Carboxen/polydimethylsiloxane Research Articles

Volatile compounds of Croatian cheese in a lamb skin sack prepared from a mixture of goat's and cow's milk

Volatile aroma compounds are one of the main parameters in consumer choice and acceptance of cheese. The traditional way of making cheese, still preserved in Croatia, is the anaerobic ripening of curds in a lamb or goat sack. Cheeses produced in such a way have a specific aroma. The objective of this study was to determine the volatile compounds of Croatian cheese in a lamb skin sack prepared from a mixture of goat's and cow's milk and relate them with the aroma of this traditional cheese. The cheese extracts were obtained by headspace solid-phase microextraction (HS-SPME) and ultrasonic solvent extraction (USE) and analysed by gas chromatography-mass spectrometry (GCMS). HS-SPME was performed at different temperatures (40, 50 and 60°C) using 2 fibres, divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre and carboxen/ polydimethylsiloxane (CAR/PDMS) fibre. Increasing the extraction temperature resulted in higher sorption of fatty acids on both fibres. A total of 28 volatile compounds were identified in the cheese samples including 13 acids, 10 esters, 2 alcohols, 2 hydrocarbons and 1 ketone. Results revealed that fatty acids were the predominant group of volatile compounds in all samples. In samples obtained by HS-SPME, the most abundant were hexanoic, octanoic, butanoic, acetic and decanoic acid while (Z)-octadec-9-enoic, hexadecanoic, decanoic and tetradecanoic acid were the most abundant in the sample obtained by USE.

Simple and accurate on-site quantitation of BTEX in atmospheric air using solid-phase microextraction and gas chromatography with photoionization detection

This paper represents an improved method for on-site quantitation of benzene, toluene, ethylbenzene, and xylenes (BTEX) in atmospheric air using solid-phase microextraction (SPME) and portable gas chromatography with a split/splitless inlet and photoionization detector (GC-PID). The developed method includes air pumping to four replicate 250 mL gas sampling bulbs, three of which are extracted by 85 µm Carboxen/polydimethylsiloxane (Car/PDMS) coating at 40°C, while the last one is spiked with BTEX standard in nitrogen and extracted under the same conditions. Compared to other similar SPME-based methods, the developed method does not require a standard gas generator and traceable certified permeation tubes for instrument calibration.The method was applied for on-site BTEX quantitation in air of Talgar, Almaty oblast, Kazakhstan in February and March 2024, at two different extraction times, among which 15 min was chosen as optimal because it provided sufficient detection limits of ethylbenzene, and xylenes. The on-site standard addition calibration allowed accurate BTEX quantitation. In February, only benzene (18.3 and 6.8 µg/m3) and toluene (15.7 and 8.5 µg/m3) were detected. In March samples, concentrations of benzene were 12.3 and 7.4 µg/m3, toluene - 23 and 5.4 µg/m3, ethylbenzene – 5.5 µg/m3 and not detected, m-/p-xylene - 3.6 and 2.1 µg/m3, o-xylene - 6.8 and 10.6 µg/m3. The LODs for benzene, toluene, ethylbenzene, m-/p-xylene, and o-xylene were 0.07, 0.3, 2, 0.8 and 2 µg/m3, respectively. The developed method can be recommended for quick and low-cost on-site quantification of BTEX in atmospheric air, particularly at remote locations.

Enhancement of Benzene Emissions in Special Combinations of Electronic Nicotine Delivery System Liquid Mixtures.

