, PV and TBARS in 200 Gy/min dose rate group were significantly lower than those in 2 Gy/min and 80 Gy/min groups (P<0.05). After ⁶⁰Co irradiation, the AV, PV and TBARS in most of fresh samples were significantly higher than those in freeze‐dried samples (P<0.01). And ⁶⁰Co radiation decreased the unsaturated fatty acid (UFA) content in fresh samples and increased the UFA content in freeze‐dried samples. Our study indicated that ⁶⁰Co irradiation, particularly at a low dose rate, accelerated lipid oxidation in fish meat. A large amount of muscle moisture enhances the amount of UFA loss in fish meat during ⁶⁰Co irradiation.
CONCLUSION
Low dose (3 kGy) of EB irradiation, high dose rate (200 Gy/min) of ⁶⁰Co irradiation or freeze‐drying treatment can alleviate the lipid oxidation of largemouth bass meat.
This article is protected by copyright. All rights reserved.
Liquid chromatography has become the gold standard for modern quality control and purity analytics since its establishment in the 1930s. However, some analytical questions remain very challenging even today. Several molecules and impurities do not possess a suitable chromophore for the application of UV detection or cannot be retained well on regular RP columns. Possible solutions are found in derivatization procedures, but they are time consuming and can be prone to errors. In order to detect non chromophore molecules underivatized, the concept of aerosol based universal detection was established with the introduction of the evaporative light scattering detector (ELSD) in the 1970s and the charged aerosol detector (CAD) followed in 2002. These two challenging fields – polar and non chromophore molecules – are tackled in this thesis. An overview of applications of the CAD in the literature and a comparison to its aerosol based competitors and MS is presented, emphasizing on its high sensitivity and robustness. Parameters and techniques to overcome the drawbacks of CAD, such as the use of gradient compensation or adjusted evaporation temperatures are discussed. A consideration of aspects and drawbacks of data transformation such as the integrated power function value (PFV) in the GMP environment is performed. A method for the fatty acid analysis in polysorbate 80 that was developed on HPLC CAD was transferred to UHPLC CAD. Time and eluent savings of over 75% and 40%, respectively, as well as ways to determine the optimal CAD parameters resulted from this investigation. The evaporation temperature was determined as the most crucial setting, which has to be adjusted with care. Optimal signal to noise ratios are found at a compromise between maintaining analyte signal and reducing background noise. The incorporation of semi volatile short chain fatty acids enabled the observation of differences based on volatility of the analyte. E.g. for semi volatiles, an improved linearity by means of adjusting the PFV is achieved at values below 1.0 instead of at elevated PFVs. Using sugars and sugar related antibiotics, a proof-of-concept was given that artificial neural networks can describe correlations between the structure and physicochemical properties of molecules and their response in CAD. Quantitative structure property relationships obtained by design of experiment approaches were able to predict the response of unseen substances and yielded insights on the response generation of the detector, which heavily relies on the formed surface area of the dried particle. Further work can substantiate upon these findings, eventually building a library of diverse eluent compositions, analytes and settings. In order to cope with a chromatographically challenging substances, the application of ion pairing reversed phase chromatography coupled to low wavelength UV detection has been shown as a possible approach for the amino acid L asparagine. A method capable of compendial purity analysis in one single HPLC approach, thus making the utilization of the semi quantitative TLC-ninhydrin analysis obsolete, resulted from this. One cyclic dipeptide impurity (diketoasparagine) that was formerly not assessed, could be identified in several batches and added to the monograph of the Ph.Eur. Studying ibandronate sodium with CAD and ELSD, it was found that randomly occurring spike peaks represent a major flaw of the ELSD when high sample load is present. The research with this non chromophore bisphosphonate drug furthermore shed light on possible drawbacks of mixed mode chromatography methods and ways to overcome these issues. Due to strong adsorption of the analyte onto the column, over ten injections of the highly concentrated test solution were found to be necessary to ensure reproducible peak areas. Preconditioning steps should thus be evaluated for mixed mode approaches during method development and validation. Last, using a ternary mixed mode stationary phase coupled to CAD, a method for the impurity profiling of pamidronate disodium, also applicable to the assessment of phosphate and phosphite in four other bisphosphonate drugs, has been developed. This represents a major advantage over the Ph.Eur. impurity profiling of pamidronate, which requires two different methods, one of which is only a semi quantitative TLC approach.
