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Gas-liquid chromatography: the separation and identification of the methyl esters of saturated and unsaturated acids from formic acid to n-octadecanoic acid

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... Its extract reflects this context, bearing margaric acid (C 17:0 ), coprostanol and cholesterol derivatives in its composition, among other compounds (Table 1). Margaric acid occurs as a trace component of fat and milk fat of ruminants (James and Martin 1956;Hansen et al. 1957). Cholesterol is a compound characteristic of mammals (Gunstone 2004). ...
... Plant-derived sterols were also detected in part of the samples, indicating a vegetal component to the residues (Heron et al. 2010). Cholesterol and cholesterol oxidation by-products, as well as long unsaturated even-numbered fatty acids and odd-numbered carbon-chain fatty acids occurring in ruminant fats (James and Martin 1956;Heron et al. 2010Heron et al. , 2013 were missing for all extracts analysed but one. This single sample was coming from sewage and contained also coprostanol, an organic compound characteristic of faecal material (Bethell 1994;D'Anjou et al. 2012;Sistiaga et al. 2014). ...
... Its extract reflects this context, bearing margaric acid (C 17:0 ), coprostanol and cholesterol derivatives in its composition, among other compounds (Table 1). Margaric acid occurs as a trace component of fat and milk fat of ruminants (James and Martin 1956;Hansen et al. 1957). Cholesterol is a compound characteristic of mammals (Gunstone 2004). ...
... Plant-derived sterols were also detected in part of the samples, indicating a vegetal component to the residues (Heron et al. 2010). Cholesterol and cholesterol oxidation by-products, as well as long unsaturated even-numbered fatty acids and odd-numbered carbon-chain fatty acids occurring in ruminant fats (James and Martin 1956;Heron et al. 2010Heron et al. , 2013 were missing for all extracts analysed but one. This single sample was coming from sewage and contained also coprostanol, an organic compound characteristic of faecal material (Bethell 1994;D'Anjou et al. 2012;Sistiaga et al. 2014). ...
Article
This paper presents and discusses the results of residue analysis conducted on 78 ceramic lamps found in archaeological excavations in ancient Jerusalem, in an attempt to identify the types of oils used and the reasons for their preferential choice. The oil lamps chosen for the study were taken from a variety of contexts, which represent the different periods during which Jerusalem was settled and the different sectors of the city. The results of the study show that even the most mundane activity of lighting using oil held within it social and economic choices, as mirrored in the different excavation areas.
... Change of polar carboxylic group to less polar group through the alkylation or silylation [40] allow us to avoid FAs destruction, increase the volatility of the substances, give more useful mass-spectrometric information and increase the accuracy of peak identification, sensitivity, selectivity and do chromatographic separation using nonpolar and weak polar column phases better. Gas-chromatographic FAMEs determination using flame ionization detection (FID) [57,58] is well known from 1930s. The silylation provides determination of hydroxyl substituted acids and cyclic acids. ...
... There are alkaline and acidic methylation agents. Lipid esterification by methanol under presence of hard alkali [50,51,53,57,60] (saponification) is expressible (up to 2 min at normal condition) and allows us to get esters of triacylglycerides, glykolypids and phospholypids and other but results in PUFAs destruction and does not allows us to get free FAs esters. ...
Article
In a word, I have become cognisant of many, many things… but still I am not yet satisfied. My spirit still thirsts for further knowledge… St. John of Kronstadt Abstract-This paper presents a new technique of hydrocole (bacteria, blue−green algae, phytoplankton, zoo-plankton, sponges, fish oil and seal fat) fatty acids (FA) methyl esters determination by gas-liquid chromatography. The polyunsaturated fatty acids (PUFA) contents in these objects were different. The distinguishing features of the technique are the next ones: efficiency, lipid extraction recovery ≥94% using the sonication during 10-15 min without sample drying, high PUFAs yield (≥97%) by reduction of oxidation up to 40% during methylation; exhaustive extraction of fatty acid methyl esters (FAMEs) including PUFA; a new approach to obtain of methyl esters of free fatty acids except using toxic reagents; accuracy of FAMEs quan-tification including ω-3-, ω-6-, ω-9-FA using the din -decyl ether as an internal standard and accuracy of measurements using "T14165QC Fish oil" standard sample (first). The technique is approbated for Baikal hydrocole FA determination from 20 to 2000 μg in the sample and might be used for scientific and applied tasks. The interlaboratory precision of FAME determination of phytoplankton and bacteria is ≤10%.