Electronic nicotine delivery systems (ENDS) are battery-powered devices introduced to the market as safer alternatives to combustible cigarettes. Upon heating the electronic liquid (e-liquid), aerosols are released, including several toxicants, such as volatile organic compounds (VOCs). Benzene has been given great attention as a major component of the VOCs group as it increases cancer risk upon inhalation. In this study, several basic e-liquids were tested for benzene emissions. The Aerosol Lab Vaping Instrument was used to generate aerosols from ENDS composed of different e-liquid combinations: vegetable glycerin (VG), propylene glycol (PG), nicotine (nic), and benzoic acid (BA). The tested mixtures included PG, PG + nic + BA, VG, VG + nic + BA, 30/70 PG/VG, and 30/70 PG/VG + nic + BA. A carboxen polydimethylsiloxane fiber for a solid-phase microextraction was placed in a gas cell to trap benzene emitted from a Sub-Ohm Minibox C device. Benzene was adsorbed on the fiber during the puffing process and for an extra 15 min until it reached equilibrium, and then it was determined using gas chromatography-mass spectrometry. Benzene was quantified in VG but not in PG or the 30/70 PG/VG mixtures. However, benzene concentration increased in all tested mixtures upon the addition of nicotine benzoate salt. Interestingly, benzene was emitted at the highest concentration when BA was added to PG. However, lower concentrations were found in the 30/70 PG/VG and VG mixtures with BA. Both VG and BA are sources of benzene. Enhanced emissions, however, are mostly noticeable when BA is mixed with PG and not VG.

COMPARISON OF DIFFERENT SOLID PHASE MICROEXTRACTION FIBERS IN EXTRACTION OF VOLATILE COMPOUNDS FROM ADIPOSE TISSUE

The volatile compounds (VCs) in headspace of adipose tissues (perirenal, tail, caul) were extracted by solid-phase microextraction (SPME) fiber coated with carboxen/ polydimethylsiloxane (CAR/PDMS) or divinylbenzene/ carboxen/ polydimethylsloxane (DVB/CAR/PDMS). In extraction with CAR/PDMS coating compared to DVB/CAR/PDMS, more VCs were obtained in perirenal (53 versus 41), tail (51 vs 47) and caul (35 vs 33) fats. Increased retention index for aldehydes increased the adsorption on DVB/CAR/PDMS. This fiber also provided a good yield for carboxylic acids. CAR/PDMS fiber could be recommended for VCs from adipose tissues if the goal is to identify aldehydes, especially fatty acid oxidation products and low molecular weight hydrocarbons, as well as greater number of VCs. However, in case of targeting carboxylic acids, esters, and also high molecular weight aldehydes, DVB/CAR/PDMS could be utilized due to its high affinity for mentioned compounds. Furthermore, the optimum extraction time should be studied to determine the time for VCs to reach equilibrium.

Comparison of four commercial solid-phase micro-extraction (SPME) fibres for the headspace characterisation and profiling of gunshot exhausts in spent cartridge casings

Headspace solid-phase micro-extraction (SPME) is a promising technique for the characterisation and profiling of gunshot exhausts in spent cartridge casings, especially for health and environmental risk assessments, as well as forensic purposes. To date, however, no comprehensive investigation has been carried out to objectively assess the kinds of compound released during a discharge that can be recovered by this approach, the selectivity of the main commercially available fibres, and their relative performances for the analysis of gunshot exhausts and the discrimination of different ammunition types. This study aimed to fill this gap. Gunshot exhausts in spent cartridge casings from four different ammunition types were analysed by GC–MS, after extraction with four different commercial fibres: 100 μm polydimethylsiloxane (PDMS), 85 μm polyacrylate (PA), 65 μm polydimethylsiloxane/divinylbenzene (DVB), and 85 μm carboxen/polydimethylsiloxane (CAR). Results showed that, overall, a total of 120 analytes could be observed across the cartridges, but the different tested fibres also displayed distinct performances, which were, to some extent, complementary for the characterisation of gunshot exhausts. DVB, in particular, recovered the most compounds simultaneously. On the other hand, the observed variability between measurements was also high, making it a poor candidate for (semi-)quantitative applications (e.g. estimation of time since discharge and/or source profiling). In this regard, PA demonstrated the highest potential for broad use and implementation in multi-purpose methods.

Quantification of trace transformation products of rocket fuel unsymmetrical dimethylhydrazine in sand using vacuum-assisted headspace solid-phase microextraction.

