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Trends in Purge and Trap
Abstract
Purge and trap is a widely recognized technique for the analysis of volatile organic compounds (VOCs) using gas chromatography
(GC). Improvements in the purge and trap method include techniques that attempt to make the preconcentration a transparent
part of the overall analysis. These techniques include methods and hardware capable of handling the wide array of sample matrices
encountered, minimizing matrix interferences inherent within the technique, and efficiently transferring the concentrated
sample to the GC for separation and subsequent detection. Present trends toward optimization of purge and trap include the
proper decision of concentration parameters, trapping adsorbents, GC inlet interfaces, and columns, each of which may be pivotal
for meeting specific application requirements/Strategies for run-time reduction, consistent with the trend toward smaller
bore capillary columns, have led to significant increases in productivity in the environmental analytical laboratory.
... This can enhance the detection of a wide range of VOCs by PT-GC-MS analysis. The parameters that affect PT efficiency and typically considered in PT optimization are purge gas flow rate, purge time, sample temperature and volume, desorption time and temperature, cold trap temperature, dry purge volume, ionic strength of the sample solution, and the type of trapping medium (Abeel et al. 1994;Driss and Bouguerra 1991;Kostiainen 1994;Ruiz-Bevia et al. 2009). Usually, GC-MS instrument parameters are also optimized to improve sensitivity. ...
... PT sampling devices directly interfaced to GC-MS are commercially available. In fact, the design of PT concentrators have undergone pertinent improvements notably through the integration of foam filters and efficient trap water removal systems (Abeel et al. 1994). These enhancements have effectively mitigated the operational challenges that were prevalent during the initial widespread adoption of PT concentrators in the 1980s (Abeel et al. 1994;Rose and Colby 1979 Furthermore, the PT technique is also utilized in methods for characterizing naturally-occurring elemental and organometallic species (Amouroux et al. 1998;Hardisty et al. 2020;Yang et al. 2022). ...
... In fact, the design of PT concentrators have undergone pertinent improvements notably through the integration of foam filters and efficient trap water removal systems (Abeel et al. 1994). These enhancements have effectively mitigated the operational challenges that were prevalent during the initial widespread adoption of PT concentrators in the 1980s (Abeel et al. 1994;Rose and Colby 1979 Furthermore, the PT technique is also utilized in methods for characterizing naturally-occurring elemental and organometallic species (Amouroux et al. 1998;Hardisty et al. 2020;Yang et al. 2022). Such species are found at very low concentrations, ranging from nmol L −1 to fmol L −1 , in biological and environmental matrices (Amouroux et al. 1998). ...
This review delves into the efficacy of utilizing bubbles to extract analytes into the gas phase, offering a faster and greener alternative to traditional sample preparation methods for mass spectrometry. Generating numerous bubbles in liquids rapidly transfers volatile and surface‐active species to the gas phase. Recently, effervescence has found application in chemical laboratories for swiftly extracting volatile organic compounds, facilitating instantaneous analysis. In the so‐called fizzy extraction, liquid matrices are pressurized with gas and then subjected to sudden decompression to induce effervescence. Alternatively, specifically designed effervescent tablets are introduced into the liquid samples. In situ bubble generation has also enhanced dispersion of extractant in microextraction techniques. Furthermore, droplets from bursting bubbles are collected to analyze non‐volatile species. Various methods exist to induce bubbling for sample preparation. The polydispersity of generated bubbles and the limited control of bubble size pose critical challenges in the stability of the bubble–liquid interface and the ability to quantify analytes using bubble‐based sample preparation techniques. This review covers different bubble‐assisted sample preparation methods and gives practical guidance on their implementation in mass spectrometry workflows. Traditional, offline, and online approaches for sample preparation relying on bubbles are discussed. Unconventional bubbling techniques for sample preparation are also covered.
... Reportedly, sample preparation, separation, and spectroscopic techniques are the main phases of foodomics [5]. In sample preparation techniques, a small amount of food can be prepared for more complicated arrays of analysis [13]. This technique has advantages like increasing selectivity, saving time, reducing environmental damages, reducing the costs, etc. ...