... methyl cis-9-octadecenoate (9c-C18:1) and methyl trans-9-octadecenoate (9 t-C18:1), should be a feasible method for the analysis of trans fat acids in food. The early attempt for the separation of 9c-C18:1 and 9 t-C18:1 was reported by using of gas-liquid chromatography, but the separation has been a very difficult one to obtain [23,24]. Afterwards, RP-HPLC and Ag + -HPLC were successively applied for this separation. ...
Article
Based on our developed sodium hyaluronate-functionalized urea-formaldehyde (HA-UF) monolith, a silver nanoparticles-coated monolithic column has been fabricated via the interaction between silver nanoparticles (Ag NPs) and HA. The successful coating of Ag NPs on the parent monolith was proven by SEM, EDAX, UV–vis spectrum and XPS. Nitrogen adsorption desorption isotherms and Barret-Joyner-Halenda (BJH) pore size distributions of the parent and resultant monolith were also performed. Due to the Ag⁺-like affinity interaction caused by the contact of unsaturated compounds and Ag NPs, the Ag NPs-coated monolith showed satisfactory extraction efficiency towards these compounds, and was applied for in-tube solid-phase microextraction (SPME) of monounsaturated fatty acid methyl esters (MUFAMEs). Several factors for in-tube SPME, such as ACN percentage in the sampling solution, elution volume, sampling and elution flow rate, were investigated with respect to the extraction efficiency of model MUFAMEs. Under the optimized SPME conditions, a simple in tube SPME-Ag⁺-HPLC method for detection of model MUFAMEs has been proposed, the limits of detection (LODs) were less than 5.2 μg/kg, and the recoveries of spiked French fry samples were ranged from 86.6% to 96.1% with relative standard deviations (RSDs) less than 5.2%. This study provided an Ag NPs-coated monolith with good reproducibility and repeatable extraction performance, and developed an efficient method for in-tube SPME of MUFAMEs in practical food samples.
... The chromatographic separation of complex biological samples prior to the MS analysis is widely used to overcome the risks of ion suppression and improve the resolution of isobaric lipid species. Besides TLC, gas chromatography (GC) presents a powerful tool in lipid analytics, still well accepted in fatty acid profiling [34]. Derivatization of lipids, prior to GC analysis, however, might diminish structural information of more complex lipid species. ...
Article
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As a consequence of a sedentary lifestyle as well as changed nutritional behavior, today’s societies are challenged by the rapid propagation of metabolic disorders. A common feature of diseases, such as obesity and type 2 diabetes (T2D), is the dysregulation of lipid metabolism. Our understanding of the mechanisms underlying these diseases is hampered by the complexity of lipid metabolic pathways on a cellular level. Furthermore, overall lipid homeostasis in higher eukaryotic organisms needs to be maintained by a highly regulated interplay between tissues, such as adipose tissue, liver and muscle. Unraveling pathological mechanisms underlying metabolic disorders therefore requires a diversified approach, integrating basic cellular research with clinical research, ultimately relying on the analytical power of mass spectrometry-based techniques. Here, we discuss recent progress in the development of lipidomics approaches to resolve the pathological mechanisms of metabolic diseases and to identify suitable biomarkers for clinical application. Due to its growing impact worldwide, we focus on T2D to highlight the key role of lipidomics in our current understanding of this disease, discuss remaining questions and suggest future strategies to address them.
... Fatty acid methyl esters are usually prepared by firstly saponifying esterified fatty acids to free fatty acids and then re esterifying them to form methyl esters. The procedure was first established by James and Martin [4] and subsequently optimised by themselves and other authors [5,6] with the aim of reducing the polarity of the free fatty acids thus mak ing them easier to separate and quantify for the then newly developed gas liquid chromatography systems. The saponification step is usually carried out by heat treatment of the foodstuff in the presence of a strong alkali such as potassium hydroxide. ...