Quantification of unsymmetrical dimethylhydrazine transformation products in solid samples is an important stage in monitoring of environmental pollution caused by heavy rockets launches. The new method for simultaneous quantification of unsymmetrical dimethylhydrazine transformation products in sand samples using vacuum-assisted headspace solid-phase microextraction without addition of water followed by gas chromatography-mass spectrometry is proposed. Decreasing air evacuation time from 120 to 20 s at 23 °C resulted in increased responses of analytes by 25-46% and allowed obtaining similar responses as after evacuation at -30 °C. The best combination of responses of analytes and their relative standard deviations (RSDs) was achieved after air evacuation of a sample (m = 1.00 g) for 20 s at 23 °C, incubation for 30 min at 40 °C, and 30-min extraction at 40 °C by Carboxen/polydimethylsiloxane(Car/PDMS) fiber. The method was validated in terms of linearity (R2=0.9912-0.9938), limits of detection (0.035 to 3.6 ng g-1), limits of quantification (0.12-12 ng g-1), recovery (84-97% with RSDs 1-11%), repeatability (RSDs 3-9%), and reproducibility (RSDs 7-11%). It has a number of major advantages over existing methods based on headspace solid-phase microextraction-lower detection limits, better accuracy and precision at similar or lower cost of sample preparation. The developed method was successfully applied for studying losses of analytes from open vials with model sand spiked with unsymmetrical dimethylhydrazine transformation products. It can be recommended for analysis of trace concentrations of unsymmetrical dimethylhydrazine transformation products when studying their transformation, migration and distribution in contaminated sand.

Chitosan and dicationic ionic liquid intercalated clay-coated solid-phase microextraction fiber for determination of sixteen polycyclic aromatic hydrocarbons in coffee and tea samples

In the present study, solid-phase microextraction (SPME) fiber was prepared by coating clay (MMT)-chitosan (CH) and dicationic ionic liquid (DIL) onto the stainless-steel wire step by step. The characterization of fibers was performed by Fourier transform infrared spectroscopy, thermal analysis, x-ray diffraction analysis, and scanning electron microscopy. The prepared fibers were evaluated for separation and determination of 16 polycyclic aromatic hydrocarbons (PAHs) in coffee and tea samples in headspace- and direct immersion-SPME by coupling with gas chromatography/mass spectrometry. The analytical performance of MMT/CH/DIL fibers was carried out for the extraction of PAHs and compared with the performance of carboxen/polydimethylsiloxane (CAR/PDMS) and divinylbenzene/CAR/PDMS (DVB/CAR/PDMS) fibers under optimized conditions. The wider linear ranges between 0.001 and 25 μg L−1 with a coefficient of determination above 0.9962, low limits of detection between 0.0001 and 0.05 μg L−1 and good intra-day repeatability from 2.45 to 6.48 % and fiber-to-fiber reproducibility from 3.19 % to 8.82 % were obtained for all PAHs in both methods with MMT/CH/octyl (O)-DIL fiber. The extraction recoveries of coffee and tea samples ranged from 87.5 to 112 % using the MMT/CH/O-DIL fiber in both SPME methods.

Development of porous carbon/polydimethylsiloxane thin-film solid-phase microextraction membranes to facilitate on-site sampling of volatile organic compounds

This work presents the development of carboxen/polydimethylsiloxane (Car/PDMS) based thin film-solid phase microextraction (TF-SPME) method capable of identifying volatile organic compounds (VOCs) in hot-tub-air and human-breath samples. The proposed TF-SPME membranes were developed using carbon mesh sheets loaded with Car/PDMS and nanocarbon/polydimethylsiloxane (NCar/PDMS) sorbents consistent with sustainable chemistry principles. The membrane surfaces were examined using a stereo microscope system and were evaluated based on the effect of various particle ratios (1%, 2.5%, 5%, 10%, and 15%). The results showed that membranes with higher particle ratios provided a higher extraction efficiency when used with McReynolds standards; however, membranes containing 10% and 15% carbon were fragile and suffered from substantially higher background bleed. Hence, a sorbent with a 5% particle ratio was deemed to be optimal, and the carboxen coating was found to capture the highest amounts of the McReynolds standard. Moreover, Car/PDMS and NCar/PDMS were found to provide good repeatability, as their intra-membrane %RSDs fell within an acceptable range—1.2%–21.9% and 1.7%–20%, respectively—for all analytes tested. Finally, for proof-of-concept applications, the developed membranes were used to sample chlorination by-products (chloroform and dichloroacetonitrile) from hot tub headspace and were identified using a hand portable gas chromatography-mass spectrometry (GC-MS) system. In second application 33 VOCs in human-breath samples sampled and identified using a benchtop GC-MS system.