In this study, magnetic amino-modified silica nanospheres (Fe3O4@SiO2@NH2) were prepared via coating 3-aminopropyltriethoxysilane onto the surface of Fe3O4 magnetite and applied to extraction of free fatty acids (FFAs) from edible oil samples for the first time. The Fourier transform infrared spectroscopy and vibrating sample magnetometer analysis indicated that Fe3O4@SiO2@NH2 was successfully synthesized and exhibited superparamagnetism. The static and dynamic adsorption experiments showed that the Fe3O4@SiO2@NH2 exhibited rapid adsorption equilibrium and satisfied adsorption capacity towards FFAs. Under optimized adsorption and analytical conditions, the Fe3O4@SiO2@NH2 could effectively enrich FFAs from edible oil samples with excellent linearities (0.2-1000 nmol g-1), extremely low limit of detections (0.09-0.46 nmol g-1), satisfactory recoveries (77.4-101.8%) and precisions (3.1-9.6%). Moreover, compared to classic solid phase extraction by commercial cartridge, the current magnetic solid phase microextraction method has many advantages including easier preparation of adsorbents, simpler sample handling procedure and less cost consumption. Therefore, this method provides a promising alternative to the traditional method for the analysis of FFAs to ensure the sanitation and quality of oils.
To effectively determine acid values (AVs) of edible oils by UV-vis spectroscopy, a novel method is developed based on two characteristic peaks of tetra-α-octyloxy zinc phthalocyanine at 709 and 749 nm. They are sensitive to trace fat acid in chloroform, and especially the one at 749 nm shows a good correlation between absorbance (AR) and fat acid concentration (cb). The functional relation can be expressed as AR = 0.08052lncb + 1.01100 suitable for common edible oils with AVs 0.06-2.40 mg KOH g-1. The analytical performance only needs 50 μL, about a drop, of edible oil mixed in 3 mL solution of the phthalocyanine compound in chloroform (1.0×10-5 mol•L-1) to record AR and then calculate cb from which AV is determined. For the edible oils with larger AVs exceeding 2.40 mg KOH g-1, they can be diluted and analyzed by the UV-vis method. As for those with minimal AVs no more than 0.06 mg KOH g-1, the AVs of them can be obtained by another supplemented equation AR = 3429.3cb + 0.073951, applicable to the range of 0.0024-0.06 mg KOH g-1. The UV-vis method is not only more convenient in determination on AVs of edible oils but also hardly disturbed by color of them in general, and thus it has a great potential for application in the analysis of oil products.
Saponification value (SV) is one of the parameters used to evaluate the quality of edible oils and it is determined by titration after oil heating with the KOH solution. This method is time-consuming, and requires a high amount of reagents and energy to perform the analysis. In the present work, the determination of SV is proposed using thermal infrared enthalpimetry (TIE) in a high-throughput and green way. Sample preparation and determination steps were performed in the same vessel (polypropylene microplate), which was adapted for the simultaneous preparation of 24 samples and determination of the remaining KOH by TIE. The optimization of such parameters as the sample mass, heating time, stirring speed and dispensing rate was performed and the best conditions found were 120 mg, 5 h, 250 rpm and 0.57 mL s-1, respectively. Afterwards, the SVs of canola, corn, olive, rice, soy and sunflower oil were determined by TIE and the results were compared with those obtained by AOAC 920.160, with no statistical differences found (Student’s t-test, p > 0.05). A decrease in the sample mass and reagent consumption of up to 41 times was observed. Additionally, TIE allowed a sample throughput at least two orders of magnitude higher than the conventional method, showing its feasibility for routine analysis. In addition, a reduction in energy consumption of 625 times was observed. Therefore, the proposed TIE method allowed the determination of the SVs of edible oils in a simple and high-throughput way in accordance with the principles of green analytical chemistry.
This chapter describes a number of basic methods for olive oil quality analysis. The role of these methods is to ensure that olive oils are consistent with the categories declared in terms of olive oil quality and to investigate olive oil adulteration or identity. The degree of triacylglycerol (TAG) hydrolysis, degree of oxidation, and compositional analysis are the three main categories of the parameters used for this assessment. The characteristics of olive oil and the relevant methods of analysis are described by the legislation of the EU Commission Regulation. Acidity determination in olive oils is of much interest, mainly because it is related to the quality and authenticity of the oils, while increased values increase the risk for oil oxidation. The determination of phytosterols is one of the most important markers for the detection of adulterated olive oils. In general, the sterols in olive oil were analyzed using gas chromatography (GC).