Article
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A microwave (MW) assisted rapid high through-put method for the preparation of fatty acid methyl esters (FAME) for the analysis of fatty acid profiles in a selection of foods was evaluated by comparing fatty acid profiles with those resulting from conventional FAME preparation. The microwave method gave fatty acid profiles in close agreement with those arising from conventional methods and the protocol gave acceptable recoveries (98–102%) and repeatability (RSDs for replicate analyses were 0.56–5.2%). In comparison to conventional methods the MW assisted method was simple, rapid and universally effective across foods ranging from dairy products to ready meals. EU regulation (No. 1169/2011) requiring declaration of the saturated, monounsaturated and polyunsaturated content of foods is placing pressure on processors and contract laboratories to analyse fatty acid profiles using relatively low through-put conventional methods. MW assisted preparation of FAMEs offers analysts a high-through-put, rapid and universal method to help overcome this potentially costly and labour intensive regulatory hurdle.
... But this method was relative simple and low experimental costs and it was still common used in many studies. With the development of GC, GC was available for the different fatty acid separation in simple mixtures [11]. However, the individual lipids of identification and quantification remained challenging in crude extract. ...
Article
The application of lipidomics, after genomics, proteomics and metabolomics, offered largely opportunities to illuminate the entire spectrum of lipidome based on a quantitative or semi-quantitative level in a biological system. When combined with advances in proteomics and metabolomics high-throughput platforms, lipidomics provided the opportunity for analyzing the unique roles of specific lipids in complex cellular processes. Abnormal lipid metabolism was demonstrated to be greatly implicated in many human lifestyle-related diseases. In this review, we focused on lipidomic applications in brain injury disease, cancer, metabolic disease, cardiovascular disease, respiratory disease and infectious disease to discover disease biomarkers and illustrate biochemical metabolic pathways. We also discussed the analytical techniques, future perspectives and potential problems of lipidomic applications. The application of lipidomics in disease biomarker discovery provides the opportunity for gaining novel insights into biochemical mechanism.
... Another common concept regarding the robust separation between animal fats and vegital oils state that cholesterol and cholesterol oxidation by-products, occurring in ruminant fats, are consistent with lipids of animal origin (James and Martin, 1956;Heron et al., 2010;Heron et al., 2013). ...
Article
During salvage excavations carried out in 2013 on behalf of the Israel Antiquities Authority, a seemingly isolated clay coffin with anthropoid lid was uncovered on the lower east slope of Tel Shadud in the Jezreel Valley (van den Brink et al., 2016). The coffin and associated funerary gifts bear strong resemblance to comparable specimens known foremost from Deir el-Balah in the Gaza strip and Bet She'an in the Jordan Valley. This new find should be placed within the context of the Egyptian New Kingdom colonization process of the region during the Late Bronze Age II and succeeding Iron Age I (van den Brink et al., In press). The coffin was systematically sampled for absorbed organic compounds along its profile. The results of the residue analysis reveals a particular burial aspect associated with pre-burial treatment of the coffin.
... But this method was relative simple and low experimental costs and it was still common used in many studies. With the development of GC, GC was available for the different fatty acid separation in simple mixtures [11]. However, the individual lipids of identification and quantification remained challenging in crude extract. ...
Article
The application of lipidomics, after genomics, proteomics and metabolomics, offered largely opportunities to illuminate the entire spectrum of lipidome based on a quantitative or semi-quantitative level in a biological system. When combined with advances in proteomics and metabolomics high-throughput platforms, lipidomics provided the opportunity for analyzing the unique roles of specific lipids in complex cellular processes. Abnormal lipid metabolism was demonstrated to be greatly implicated in many human lifestyle-related diseases. In this review, we focused on lipidomic applications in brain injury disease, cancer, metabolic disease, cardiovascular disease, respiratory disease and infectious disease to discover disease biomarkers and illustrate biochemical metabolic pathways. We also discussed the analytical techniques, future perspectives and potential problems of lipidomic applications. The application of lipidomics in disease biomarker discovery provides the opportunity for gaining novel insights into biochemical mechanism.
... In 1952, James and Martin published the first article on a procedure for GLC that revolutionized the analysis of fatty acids. Although it took some time for the method to become routine for milk fat analysis (James and Martin, 1956), it has become an essential tool for milk fat research (Patton et al. 1960;Smith, 1961). A useful illustration of the effect of GLC on understanding milk fat composition is to compare the reviews by Garton (1963) and Jensen (2002) on fatty acids in milk fat. ...