... This technique has advantages like increasing selectivity, saving time, reducing environmental damages, reducing the costs, etc. For instance, to have a better proteomics study, a high-yield protein and peptide substances should be prepared from the smaller amount of food for further analysis [13]. Additionally, to have a high-efficacy purge and trap method, the high-concentration and enrich volatile organic compounds should be separated [11]. ...
Human nutrition is a multifaceted, complex, and broad scientific field, demonstrating how food components, ingredients and
flavors present required nourishment for the life-sustaining.
Since the dawn of civilization, food and nutrition components have
been obligated to maintain human life by releasing energy.
However, over the decades, human nutrition has been widely considered as a promising resource to treat and/or prevent diseases. Recently, the application of modern research in nutrition
and food science has been shifted from classical technologies and
equipment to advance analytical methodologies. To achieve the
the mentioned goal, a new discipline, namely called foodomics, was
introduced as the global strategy by using the application of
advanced omics in the food science domain.
... The purge and trap technique is a solvent-less extraction method with a high extraction efficiency though it was first developed for water and soil concentration of analytes [59]. The purge and trap technique was compared with simultaneous distillation extraction to analyze volatiles from Citrus sudachi [53]. ...
Compounds useful for drugs, cosmetics, and food have been obtained directly or indirectly from living organisms over the years. However, there has been a renewed interest in getting useful compounds from living organisms, especially plants. Essential oils, interchangeably called volatile oils, are bioactive compounds found in minute quantities in some plants. Essential or volatile oils have been known for years to find usefulness in foods, drugs (antimicrobial, antifungal), and cosmetics. This review attempts to summarize information on the essential oil from Ficus species concerning their morphology, pharmacology, bioactivity, and application. This was achieved by gathering information on essential oils from different Ficus species. Essential oils from Ficus species are a good source of bioactive compounds for use in drug, food, and cosmetic industries. It is worthy to note that Nigerian Figs were characterized by the high presence of phytol and 6,10,14-trimethyl-2-pentadecanone, and these compounds are, therefore, seen as markers. Furthermore, this review presents numerous insights on how to best harness the different potentials of the essential oils and possibilities to be examined.
... Those compounds are widely distributed in natural gas, crude oils, source rocks, sediments, oilfield water, and other types of reservoir fluids. Besides, their δ 13 C ratios contain abundant geochemical information and are considered as an effective proxy associated with oilgas formation and evolution [18,19]. However, it is difficult to analyze them directly by CSIA features with GC/IRMS, for those hydrocarbons are always beyond the detection limit of the instrument or very easy to escape during the preparation process [20]. ...
Sample preparation technique, for the analysis of δ¹³ C ratios in oil and gas samples, has gradually been recognized as one of the most crucial steps of the whole analytical process. In this study, a new convenient method, syringe solid phase extraction (SSPE), was proposed for measuring δ¹³ C in natural gas samples. Based on conditional experiments of temperature and time, SSPE fitted with activated carbon adsorbent was applied with a gas chromatography/isotope ratio mass spectrometry (GC/IRMS) system for trace carbon isotope analysis. The results showed that isotopic fractionation was not clearly observed during the adsorption and desorption process, and the δ¹³ C ratios measured by SSPE-GC/IRMS were in good agreement with the known δ¹³ C ratios of CH 4 ~C 5 H 12 measured by GC/IRMS with the accuracy all within ±0.48‰. A natural gas sample was applied to verify the efficiency of this new method, and the obtained results confirmed that SSPE-GC/IRMS is a reliable technique characterized with simplicity, efficiency, and reliability.
... However, the use of relatively long sample column and large sample volumes are critical to achieve satisfactory extraction efficiencies. To boost analytical performance, the effluent gas extracts are often trapped prior to analysis, as it is in purge-closed-loop and purge-and-trap methods (Wang & Lenahan, 1984;Abeel, Vickers & Decker, 1994). In general, the gas stripping approach-relying on concentration of the liberated analytes into small volumes-is time-consuming, requires the supply of energy (electricity for heating) and additional consumable materials (sorbent, cryogenic agent). ...