In vivo and in vitro Volatile Constituents of the Flowers of Xylopia aromatica by HS‑SPME/GC-MS

Xylopia aromatica (Lam.) Mart. (Annonaceae) is a typical species from the Brazilian cerrado that presents medicinal properties. The plant is distinguished by its large white flowers which produce a pleasant fragrance. X. aromatica is characterized by a wide range of medicinal application. These characteristics have motivated us to investigate the flowers volatile organic compounds (VOCs) via in vivo and in vitro protocols by a headspace solid-phase microextraction (HS‑SPME) technique combined with gas chromatography-mass spectrometry (HS-SPME/GC‑MS). Four different fibers, extraction times and temperatures were the parameters changed to lead to the maximum profiling of the volatile constituents. Data were analyzed using principal component analysis (PCA). A total of 77 VOCs were extracted from the floral scent, with 52 and 68 extracted from in vivo and in vitro sampling, respectively, of which 48 were reported for the first time in the literature as volatile constituents from X. aromatica flowers. The extraction and identification of VOCs were successfully performed through HS-SPME/GC-MS. The PCA data allowed the identification of parameters that led to the maximum number of VOCs, which were polyacrylate (PA) and carboxen/polydimethylsiloxane (CAR/PDMS) fibers, 60 min extraction time and temperature of 29.0 °C. Among the volatile constituents identified, sesquiterpenes predominated, comprising about 61.04%.

Effect of cocoa roasting time on volatile composition of dark chocolates from different origins determined by HS-SPME/GC-MS

ABSTRACT In this study the volatile composition of six samples of dark chocolates varying in the cocoa roasting time (30.5, 34.5 and 38.5 min) and geographical origin (Ecuador and Ghana) was characterized by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). One hundred and twenty-one different compounds were identified using a carboxen/polydimethylsiloxane (CAR-PDMS) fiber comprising acids, alcohols, aldehydes, alkanes, esters, furans, ketones, nitrogen compounds, pyran derivatives, pyrazines, pyrroles and thiazoles. The effect of roasting time on the volatile composition of chocolates depended on their geographical origin. Principal component analysis (PCA) was applied to volatile composition of the six dark chocolate samples. Eight different groups of compounds were established according to the position of the aroma compounds on the PC plot and accordingly to variation among samples. Therefore, volatile compounds that appeared or disappeared during roasting of cocoa from each origin or both origins were identified.

Method for characterization of volatile organic compounds in the diet of Centris analis (Hymenoptera, Apidae, Centridini) immatures

This study tested three types of Solid-Phase Microextraction fibers in developing a method to extract volatile organic compounds present in the diet of immature Centris analis. Samples were placed in glass vials with metal lids and added with 3g NaCl and 8 ml deionized water. Extraction and characterization were carried out using a Headspace – Solid Phase Microextraction (HS-SPME) with Gas Chromatography – Mass Spectrometry, and the three types of fibers were polydimethylsiloxane (PDMS), divinylbenzene/ carboxen/ polydimethylsiloxane (DVB/CAR/PDMS) and carboxen/ polydimethylsiloxane (CAR/PDMS). Each type of fiber was exposed to volatiles for 30 min and analyzed in a chromatograph Agilent GC-MS equipped with a quadrupole detector (MSD 5977A), containing a HP-5MS (30 m x 0.25 mm x 0.25 µm) column and Helium as the carrier gas (1 ml.min-1). The CAR / PDMS fiber favored the extraction of volatile compounds to semi-volatile compounds, followed by DVB / CAR / PDMS, while PDMS presented a lower number of extracted compounds, which can be attributed to its apolar nature. The volatile compounds identified in the diet included alcohols, aldehydes, esters, ketones, and terpenes. The SPME technique has proven effective in the extraction of volatile organic compounds from immature of Centris analis diet, being the CAR/PDMS the most suitable fiber for this.