Article
Over 100 years, the Journal of Dairy Science has recorded incredible changes in the utilization of fat for dairy cattle. Fat has progressed from nothing more than a contaminant in some protein supplements to a valuable high-energy substitute for cereal grains, a valuable energy source in its own right, and a modifier of cellular metabolism that is under active investigation in the 21st century. Milestones in the use of fats for dairy cattle from 1917 to 2017 result from the combined efforts of noted scientists and industry personnel worldwide, with much of the research published in Journal of Dairy Science. We are humbled to have been asked to contribute to this historical collection of significant developments in fat research over the past 100 years. Our goal is not to detail all the work published as each development moved forward; rather, it is to point out when publication marked a significant change in thinking regarding use of fat supplements. This approach forced omission of critically important names and publications in many journals as ideas moved forward. However, we hope that a description of the major changes in fat feeding during the past 100 years will stimulate reflection on progress in fat research and encourage further perusal of details of significant events.
... Study 책임저자 5,6) . Thus, there is a need of development of simple and sensitive analytical method to determine fatty acids 7) Gas chromatography is the widely used techni- . FAs do not possesses chromophores so they cannot be measured by UV-Visible techniques 8) . . ...
Article
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Purpose: A sensitive gas chromatography mass spectrometry (GC-MS) method was developed for screening of fatty acid oxidation disorders. Methods: The assay utilized a simple protein precipitation with sulfosalicylic acid followed by tert -butyl dimethylsilyl (TBDMS) derivatization of hydroxyl functional group by N- tert -butyldimethylsilyl-N-methyltriflu - oroacetamide (MTBSTFA). Results: Calibration curves of spiked pooled plasma showed a linear relationship in the range of 0.01 ng -2 mg with correlation coefficient value greater than 0.98. Limits of detection (LOD) and limits of quantification (LOQ) were found in the range of 0.9-8.8 ng and 9-88 ng, respectively. Conclusion: The new developed method might be useful for a rapid, sensitive screening of inherited fatty acid oxidation disorders. In addition, the method expected to be one of the alternative method for screening newborns of metabolic disorders in the laboratories where expensive MS/MS is unavailable. Key words: Free fatty acids, Gas chromatography-mass spectrometry, tert -butyldimethylsilyl derivatives, Fatty acid oxidation disorders A sensitive determination of plasma free fatty acids following TBDMS derivatization using GCMS for screening fatty acid oxidation disorders.. Available from: https://www.researchgate.net/publication/321807985_A_sensitive_determination_of_plasma_free_fatty_acids_following_TBDMS_derivatization_using_GCMS_for_screening_fatty_acid_oxidation_disorders [accessed Feb 09 2018].
... 36 It was first reported in early 1950s that GC technology can be used for the separation of volatile compounds in a mixture. 37 In the mid 1950s, Roland S. Gohlke and Fred W. McLafferty at Spectroscopy Lab at Dow Chemical Co. worked in collaboration with Bill Wiley, Ian McLaren, and Dan Harrington at Bendix Labs, where they successfully produced the first direct-coupling GC-MS. ...
... -not analysis simultaneous, -different cathode lamp for different elements, -detects only metals and some non-metals, -only one element detected, -low precision (GF-AAS 1e5%, FA-AAS 0.1e1%), -only solution analysed, limited to the study of entire lipid classes was relatively simple with low experimental costs. With the development of gas chromatography, GC was available for the separation of different fatty acids in simple mixtures [87]. Chromatography of high separation capability was a necessary technique for extensive analysis of complex biological samples. ...
Article
Parkinson's disease (PD) is one of the most common neurodegenerative disorders, and is the second after Alzheimer's disease. This disease affects mostly older people, but an early onset of Parkinson's disease is observed in people aged 40–50 years. There are numerous theories about the specific causes of PD, but they have not yet been proved. Analytical methods are important in the determination of metabolites in biological samples from PD patients for the potential use as biomarkers of the disease. These biomarkers should allow early detection, precise prognosis or monitoring of disease progression. Metabolic profiling helps to understand the etiology of PD and aids in the development of new treatments. This review presents in a concise way a summary of the current status of the analytical methods used in establishing PD biomarkers, which can lead to a better understanding of the etiology of Parkinson's disease.