Fizzy extraction (FE) facilitates analysis of volatile solutes by promoting their transfer from the liquid to the gas phase. A carrier gas is dissolved in the sample under moderate pressure (Δ p ≈ 150 kPa), followed by an abrupt decompression, what leads to effervescence. The released gaseous analytes are directed to an on-line detector due to a small pressure difference. FE is advantageous in chemical analysis because the volatile species are released in a short time interval, allowing for pulsed injection, and leading to high signal-to-noise ratios. To shed light on the mechanism of FE, we have investigated various factors that could potentially contribute to the extraction efficiency, including: instrument-related factors, method-related factors, sample-related factors, and analyte-related factors. In particular, we have evaluated the properties of volatile solutes, which make them amenable to FE. The results suggest that the organic solutes may diffuse to the bubble lumen, especially in the presence of salt. The high signal intensities in FE coupled with mass spectrometry are partly due to the high sample introduction rate (upon decompression) to a mass-sensitive detector. However, the analytes with different properties (molecular weight, polarity) reveal distinct temporal profiles, pointing to the effect of bubble exposure to the sample matrix. A sufficient extraction time (~12 s) is required to extract less volatile solutes. The results presented in this report can help analysts to predict the occurrence of matrix effects when analyzing real samples. They also provide a basis for increasing extraction efficiency to detect low-abundance analytes.
... Definitely the highest similarity and intensity scores were given to those extracts gained by 60°C, 45°C, and after 30°C because most of the compounds that basil possess the high boiling points (Lawrence, 1988). Nonetheless, the higher temperature resulted in better representativeness, and to avoid artifacts formation the maximum temperature was settled to 60°C (Abeel et al., 1994). As observed in both figures, the extraction time affected the representativeness and generally increased the score. ...
Volatile profile, aroma-active compounds and odor activity values of the shade-dried aerial parts of basil (Ocimum basilicum) were investigated. Basil samples used under the study were provided from Iran and Turkey. Volatile compounds were isolated using a purge and trap extraction system and analyzed by gas chromatography olfactometry. A total of 50 volatile compounds of which 29 originated from Iranian and 32 were of Turkish origin were determined. Terpenes were present at the overwhelmingly highest levels, followed by alcohols and aldehydes. Of the terpenes, methyl chavicol was the main compound of both samples. The aroma-active compounds of basils were investigated by using aroma extract dilution analysis (AEDA) for the first time. The application of AEDA revealed 18 aroma-active compounds, including terpenes (10), aldehydes (3), ketone (1), phenol (1), alcohol (1), and unknown compounds (2) were detected. Linalool and methyl chavicol had the greatest flavour dilution (FD) factors in both samples, amounting to 2048 and 1024, respectively.
... Definitely the highest similarity and intensity scores were given to those extracts gained by 60°C, 45°C, and after 30°C because most of the compounds that basil possess the high boiling points (Lawrence, 1988). Nonetheless, the higher temperature resulted in better representativeness, and to avoid artifacts formation the maximum temperature was settled to 60°C (Abeel et al., 1994). As observed in both figures, the extraction time affected the representativeness and generally increased the score. ...
Volatile profile, aroma-active compounds and odor activity values of the shade-dried aerial parts of basil (Ocimum basilicum) were investigated. Basil samples used under the study were provided from Iran and Turkey. Volatile compounds were isolated using a purge and trap extraction system and analyzed by gas chromatography olfactometry. A total of 50 volatile compounds of which 29 originated from Iranian and 32 were of Turkish origin were determined. Terpenes were present at the overwhelmingly highest levels, followed by alcohols and aldehydes. Of the terpenes, methyl chavicol was the main compound of both samples. The aroma-active compounds of basils were investigated by using aroma extract dilution analysis (AEDA) for the first time. The application of AEDA revealed 18 aroma-active compounds, including terpenes (10), aldehydes (3), ketone (1), phenol (1), alcohol (1), and unknown compounds (2) were detected. Linalool and methyl chavicol had the greatest flavour dilution (FD) factors in both samples, amounting to 2048 and 1024, respectively.