OPTIMIZATION OF EXTRACTION CONDITIONS OF VOLATILE COMPOUNDS OF ROASTED BEEF BY SOLID-PHASE MICROEXTRACTION

Aroma is one of the most important sensory attributes for acceptance by beef consumers. The first step in analysing the volatile compounds associated with this attribute is their extraction from the food matrix, solid-phase microextraction has been widely used for volatile compound determination in meat. This study aimed to test six different solid-phase microextraction (SPME) fibre coating materials for their volatile compounds extraction efficiency for roasted beef and to optimize the extraction conditions using response surface methodology. Gas chromatography coupled with a flame ionization detector (GC-FID) and mass spectrometry (GC-MS) were used. The choice of SPME fibre coating was based in the total area obtained by GC-FID analysis for the six fibre coatings. The optimum time and temperature for SPME extraction was 60 °C/65 minutes. The mixed-phase fibre coatings showed the best results for extracting volatile compounds in roasted beef as higher number of compounds were identified. The carboxen/polydimethylsiloxane (CAR/PDMS) fibre extracted the largest number of compounds under the optimum extraction condition. Aldehydes were the predominant class of compounds found in roasted beef, followed by alcohols and hydrocarbons.

Modeling solid-phase microextraction of volatile organic compounds by porous coatings using finite element analysis

Experimental optimization of analytical methods based on solid-phase microextraction (SPME) is a complex and labor-intensive process associated with uncertainties. Using the theoretical basics of SPME and finite element analysis software for the optimization proved to be an efficient alternative. In this study, an improved finite element analysis-based model for SPME of volatile organic compounds (VOCs) by porous coatings was developed mainly focussing on the mass transport in coatings. Benzene and the Carboxen/polydimethylsiloxane (Car/PDMS) coating were used as the model VOC and a porous SPME coating, respectively. It has been established that in the coating, volumetric fractions of Carboxen, PDMS, and air are 33, 42 and 24%, respectively. Knudsen diffusion in micropores can slow down a mass transport of analytes in the coating. When PDMS was considered as the solid part of the coating, lower root-mean-square deviation of the modeling results from experimental data was observed. It has been shown that the developed model can be used to model the extraction of VOCs from air and water samples encountered in a typical SPME development method procedure. It was possible to determine system equilibration times and use them to optimize sample volume and Henry's law constant. The developed model is relatively simple, fast, and can be recommended for optimization of extraction parameters for other analytes and SPME coatings. The diffusivity of analytes in a coating is an important property needed for improved characterization of existing and new SPME polymers and analytical method optimization.

Analyzing volatiles in brown rice vinegar by headspace solid-phase microextraction (SPME)–Arrow: Optimizing the extraction conditions and comparisons with conventional SPME

ABSTRACTThe ability to readily determine the composition of brown rice vinegar is important for quality assurance purposes. To that end, solid–phase microextraction (SPME)–Arrow method was optimized for the determination of volatile organic compounds (VOCs) from brown rice vinegar. Compared to traditional SPME fibers, SPME–Arrow has a larger sorbent-phase volume and is more durable. The SPME–Arrow conditions, including coating material, extraction temperature, extraction time, and NaCl concentration, were examined, which led to optimum extraction conditions that include: carboxen/polydimethylsiloxane (CAR/PDMS) fiber, 50°C, 30 min of SPME–Arrow, and 0% NaCl (i.e., no added NaCl). The developed method was compared to an optimized method based on conventional SPME. Twelve major VOCs, including acetates, alcohols, aldehydes, acids, and furan derivatives, were extracted by SPME–Arrow, while only seven VOCs were extracted using the traditional SPME. Moreover, SPME–Arrow extracted more 1.3–2 times more VOCs than SPME. Hence, the CAR/PDMS SPME–Arrow fiber is suitable for acquiring VOC profiles from brown rice vinegar.

Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software.

Determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air using solid-phase microextraction (SPME) is advantageous over other sampling techniques, but is often characterized by insufficient accuracies, particularly at longer sampling times. Experimental investigation of this issue and disclosing the origin of the problem is problematic and often not practically feasible due to high uncertainties. This research is aimed at developing the model of the TWA extraction process and optimization of TWA air sampling by SPME using finite element analysis software (COMSOL Multiphysics, Burlington, MA, USA). It was established that sampling by porous SPME coatings with high affinity to analytes is affected by slow diffusion of analytes inside the coating, an increase of their concentrations in the air near the fiber tip due to equilibration, and eventual lower sampling rate. The increase of a fiber retraction depth (Z) resulted in better recoveries. Sampling of studied VOCs using 23 ga Carboxen/polydimethylsiloxane (Car/PDMS) assembly at maximum possible Z (40 mm) was proven to provide more accurate results. Alternative sampling configuration based on 78.5 × 0.75 mm internal diameter SPME liner was proven to provide similar accuracy at improved detection limits. Its modification with the decreased internal diameter from the sampling side should provide even better recoveries. The results obtained can be used to develop a more accurate analytical method for determination of TWA concentrations of VOCs in air using SPME. The developed model can be used to simulate sampling of other environments (process gases, water) by retracted SPME fibers.

Comparison of two commercial solid‐phase microextraction fibers for the headspace analysis of volatile compounds in different pork and beef cuts

The performance of carboxen/polydimethylsiloxane (Car/PDMS) and divinylbenzene/Car/PDMS (DVB/Car/PDMS) fibers in extracting volatile organic compounds (VOCs) from different pork and beef cuts by headspace solid-phase microextraction (HS-SPME) was compared. A principal component analysis (PCA), cluster analysis (CA), and an analysis of variance were employed subsequently to evaluate the extraction performance. DVB/Car/PDMS fibers exhibited similar VOC profiles, but were less effective than Car/PDMS fibers which showed significantly (p < 0.05) higher extraction yields of major volatile groups including acids, alcohols, aldehydes, amines, and ketones in most of the tested meat cuts. There were no significant (p > 0.05) differences in the amount of aliphatic hydrocarbon, aromatic hydrocarbon, esters, and sulfur compounds extracted by both fibers. Car/PDMS exhibited significant (p < 0.05) differences in the amount of VOCs extracted from different meat cuts, while DVB/Car/PDMS fiber did not. These findings might provide insights into HS-SPME of VOCs from different meat cuts. Practical applications The application of HS-SPME for the determination of VOCs in raw or processed meats, particularly pork and beef cuts, has been extensively studied in recent years. Among the commercial SPME fibers available, Car/PDMS and DVB/Car/PDMS fibers are the most frequently employed. However, no adequate information regarding the selection process and comparison of the fibers has been provided. The results of this study demonstrate that the profile of VOCs in different cuts of pork and beef was strongly influenced by the type of fiber used for extraction. Thus, these findings might provide new insights into the HS-SPME analysis of VOCs in different meat cuts, especially the selection of fibers for the extraction of specific VOC analytes.