... The fatty acids from the various fractions were converted to their corresponding methyl esters by reaction with diazomethane. The esters were then identified by gas chromatography, as described by James and Martin (1956), James (1959), and Vorbeck et al. (1961aand Vorbeck et al. ( , 1963. ...
Article
Analyses of various lipid fractions of sections of cucumbers and of good and bloated dill pickles showed that marked changes occur in all lipid fractions during fermentation. The most striking difference noted was the decrease in the phospholipid fraction. A nearly fourfold increase in free fatty acid, as well as a marked increase in the neutral fat fatty acids and unsaponifiables, occurred. Gas chromatographic analyses of the methyl esters of fatty acids from the various lipid fractions yielded further interesting data. From the analyses, 41 esters were identified; however, 16 of the esters accounted for at least 95% of the acids. Among the marked changes were the increases in linoleic and linolenic acids in good pickles, in contrast to the increase in oleic acid in the bloated pickles. The presence of tridecenoic acid in cucumbers, and its absence in pickles; and the absence of caproic, caprylic, and capric acids in cucumbers, and its presence in pickles, were interesting. The data demonstrated that the lipid alterations that occur during fermentation of cucumbers are analogous to those previously reported for the sauerkraut fermentation.
... In mitochondria, proteins involved in fusion, division and degradation bind to phospholipids and the interactions generate a wide array of mitochondrial responses [65]. Cardiolipins are phospholipids located at mitochondrial inner membrane and critically involved in regulating mitochondrial structure, oxidative phosphorylation and biogenesis [66]. Structurally, cardiolipin consists of two phosphatidyl residues linked by a glycerol moiety and attached with a total of four fatty acyl chains [67]. ...
Article
The role of lipids in human health and disease is taking the center stage. In the last decades, there has been an intense effort to develop suitable methodologies to discover, identify, and quantitatively monitor lipids in biological systems. Recent advancement of mass spectrometry technology has provided a variety of tools for global study of the lipid “Omes”, including the quantification of known lipid molecular species and the identification of novel lipids that possess pathophysiological functions. Lipidomics has thus emerged as a discipline for comprehensively illuminating lipids, lipidderived mediators and lipid networks in body fluids, tissues and cells. However, owing to the complexity and diversity of the lipidome, lipid research is challenging. Here, the experimental strategies for lipid isolation and characterization will be presented, especially for those who are new to the field of lipid research. Because lipids are known to participate in a host of protein signaling and trafficking pathways, the review emphasizes the understanding of interactions between cellular components, in particular the lipid-protein interrelationships. Novel tools for probing lipid-protein interactions by advanced mass spectrometric techniques will be discussed. It is expected that by integrating the approaches of lipidomics, transcriptomics and proteomics, a clear understanding of the complex functions of lipids will eventually be translated into human diseases.
... These methods are time-consuming and require the use of large quantities of organic solvents. Since the development of gas-liquid chromatography (GLC) by James and Martin (1952), investigators have extracted the VFA with subsequent conversion to esters, usually methyl (James and Martin, 1956), prior to GLC analysis. ...
Article
Five gas chromatographic liquid phases (25% Carbowax 20 M plus 4% H3PO4, 17.5% dioctyl sebacate plus 7.5% sebacic acid, 17.5% dioctyl sebacate plus 7.5% docosanoic acid, 5% Tween 80, and 20% LAC-296 [poly (diethylene glycol adipate)] plus 2% H3PO4) were studied with respect to their utility in the separation and quantitation of steam-volatile organic acids commonly produced in fermentation. Optimal operating conditions and column stability for routine analysis were established. An Aerograph Hy-Fi gas chromatograph was used for all work, except the studies with Tween 80 in which an Aerograph A-90-C was employed. Chromatographic traces are presented of volatile fatty acid analyses with each of the liquid phases. Complete separation of all isomers of the fatty acids from C2 to C5 was accomplished by the Carbowax 20 M plus H3PO4, dioctyl sebacate plus sebacic acid, and dioctyl sebacate plus docosanoic acid columns. The latter two liquid phases were extremely unstable and proved to be unsatisfactory for analysis of aqueous samples. A column of Carbowax 20 M + H3PO4 separated steam-volatile organic acids completely. The volatile fatty acid isomers were separated by 5% Tween 80 somewhat less completely, and the peak shapes were not as sharp and symmetrical as that desired for good quantitative work. LAC-296 (20%) plus 2% H3PO4 proved to be the most satisfactory of the liquid phases for routine analysis of deproteinated in vitro rumen fermentation media. The column has been used for routine analysis of rumen fermentation fluid and in vitro rumen incubation fluid. All the organic acids from C2 to C5, except isobutyric, could be quantitated with this column. Stability of the column with the aqueous solutions was extremely good. The standard deviation of the analysis of each volatile acid component in a fermentation fluid was less than 0.5 molar per cent. The short-chain organic acids (C2 to C5) were shown to be extremely stable in aqueous solution for as long as 6 months after preparation for gas chromatographic analysis by protein precipitation with metaphosphoric acid-H2SO4 and refrigeration at 4 C in stoppered tubes.