Fizzy extraction (FE) is a technique that utilizes effervescence phenomenon to extract volatile organic compounds (VOCs) from liquid matrices for subsequent analysis. To induce effervescence, a liquid sample is first pressurized (at ∼ 150 kPa) with an extractant gas (here, nitrogen), and then rapidly depressurized. In this work, we combine an in-house-built FE system with a commercial ion-mobility spectrometry (IMS) module in order to develop a portable analytical platform for in situ analysis of VOCs in liquid samples. The size and shape of the FE-IMS platform are similar to those of a typical airline catering trolley. Its operation is enabled by several electronic and electromechanical components (a single-board computer, two microcontroller boards, a relay board, six DC-DC converters, a pressure regulator, a solenoid valve, and a pinch valve). The platform can carry out the extraction procedure as well as acquire, process, and transmit the data to a cloud-storage service. A custom-designed graphical user interface allows the user to select one of the available operation modes: full spectrum mode, ion current profile mode, and cleaning mode. The interface also allows one to follow the analysis progress, display the final result, and upload it to the Internet cloud. The platform has been characterized using three standards: ethyl acetate, ethyl propanoate, and butanone; and their limits of detection are 4.51 × 10⁻⁸ M, 2.74 × 10⁻⁸ M, and 1.26 × 10⁻⁷ M, respectively. Furthermore, its ability to analyze real samples (alcoholic and non-alcoholic beverages) has been demonstrated.
Covering: up to 2019
Soon after the birth of gas chromatography, mass spectrometry and olfactometry were used as detectors, which allowed impressive development to be achieved in the area of odorant determinations. Since the mid-80s, structured methods of gas chromatography-olfactometry have appeared, allowing the determination of which odor constituents play a key role in materials. Progressively, numerous strategies have been proposed for sample preparation from raw materials, the representativeness evaluation of extracts, the identification of odor constituents, their quantification, and subsequently, the recombination of the key odorants to mimic the initial odor. However, the multiplicity of options at each stage of the analysis leads to a confusing landscape in this field, and thus, the present review aims at critically presenting the available options. For each step, the most frequently used alternatives are described, together with their strengths and weaknesses based on theoretical and experimental justifications according to the literature. These techniques are exemplified by many applications in the literature on aromas, fragrances and essential oils, with the initial focus on wine odorants, followed by a short overview on the molecular diversity of key odorants, which illustrates most of the facets and complexities of odor studies, including the issues raised by odorant interactions such as synergies.
A vast number of organic micropollutants has been detected in the aqueous environment. A number of these compounds can eventually occur in our drinking water. The growing awareness of the risks associated with the occurrence of pollutants in drinking water led to the development of a diversity of sophisticated analytical methods. The basis of the major part of the currently used methodology is chromatography. Hyphenation of spectroscopic and chromatographic techniques is one of the most important trends in chromatography today. On the other end immunochemical techniques are emerging both as screening techniques and in combination with chromatography. This chapter gives an overview of the state-of-the-art in the analysis of the most important groups of pollutants in drinking water.
Method 524.2, Revision 3.0, is a laboratory analytical method for the determination of 59 volatile organic compounds (VOCs)
in water. The method uses purge-and-trap techniques to isolate VOCs from a water matrix, and capillary column gas chromatography—mass
spectrometry (GC/MS) for the identification and measurement of the analytes. This study evaluated 48 additional compounds
of environmental interest as candidates for possible inclusion in the method. The new candidate VOCs include many polar, water
soluble compounds that are very difficult to remove from the water matrix. The initial evaluation tested the candidate VOCs
in fortified reagent water for sensitivity and linearity of response. Results indicated that 28 of the compounds had sufficient
potential to warrant further study. Additional studies investigated purging efficiency, precision and accuracy, method detection
limits (MDLs), sample preservation and storage, and possible matrix effects. Final results demonstrated that Method 524.2,
Revision 3.0, was capable of determining 24 of the candidate VOCs with acceptable accuracy and precision. MDLs were generally
1 μg/L or lower.