A new method for determining the acid values (AVs) of edible oils based on the O[single bond]H stretching band was developed. The oil sample was diluted with carbon tetrachloride and was placed in a quartz cuvette with a thickness of 1 cm to record the FTIR spectrum. The peak at 3535 cm−1, which corresponds to the O[single bond]H stretch of the carboxyl group in free fatty acids, together with the peak valley at 3508 cm−1 and the spectral data in the range of 3340–3390 cm−1 were used to determine the AV of the edible oil. The excellent linear relationship between the AVs measured in this work and those measured using a titration method, with a correlation coefficient (R) of 0.9929, indicates that the present procedure can be applied as an alternative to the classic method for determining the AVs of edible oils.
The consumption of fish oil-based dietary supplements has increased dramatically in recent years, which is mainly due to their high content of health promoting omega-3 fatty acids. However, these polyunsaturated fatty acids are extremely prone to oxidation. This study investigated the potential of 1H NMR spectroscopy for the assessment of the oxidative deterioration of fish oils. Nine raw fish oils of different fish species were stored for 3 months at room temperature at different degrees of sunlight exposure as well as under standardized accelerated storage conditions for 6 days (at 40°C and under constant light exposure). Fish oil samples were analyzed by 1H NMR spectroscopy as well as by traditional methods to determine the fat quality parameters peroxide value (PV), anisidine value (AnV), TOTOX value, and acid value (AV). PLS (partial least squares) regression models were used to predict these fat quality parameters based on the 1H NMR spectra. The best regression models reached an R2 of 0.949, 0.962, 0.991, and 0.977 for PV, AnV, TOTOX value, and AV, respectively. In conclusion, 1H NMR spectroscopy is a promising approach for a fast, reliable, and sustainable assessment of fish oil quality with regard to lipid oxidation. Practical applications: The results indicate a great potential of 1H NMR spectroscopy in the quality assessment of fish oils. This technology requires little time, work, amount of sample, and solvent and provides extensive information that can be obtained from a single spectrum. Such an approach is significantly more specific and detailed than traditional lipid oxidation parameters. Nine raw fish oils are stored under different conditions and analyzed by 1H NMR spectroscopy as well as by traditional methods to determine the lipid quality parameters peroxide value, anisidine value, TOTOX value, and acid value. Subsequently, PLS regression models are generated to predict these indices from the NMR spectra.
The purpose of this study was to evaluate the changes on the characteristics of the oxidative stability of Tenebrio molitor larvae during cold storage at 4^{\circ}C. Pretreatment for T. molitor larvae was designed into three methods: raw (R), freeze-dried (F.D.), and pan-fried (P.F.). The water content of the raw sample (61.46%) was higher than those of other samples (F.D.: 5.02%, P.F.: 3.67%) and its high water content was expected to facilitate the oxidation of the raw sample. In our results, the peroxide value and the carbonyl value of all of the samples increased and the raw sample, after storage for 18 day, showed the highest value. The pan-fried sample had no significant increase in its lactic acid content, acid value, and thiobarbituric acid value; whereas those values were increased in the raw sample and the freeze-dried sample (p
A nuclear magnetic resonance (NMR) spectroscopic method was tested to control twelve vitamins and accompanying substances in multivitamin preparations. The limits of detection (LODs) and limits of quantification (LOQs) varied in the 9.0-77.0 mg/kg and in the 34.5-93.5 mg/kg range respectively. The coefficients of variation (CVs) ranged between 0.9% and 12%. The 1H NMR spectra showed linearity for the 140-260 mg sample weight (R2>0.918). The NMR spectra of multivitamin preparations showed the presence of different degradation products of ascorbic acid. The NMR method was applied to thirteen different multivitamin preparations including tablets, capsules and effervescent tablets with average recovery rates between 85% and 132%. A number of accompanying substances (citric acid, mannitol, saccharin, cyclamate, sum of steviol glycosides and butylhydroxytoluene) were additionally identified and quantified. NMR was found to be suitable for the simultaneous qualitative measurement of water and fat soluble vitamins and accompanying substances, and shows some promise for quantitative determination of at least 5 vitamins (B1, B3, B5, B6 and E) in multivitamin preparations.