... One cannot help but speculate on the acids that may not yet have come to light. Of interest in this respect is the paper of James and Martin (79) in which they report the detection in extracts of a culture of P. aeruginosa of a number of branched chain acids containing an odd number of carbon atoms ranging in length from C8 to C19. None of these acids was specifically identified, nor was it shown whether any of these compounds did, in fact, contain a cyclopropane ring. ...
... These volatile (C1-C,) and nonvolatile (lactic, fumaric, and succinic) acids have been analyzed by various gas-liquid chromatographic methods. Problems arising from direct chromatography of the volatile components include free acids interacting with metal columns and adsorbing to polar supports and stationary phases, resulting in poor quantitation due to sample loss, peak tailing, and ghosting (10,13). Moreover, many stationary phases have low thermal stabilities and tend to desorb ("bleed") from supports with repeated use. ...
Article
A method for the preparation and gas chromatographic analysis of the butyl esters of volatile (C1-C7) and nonvolatile (lactic, succinic, and fumaric) acids in microbial fermentation media is presented. Butyl esters were prepared from the dry salts of the acids. The esters were separated by temperature programming on a column of Chromosorb W coated with Dexsil 300 GC liquid phase and analyzed with a flame ionization detector. Apparent recoveries with butanol-HCl or butanol-H2SO4 as butylating agents were 80 to 90% for most acids. Chromatographic profiles of the butyl esters demonstrated that both volatile and nonvolatile acids can be detected and separated in 24 min on a single column. Standard calibration curves (peak area versus concentration) of the butyl esters were linear in the range of 5 to 40 μmol of acid per ml. The advantages of using an internal standard (heptanoic acid) for quantitating fatty acids in a mixture are given. Chromatograms of butylated fermentation media in which rumen anaerobic bacteria were grown illustrated that this method is useful for determining short-chain volatile and nonvolatile acids of taxonomic significance.
... A number of attempts to use various esters have been reported with limited success. Among these have been methyl (7)(8)(9)(10), ethyl (11), propyl (12), butyl (13)(14)(15), p-bromophenacyl (16), p-phenylphenacyl (16), and p-substituted benzyl esters (17). The use of anilide (18) and toluidine (19,20) derivatives has also been reported. ...
Volatile acids are recognized as useful indicators of decomposition in a variety of foods. A method has been developed for the rapid preparation of benzyl esters of formic, acetic, propionic, isobutyric, and butyric acids and for their quantitative determination by gas-liquid chromatography. Esters were formed by reaction with BCl3-benzyl alcohol, followed by washing with aqueous ammonia before storage. They were chromatographed, using tetradecane as an internal standard, and were separated at 140°C on columns having DC-200 and SP-1000 as liquid phases. The method offers significant advantages, especially for the determination of formic acid, over the present official AOAC method, 17.042-17.046. Recoveries of volatile acids added to steam distillates of tuna extracts were ≥ 91% with mean recoveries for the 5 volatile acids of 96—104%. Applications to the analysis of canned tuna, frozen headless shrimp, and frozen whole egg resulted in recoveries of ≥ 8 2% with mean recoveries for the 5 acids of 91—101%. The method was compatible with an automated gas chromatograph-data processing system.