Volatile profile of soursop (Annona muricata L.) using HS-SPME-GC/MS

The aroma is one of the most appreciated sensorial attributes of fruit and one of the decisive factors in choosing a food. The flavor industry has grown significantly in recent years and the consumer's desire for new essences has given rise to the development of products from non-conventional fruits. The soursop (Annona muricata L.) is an important tropical fruit known to have a pleasant aroma and distinctive flavor. The objective of this work was to capture the volatiles from soursop pulp using solid phase microextraction (SPME) with the fibers 85 μm CAR/PDMS (carboxen/polydimethylsiloxane), 65 μm PDMS/DVB (polydimethylsiloxane/ divinylbenzene) and 50/30 μm DVB/CAR/PDMS (divinylbenzene/carboxen/ polydimethylsiloxane). The separation of volatile compounds was performed by GC-MS equipped with a nonpolar column (DB5-MS 30 m × 0.25 mm × 0,25 μm), and identified by comparing the mass spectra of the compounds of the samples with NIST (National Institute of Standards & Technology) and by comparison of the linear retention index (LRI). A total of 47 volatile compounds were identified with SPME technique, including 26 esters, 9 terpenes, 4 aldehydes, 1 alcohol, 2 aromatic hydrocarbons, 2 alkanes and 3 unidentified. Among the tested fiber which extracted more number of compounds was PDMS/DVB with a total of 39 compounds, and compounds with greater total area were the methyl hexanoate (39.19%), trans-2-methylhexanoate (25.23%), methyl butanoate (15.35%), trans-2-methyl-butenoate (4.41%) and trans-2-methyl octenoate (2.54%).

Evaluation of the Influence of Extraction Conditions on the Isolation and Identification of Volatile Compounds from Cagaita (Eugenia dysenterica) Using HS‑SPME/GC-MS

The objective of this study was to explore the extraction and identification of volatile organic compounds (VOCs) present in cagaita fruit (Eugenia dysenterica). Parameters such as type of extraction fiber, agitation, extraction time and extraction temperature were investigated. Initially, the VOCs were extracted using headspace solid-phase microextraction. Then, the compounds were identified using gas chromatography coupled to mass spectrometry. Results revealed the presence of at least 26 different compounds and the polyacrylate (PA) fiber promoted the extraction of a larger number of VOCs. Regarding the PA fiber, the most efficient extraction was achieved using a 50 rpm agitation at 45 oC for 30 min. The majority were monoterpenes (34.64%) and esters (36.28%). An increase in the extraction temperature promoted the isolation of more VOCs when using carboxen/polydimethylsiloxane (CAR/PDMS) and divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibers. However, these fibers allowed the isolation of a smaller number of VOCs. The extraction time and agitation had no significant influence.

Acrolein as a Major Volatile in the Early Stages of Fish Oil TAG Oxidation.

Fish oil rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) is known to have an unpleasant smell, even at low oxidation levels. Therefore, it is highly important to know the major volatiles formed during the early stages of fish oil oxidation. Comparative study with solid-phase microextraction (SPME) and static headspace (SHS) methods showed that 2-propenal (acrolein) was formed as the major volatile from the beginning of fish oil triacylglycerol (TAG) oxidation. The effectiveness of SPME extraction on each volatile was different from each fiber. Among the three different SPME fibers used in the present study, carboxen/polydimethylsiloxane (CAR/PDMS) was determined to be a better fiber for measuring the volatiles, including acrolein. The present study also showed that the non-selective SHS method is useful for determining the characteristic volatile formation in the early stages of fish oil TAG oxidation.

Rapid Analysis of 27 Volatile Sulfur Compounds in Wine by Headspace Solid-Phase Microextraction Gas Chromatography Tandem Mass Spectrometry

Volatile sulfur-containing compounds (VSCs) play an important role in wine aroma conferring at high concentrations unpleasant odors but also participating positively at low concentration. A large number of VSCs are formed at different stages of winemaking and storage. To monitor this phenomenon, a HS-SPME-GC-MS/MS method has been developed. The method is proposed in order to quantify 27 different sulfur-containing compounds. SPME extraction was performed using a carboxen-polydimethylsiloxane (CAR-PDMS) fiber, which resulted the most effective fiber coating. Time and temperature extraction conditions were optimized using response surface methodology. The selectivity and sensitivity of the method were considerably increased using triple-quadrupole in multiple reaction monitoring (MRM) mode. The number of VSCs analyzed in a single run was higher than in any other method previously reported using single-quadrupole MS or other detectors. The overall process was successfully applied to identify and quantify sulfur compounds both in white and red wines.