A novel 1H NMR method for the quantification of free fatty acid (FFA) content in vegetable oils, animal fats, and biodiesel is reported. Nonedible oils and animal fats, which are increasingly being explored as cheaper, renewable feed stocks for biodiesel production by transesterification with methanol, contain a significant amount of FFA along with other acidic impurities. The 1H NMR spectroscopic method is found to be more accurate than the conventional titrimetric analysis for the estimation of FFA content especially in those cases where acidic entities other than the FFA are also present in the feedstock. The titrimetric methods provide a gross acid value which corresponds to that of FFA and other acidic impurities. Our NMR method provides the FFA content exclusively. In the case of refined edible oils (wherein the other acidic impurities are negligible), the results obtained from the 1H NMR method are comparable with those from the titrimetic analysis.
Biologically active ingredients and excipients are the essentials of a drug formulation, such as a tablet, dragee, solution,
etc. Quality control of such substances thus plays a pivotal role in the production process of pharmaceutical drugs. Since
these agents often exhibit complex structures, consist of multiple components, or lack of a chromophore, traditional means
of characterization are often not feasible. Furthermore, substances of small molecular weight or strong polar character generally
exhibit poor chromatographic properties, thus, conventional procedures such as high-performance liquid chromatography are
often not applicable. Instead, quantitative nuclear magnetic resonance (qNMR) spectroscopy has emerged as an alternative or
orthogonal method in drug analysis. In this review, we elaborate on the application of qNMR to three important classes of
biological substances, namely polysaccharides, amino acids, and lipids, and demonstrate the benefits of this modern tool in
contrast to traditional techniques.
KeywordsQuantitative NMR spectroscopy–European pharmacopoeias–Active pharmaceutical ingredients–Heparin–Amino acid–Lipid
The chemical shifts, spin-lattice relaxation times (T
1), and one-bond C−H coupling constants of the glycerol carbons of mono-, di-, and triacylglycerols in CDCI3 solution are presented and discussed. The glycerol carbons have low T
1 values (<1.0 s) and full nuclear Overhauser effect and also exhibit broader linewidths than the aliphatic carbons, suggesting that the glycerol carbons are at or near the T
1 minimum for the dipole-dipole relaxation mechanism. Therefore, for quantitative measurement of the composition of partial acylglycerols (relative to the triacylglycerols) in palm oil, the nuclear magnetic resonance (NMR) spectrum of the β-carbons, which lie exclusively in the region δ68.3–72.1 ppm, should preferably be acquired at medium or low magnetic fields and at an elevated temperature in order to ensure that the condition for extremely narrow spectral lines is satisfied. The chemical shifts and spinlattice relaxation times of the aliphatic C-2 and C-3 carbons and of the carbonyl carbons (C-1) of acyl groups present in palm oil are also presented and discussed. The presence of free fatty acid in the palm oil is easily detected and quantified in the spectrum of the aliphatic carbons. The presence of partial acylglycerols in palm oil can also be detected and/or quantified in the NMR spectra of the C-2 and the carbonyl carbons. The quantitative analysis of the glycerol carbons of a known mixture of acylglycerols obtained by using this method is presented.
A user-interactive computer-assisted Fourier transform infrared (FTIR) method has been developed for estimation of free fatty
acids (FFA) in vegetable oil samples by deconvolution of the infrared (IR) absorbances corresponding to the triglyceride ester
and FFA carbonyl bonds. Peak areas were used to determine FFA as a percentage of the total carbonyl areas in weighed standards
of refined, bleached, deodorized soybean oil containing from 0 to 5% added oleic acid. These data for percent FFA by FTIR
were compared to corresponding FFA data obtained by two titration methods-the AOCS Official Method Ca 5a-40 and the Official
Method with a slight modification. Correlation coefficients were 0.999 for the Ca 5a-40, 0.999 for the modified and 0.989
for the FTIR methods. FFA in samples of crude soybean oils extracted from damaged beans (0.5 to 2.1% FFA) were measured by
FTIR and compared to data obtained by titration of the same samples (correlation coefficient, 0.869).