Chapter
This chapter describes the identification of fatty acids by gas chromatography. The analysis of fatty acids by the method of gas chromatography is most advantageously carried out when these substances are present in the form of methyl esters. The methyl ester is very conveniently prepared and generally has a much lower boiling point than the free acid. It is observed that because it is also less polar and considerably less reactive, there is less likelihood of interaction with the stationary phase, the solid support, or the walls of the chromatographic column when metal tubing is used for either packed or capillary columns. The nonpolar liquid phase most widely employed for the analysis of fatty acid esters by gas chromatography is the high-vacuum stopcock grease. The most popular and effective polar materials are the adipate, glutarate, or succinate polyesters of ethylene or diethylene glycol. It is suggested that for the quantitative analysis of fatty acid esters by gas chromatography it is essential that the proportion of any stationary phase should not be reduced below 10%, the point where the absorptive properties of Celite 545 or Chromosorb-W are readily manifested.
Chapter
This chapter describes the techniques that are used for the separation and structural characterization of neutral glycerolipids having one to three molecules of fatty acid (esters) or alcohol (ethers) combined with the hydroxyl groups of glycerol. The emphasis is placed on practical considerations, and theoretical discussions are either brief or absent. Although references quoted in this chapter often do not indicate the original source of a procedure or idea, such information can be found within the comprehensive reviews that are cited in each section.
Chapter
The sections in this article are:1The Size, Structure and Function of the Adipose Organ2The Function of Adipose Tissue3Changing Concepts of Adiposity4Adiposity in Man
Chapter
The sections in this article are:
Chapter
Milk lipids have attracted the interest of and have frustrated investigators. The lipids are readily available, for example in butter, but are exceptionally complex, both with respect to lipid classes and to component fatty acids. Furthermore, the latter have been difficult to analyze because of the shortchain fatty acids present and the large number of fatty acids in general. Jenness and Patton (1959) listed 16 fatty acids found in milk lipids. The list had grown to about 150 by 1967 (Jensen et al. 1967) and is now over 400 (Table 4.1).
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An investigation of plasma lipid components in young adult rats of both sexes is reported. It was designed to find why part of the cholesterol-fed females given certain fats as 10% of adequate synthetic diets had a higher range of esterified plasma cholesterol values than males or than the rest of the females fed the same diets. Cottonseed and coconut oils were chosen as examples of unsaturated and saturated fats. Limitation of time of access to food resulted in shifting nearly all of the plasma cholesterol levels in cholesterol-fed females into the higher range. Increases in plasma cholesterol values in the restricted cholesterol-fed males were comparatively small. No significant correlation of high cholesterol levels with any phase of the estrus cycle was found. Data did not eliminate the possibility of differences in eating habits of ad libitum-fed females. Cholesterol feeding resulted, in rats of both sexes, in significant lowering of the percentage of arachidonic acid in plasma cholesterol ester. The change was greatest in the female rats with high cholesterol values and restricted access to food. When linoleic acid was available from the diet, it took the place of arachidonic acid in the cholesterol ester. Without it, i.e., when fed the coconut oil diet, the percentage of oleic acid was increased. There was a tendency toward maintenance of a relatively constant and characteristic ratio of unsaturated to saturated fatty acids in each of the plasma lipid fractions regardless of diet, sex or feeding pattern. Approximately 85% of the cholesterol ester fatty acids were unsaturated, those of triglycerides, 60 to 65%, of phospholipids about 55%. The data suggest that rate of esterification of excess dietary cholesterol may differ in males and females and that time restriction of access to food may delay removal of cholesterol ester from plasma to a greater extent in females than in males.
Article
Gas chromatography (GC) has been used for analysis of wine almost since its inception. While the focus of much research (both initially and currently) has been the application of GC for analysis of volatiles associated with aroma, many other analytes can be measured by GC, including pesticides, sugars, acids, amines, polyphenols, and organic metal-containing compounds (e.g. organic selenium). This review will discuss selected current applications of GC for analysis of wines, while emphasizing future trends and challenges.
Chapter
Gas chromatography (GC) has been used for the analysis of wine almost since its inception. While the focus of much research (both initially and currently) has been the application of GC for the analysis of volatiles associated with aroma, many other analytes can be measured by GC, including pesticides, sugars, acids, amines, polyphenols, and organic metal-containing compounds (e.g., organic selenium). This review will discuss selected current applications of GC for analysis of wines, while emphasizing future trends and challenges and providing an update since the first edition of this volume.