Presented here is a method for quantitative recovery of volatile organic compounds followed by a description of apparatus and procedures employed to detect 0.5 μg/l of the substances.
A method has been developed for trapping and preconcentrating the very volatile replacement chlorofluorocarbons (hydrofluorocarbons and hydrochlorofluorocarbons) using microtraps filled with Carboxen, a carbon molecular sieve type material, without the need for extensive cryotrapping using liquid nitrogen. We present here the adsorption characteristics of four Carboxen materials, Carboxen 569, 1000, 1001, and 1002, used to trap a range of replacement chlorofluorocarbons varying in boiling point from −48.4 to −9.8°C. The application of these traps for the automated analysis of trace gases in atmospheric and environmental chemistry could prove extremely useful.
A method is described for the determination of volatile organic compounds in water. It involves the direct purging of a sample to a fused silica capillary column. As they are purged, the compounds are focused on a DB-624 column (0.32- or 0.53-mm i.d.) with whole column cryotrapping (WCC). WCC at -90 to -80°C traps all of the purgeable priority pollutant compounds. After purging, the gas chromatography run is started immediately. This purge and whole column cryotapping (P/WCC) method is facilitated by the fact that water is relatively nonvolatile; at 20°C, the equivalent of only 0.9 μL of liquid water is transported to the column for every 50 mL of purge gas at the purge vessel pressure. Advantages of P/WCC include (1) simplicity and therefore high reliability, (2) low background contamination since no sorbent traps or multiport valves are needed, (3) no need to retain very volatile compounds on an intermediate trap as in purge and trap, and (4) very short run times.
Volatile organics are often separated from water samples by bubbling an inert gas through the water and collecting the organics on a sorbent trap, a technique known as purge and trap. Unfortunately, during the analysis of many water samples, foam can climb through the apparatus and contaminate the trap. This research project has investigated both chemical and mechanical antifoaming techniques. A total of 27 potential chemical antifoaming agents were evaluated for their ability to control foam. Two silicone-based commercial antifoam emulsions, Dow Corning Antifoam C and General Electric AF-72, were rated superior overall. The final protocol specifies use of 2 drops of purified silicone antifoam emulsion (General Electric AF-72) in a 5.0-mL sample which is purged in a 60-mL purge flask. The procedure was validated with seven volatile compounds (29-159 ng) spiked into four wastewaters. Mean recovery (vs. purge of distilled water) was 97%.
The kinetics of organics purging in the purge-and-trap gas chromatography/mass spectrometry technique for the concentration of volatile compounds in water using primary fragment ions in modified method 524.2 is revealed to be first order with respect to purging time. This kinetic model is applicable from a concentration of 200 ppb for ketones and nitrogen compounds to the sub-ppb levels for more readily purgeable volatile compounds. The purging ratios of the compounds, as well as their first-order purging rate constants, are obtained. The rate constant can be used as an alternative guide to gas chromatographic retention time for the selection of internal standards for quantitation purposes and/or replacement of surrogates for performance and quality assurance.
Underwater hydrocarbon vent and formation water samples, two discharges from offshore production operations in the Gulf of Mexico, were compositionally characterized for volatile liquid hydrocarbons (VLHs). Hydrocarbons in surface samples of an underwater vent were not detected with carbon numbers greater than 10 (n-C10). Alkanes were the major components of all of the VLHs in vent samples with less than 10% being aromatic hydrocarbons. Hydrocarbons in samples of a formation water discharge were considerably more extensive and complex than vented hydrocarbons. Total VLH concentrations were ~20 mg/L, 80% of which were aromatic hydrocarbons ( mostly benzene, toluene, and xylenes), close to the percentage found in coastal waters of the Gulf of Mexico. Considerable amounts of C3 and C4 alkylbenzenes (100-400 μg/L per component) were evident. Estimations of the amount of VLH discharged into the outer continental shelf of Louisiana and upper Texas from these two discharges were made for underwater hydrocarbon venting, 400 x 106-1200 x 106 g/yr, and for formation waters, 750 x 106-1100 x 106 g/yr.