A new method for determining acid values in vegetable oils has been developed for a nontitration pH-metric technique with
a reagent consisting of 0.20 M triethanolamine in a 1∶1 solution of water and isopropanol. The emulsive properties of this
reagent provide rapid (within a minute) and quantitative extraction of free fatty acids from an oil into the solvent phase.
Acid values were determined by measuring conditional pH of the emulsified reagent in a pH-meter with an aqueous reference
electrode. Three different applications of this technique are discussed.
A new transmission-based Fourier transform infrared (FTIR) spectroscopic method for the direct determination of free fatty acids (FFA) in edible oils has been developed using the developed spectral reconstitution (SR) technique. Conventional neat-oil and SR calibrations were devised by spiking hexanoic acid into FFA-free canola oil and measuring the response to added FFA at 1,712 cm(-1) referenced to a baseline at 1,600 cm(-1)(1,712 cm(-1)/1,600 cm(-1)). To compensate for the known oil dependency of such calibration equations resulting from variation of the triacylglycerol ester (C═O) absorption with differences in oil saponification number (SN), a correction equation was devised by recording the spectra of blends of two FFA-free oils (canola and coconut) differing substantially in SN and correlating the intensity of the ester (C═O) absorption at the FFA measurement location with the intensity of the first overtone of this vibration, measured at 3,471 cm(-1)/3,427 cm(-1). Further examination of the spectra of the oil blends by generalized 2D correlation spectroscopy revealed an additional strong correlation with an absorption in the near-infrared (NIR) combination band region, which led to the development of a second correction equation based on the absorbance at 4,258 cm(-1)/4,235 cm(-1). The NIR-based correction equation yielded superior results and was shown to completely eliminate biases due to variations in oil SN, thereby making a single FFA calibration generally applicable to oils, regardless of SN. FTIR methodology incorporating this correction equation and employing the SR technique has been automated.
The role of Quantitative NMR (qNMR) spectroscopy in pharmaceutical applications are discussed. qNMR is linear over a wide concentration range and it seems to be more robust than the separation methods coupled to UV, fluorescence, CAD, NQAD, and ELSD. It requires minimal sample preparation and a readily available internal standard (IS). Simultaneous determination of content, detection of impurities, residual solvents and other additives is possible as long as a component contains the nucleus observed. While the pharmaceutical companies extensively apply qNMR in drug discovery and development they mostly use HPLC in routine quality analysis rather than qNMR. Recently, qNMR became the leading method for the purity analysis of unfractionated heparin sodium and calcium in the USP which was deliberately contaminated with anaphylactoid oversulfated chondroitin sulphate (OSCS). qNMR should be considered more often for quantification and quality control of drugs, excipients, agrochemicals, and food ingredients.
Phosphorus-31 nuclear magnetic resonance spectroscopy ( (31)P NMR) was used to differentiate virgin coconut oil (VCO) from refined, bleached, deodorized coconut oil (RCO). Monoglycerides (MGs), diglycerides (DGs), sterols, and free fatty acids (FFAs) in VCO and RCO were converted into dioxaphospholane derivatives and analyzed by (31)P NMR. On the average, 1-MG was found to be higher in VCO (0.027%) than RCO (0.019%). 2-MG was not detected in any of the samples down to a detection limit of 0.014%. On the average, total DGs were lower in VCO (1.55%) than RCO (4.10%). When plotted in terms of the ratio [1,2-DG/total DGs] versus total DGs, VCO and RCO samples grouped separately. Total sterols were higher in VCO (0.096%) compared with RCO (0.032%), and the FFA content was 8 times higher in VCO than RCO (0.127% vs 0.015%). FFA determination by (31)P NMR and titration gave comparable results. Principal components analysis shows that the 1,2-DG, 1,3-DG, and FFAs are the most important parameters for differentiating VCO from RCO.
spectroscopy is famous for structure elucidation of small and large molecules, such as peptides and small proteins. NMR can also be used for quantitative purposes, e.g., the determination of the content of a drug and of its low-level impurities. This is because the area of a signal is proportional to the number of nuclei giving rise to it. A prerequisite for quantification is a pure signal, i.e., no overlap with signals of the same or other compounds. Even though the chemical shift of an atom is mainly determined by its neighboring atoms, a signal can be moved using different solvents, different concentrations, and by means of shift reagents for signal separation. For quantification purposes, the acquisition and processing parameters have to be set carefully. Special attention has to be paid to the completeT 1 relaxation. Quantification can be achieved by means of relative or absolute methods, using either internal or external standards.