Article
Multiresidue methods are the most common approaches to analyze pesticide residues because the pesticide application on an agricultural commodity is usually not known. Since there are hundreds of pesticides available, it is essentially impractical to apply individual single residue analysis for every pesticide in various types of food products. The challenge is to process a sample using a single procedure or a limited number of procedures that can identify and quantitate as many pesticides with varying physical and chemical properties as possible that could potentially be present in a wide variety of agricultural matrices. Over the past 20 years, capillary gas chromatography-mass spectrometry (GC-MS) has played a major role in the analysis of pesticides in foods. Despite the increasing popularity of liquid chromatography-mass spectrometry (LC-MS), GC-MS is still widely used because of its affordability, ruggedness, and effectiveness in multiresidue pesticide procedures. GC-MS is primarily used to analyze a variety of thermally stable and volatile or semivolatile pesticides as well as other industrial contaminants such as PCBs, dioxins, brominated flame retardants, and related persistent organic pollutants in diverse food matrices that currently cannot be analyzed by conventional LC-MS methods. This chapter will attempt to account the past and present use and the future of multiresidue procedures that utilize a variety of GC-MS systems and platforms for the analysis of pesticide residues in foods and related agricultural products.
Chapter
Sowohl für den qualitativen Nachweis als auch für die quantitative Bestimmung chemischer Substanzen werden stets solche Methoden vorgezogen, die für die zu charakterisierende Substanz spezifisch sind.
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[3H8]Thromboxane B2 was biosynthesized and infused into an unanesthetized monkey. Several urinary metabolites were isolated and their structures elucidated using gas chromatography-mass spectrometry. In addition to the major urinary metabolite, dinor-thromboxane B2, a series of metabolites resulting from dehydrogenetion of the alcohol group at C-11 were identified: 11-dehydro-thromboxane B2, 11-dehydro-15-keto-13,14-dihydro-2,3-dinor-thromboxane B2, and 11-dehydro-15-keto-13,14-dihydro-19-carboxyl-2,3,4,5-tetranor-thromboxane B2. 6-(1,3-dihydroxypropyl)-7-hydroxy-10-oxo-3-pentadecaenoic acid was also identified. Three mono-O-ethylated metabolites were formed from thromboxane B2, which in this study was infused in an ethanolic solution. A small quantity of thromboxane B2 was excreted unchanged into the urine.
Trans isomers in several methyl ester mixtures and in some commercial margarines were separated on a 15′ × ⅛″ stainless steel column containing 10% Silar 10C as stationary phase. With the methyl ester mixtures, good agreement was obtained among known trans contents, trans contents determined by infrared (IR) spectroscopy, and trans contents determined by gas-liquid chromatography (GLC). With commercial margarines, agreement between IR and GLC results was less satisfactory; the latter were approximately 80–85% of the former when trans contents were >20%. When trans contents were <20%, discrepancies were larger. This was considered due to overlap of certain cis and trans positional isomers.
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Baobab seed oil contains specific fatty acids. Most of the studies on baobab fatty acids have been carried out singly and in isolation from each other, making it difficult to compare results through different species. The objective of the present study is to establish the seed fatty acid composition of each Adansonia species in order to evaluate and understand the relationships between the oil chemical compositions, the baobabs' taxonomy and, the ecological and geographical origin of each seed lot. The seed oils have been analysed using gas chromatography (GC). The oils of all baobab species contain three major fatty acids: palmitic, oleic and linoleic acids. They also contain specific fatty acids such as cyclopropenic and cyclopropanic acids, which are characteristic of the Malvaceae family seed oils. It was possible to distinguish three sections through principal components analysis using the 11 fatty acids identified by GC. The Adansonia section contains high rates of oleic acid (±35%), the Brevitubae section is rich in palmitic acid (±42%) and the Longitubae section contains high levels of dihydrosterculic acid (±5%). The oil fatty acid composition, however, does not enable a definitive characterization of profiles according to species. The fatty acid composition is not significantly influenced by the geographical, soil and climate conditions of the collection sites. This article is protected by copyright. All rights reserved.
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