Here we describe a novel 1H NMR assay for the determination of FFAs in edible oils. The analytical performance of the NMR assay is similar to that of the commonly used acid value (AV) method. A total of 120 edible oil samples were analysed by both approaches. Except for pumpkin seed oil, showing slight deviations, there was a good compliance between the results obtained from the two methods.
Within the course of lipid peroxidation, hydroperoxides are formed as primary products. They can be used as analytical markers to assess the deterioration status of oils and fats. Here a new 1H-NMR assay to determine the hydroperoxide amount in edible oils is presented. We were able to show that the analytical performance of the method is similar to that of the commonly used peroxide value (PV) according to Wheeler. A total of 290 edible oil samples were analyzed using both methods. For some oil varieties considerable discrepancies were found between the results obtained. In the case of black seed and olive oil, two substances could be identified that cause positive (black seed oil) and negative (olive oils) deviations from the theoretical PV expected from the NMR values.
The present study was designed to assess the agreement between analytical methodologies based on 1H and 31P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.
The recently presented in-house validation concept developed on the basis of a variance component model is extended and optimised by basing it on a fractional factorial sampling scheme. The presented approach relies on a comprehensive mathematical model to assess simultaneously the in-house reproducibility and its components in addition to uncertainty-related performance characteristics like power functions and critical concentrations. The influence of individual factors and the corresponding uncertainties can be determined separately in a single experiment with optimum utilization of the generated data, in this way achieving a favourable ratio between costs and result.
The present study was designed to assess the agreement between analytical methodologies based on 1 H and 31 P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.
Lipids extracted from albacore tuna (Thunnus alalunga) were studied using high-resolution C-13 nuclear magnetic resonance (NMR) spectroscopy. Simultaneous quantitative determination of free fatty acids, lipid classes, and fatty acids alpha-beta positional distribution in triacylglycerols was obtained. Glyceride and phospholipid composition was studied using glyceryl resonances. Lipids extracted from fresh white muscles of Atlantic tuna had a different triacylglycerol and phospholipid content, related to fish weight. Free fatty acid carbonyl resonances were detected at the lower, field of the C-13 NMR carbonyl region and used for its quantitative determination. NMR data agreed with those obtained using UV spectrophotometry, showing that NMR is a suitable method to follow lipolytic alterations. The careful study of glyceryl and carbonyl resonances also leads to the direct determination of fatty acid alpha-beta distribution in triacylglycerols. The quantitative analysis of fatty acid composition and distribution was then achieved, and results obtained using high-resolution NMR were in good agreement with those obtained by gas chromatography. Polyunsaturated fatty acids showed a preferential location in the beta-acyl position, whereas monounsaturated fatty acids were found preferentially esterified in the alpha-position. The method may be used to monitor the composition and changes in fish lipids and oils during processing or storage.
A fast ultra high performance liquid chromatography (UHPLC)–electrospray ionization (ESI)–mass spectrometric (MS) method was developed for simultaneous analysis of free fatty acids (FFAs), monoacylglycerols (MAG), diacylglycerols (DAG), triacylglycerols (TAG), and their oxidized equivalents. Effect of elevated column temperature was studied in order to optimize the chromatography of closely eluting peaks and to reduce high back pressure formed in UHPLC. The elevated temperature enabled high flow rate, better mass transfer, and therefore more narrow peaks and better separation of the analytes. The new method was applied to the analysis of total lipid extracts of lipolysis samples prepared by an artificial digestion model in order to investigate oxidized lipids and changes in their profiles in the chyme. Over 150 compounds were identified from the extracts. The UHPLC–ESI–MS method was proved to be fast, highly selective, and sensitive. Compared to a previously used high performance LC–ESI–MS method, the new UHPLC–ESI–MS method was over five times faster and consumed one tenth of the solvents while producing comparable quantitative results.
Practical applications: Edible oils and fats contain mainly TAGs, the lipolysis of which produces FFAs and MAGs with minor DAG components. These compounds are susceptible to oxidation in the stomach, and therefore the analysis of the oxidation products is important. Fast determination of FFAs and acylglycerols is also important in quality control of biodiesel. Our new method enables accurate and sensitive determination of different molecular species present in digested and processed samples with minimal sample preparation requirements. In this respect, the new method is applicable to large scale and fast screening of biological samples for lipidomic and metabolomic studies.
Free fatty acids (FFAs) in edible oils are one of the most frequently determined quality indices during production, storage, and marketing. In this study, a simple, stable and sensitive method for the simultaneous determination of saturated and unsaturated FFAs from edible oils using 2-(11H-benzo[a]carbazol-11-yl)-ethyl-4-methylbenzenesulphonate (BCETS) as labelling reagent with fluorescence detection has been established. FFAs are derivatized by BCETS and separated on a reversed-phase Eclipse XDB-C8 column with a gradient elution. The results indicated that all FFAs were found to be given an excellent linear response with correlation coefficients of >0.9994. The detection limits at a signal-to-noise ratio of 3 were in the range of 0.22–1.06 ng/mL. When applied to Lycium barbarum seed oils, the developed method showed good reproducibility. The effect of extraction methods including supercritical CO2 and organic solvent extraction on the FFAs composition has also been investigated. Meanwhile, this method exhibits powerful potential for the trace analysis of short- and long-chain free fatty acids from edible oils, foodstuff and other complex samples.Research highlights► A precise HPLC method for free fatty acid analysis in edible oil has been developed. ► This pre-column derivatization method offered the exciting LOD of 0.22–1.06 ng/mL. ► Derivatization between BCETS and FFA was optimised by response surface method. ► Free fatty acid analysis in L. barbarum seed oil was first reported.
For some years, a special in-house validation concept according to the Commission Decision 2002/657/EC of the European Union
is employed. The validation concept is based on a variance component model, which allows to consider matrix- and operation-induced
deviations and to calculate critical concentrations for given α-errors. The approach relies on a comprehensive mathematical
model to asses simultaneously the in-house reproducibility and its components. One important component, the repeatability
standard deviation, is estimated by means of a power function of the Horwitz-type. In this study, several performance characteristics
were compared based on the use of four recommended estimations for the standard deviation depending on the concentration level
of the analyte. A special factorial design for calibration, considering three factors influencing the variance of the measurement
values, was applied for the determination of arsenic in surface water samples collected at several abandoned mining sites
in Germany. The advantageous applicability of the validation method presented for analytical procedures referring to environmental
tasks was demonstrated.
KeywordsIn-house validation–Variance component model–Repeatability standard deviation
Thirty-one samples of vegetable oils were analyzed for free fatty acid (FFA) concentration by titration against sodium hydroxide and by trimethylsilyl (TMS) derivatization followed by gas chromatography (GC). In preliminary experiments, two silylation chemistries and three GC stationary phases were tested for TMS fatty acid ester formation and separation. No ideal combination of conditions was identified; however, hexamethyldisilazane with an acid catalyst and a non-polar J & W DB-5 column were chosen for comparison of the two approaches. Over the range of FFA values studied (0.04-12%), the results from the two methods were highly correlated (R > +0.996) and were generally in good agreement. However, values from the chromatographic method were slightly lower than values obtained by titration for the crude oil samples (which had higher FFA levels). For oils with >0.4% FFA, the GC approach was slightly less reproducible (average coefficient of variance of ~3%) compared with the titration approach (average coefficient of variance of ~1.4%). For oils with <0.4% FFA, the coefficients of variance were higher (8-9%) and comparable between the methods.
This paper introduces a facile method to determine the amount of mono- and diglycerides in virgin olive oils. This method is based on the phosphorylation of the free hydroxyls of the mono- and diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the (31)P NMR spectrum. Quantitative (31)P NMR spectroscopy can be extended to the quantification of other constituents of olive oils bearing functional groups with labile protons.
A method validation approach that bases on a quadratic regression model in which two types of error are incorporated is presented and applied to an experimental data set. The validation approach enables the determination of analytical performance characteristics referred to in Commission Decision 2002/657/EC (i.e., repeatability, within-laboratory reproducibility, decision limit, detection capability).
European Department for the Quality of Medicines
- European Pharmacopoeia
European Pharmacopoeia, 7th ed., European Department for the Quality of
Medicines, Strasbourg, France, 2011, www.pheur.eu
Animal and Vegetable Fats and Oils-Determination of Saponification Value
ISO 3657:2002, Animal and Vegetable Fats and Oils-Determination of Saponification Value, 3rd ed., International Organization for Standardization, Geneva,
2002.