Headspace solid-phase microextraction gas chromatography-mass spectrometry analysis of volatiles in orujo spirits from a defined geographical origin

A headspace solid-phase microextraction (HS-SPME) and gas chromatography-selective ion monitoring/mass spectrometry (GC-SIM/MS) method was optimized for analysis of 22 volatile compounds in orujo spirit samples from the Geographic Denomination "Orujo de Galicia/Augardente de Galicia". HS-SPME experimental conditions, such as fiber coating, extraction temperature, extraction and pre-equilibrium time, sample volume, and the presence of salt, were studied to improve the extraction process. The best results were obtained using a 65 microm Carbowax-divinylbenzene fiber during a headspace extraction at 40 degrees C with constant magnetic stirring for 15 min and after a 5 min period of pre-equilibrium time. The sample volume was 6 mL of orujo containing 25% of NaCl, placed in 12 mL glass vials equipped with a screw cap and PTFE/silicone septum. Desorption was performed directly in the gas chromatograph injector port for 5 min at 250 degrees C using the splitless mode. The proposed method is sensible (with detection limits between 0.0045 and 0.2399 mg/L), precise (with coefficients of variation in the range 0.99-8.18%), and linear over more than 1 order of magnitude. The developed method presented recoveries comprised between 76.0 and 112.4%. The applicability of the new method was demonstrated by determining the considered 22 volatile compounds in nine orujo commercial samples with quality and origin brands.     

Chemical and sensory quantification of geosmin and 2-methylisoborneol in rainbow trout (Oncorhynchus mykiss) from recirculated aquacultures in relation to concentrations in basin water

Globally, aquaculture systems with water recirculation experience increasing problems with microbial taste and odor compounds (TOCs) such as geosmin and 2-methylisoborneol (MIB). This study investigated the content of geosmin and MIB in water and the flesh of 200 rainbow trouts from eight recirculated aquaculture systems in Denmark. TOC content in the fish flesh was measured by a dynamic headspace extraction method and was evaluated by a sensory panel. The results showed significant correlations between TOC content in water and fish and between chemical analysis and sensory perception. When geosmin exceeded 20 ng/L in the water, 96% of the fish had an intense muddy flavor, but below 10 ng geosmin/L, 18% of the fish (only 3% in special depuration ponds) had an intense muddy flavor. The results indicate that TOC levels <10 ng/L will ensure that a negligible portion of the fish obtains an unpalatable taste and flavor due to TOCs.     

Development of an improved liquid phase microextraction technique and its application in the analysis of flumetsulam and its two analogous herbicides in soil

An improved liquid phase microextraction (LPME) technique has been developed. As part of this technique, analytes were extracted into an extractant microdrop which was laid on the cone-shaped bottom of a PCR tube (polychloroprene rubber tube) but not at the needle tip of a microsyringe, and the sample vial and PCR tube were horizontally placed so that the extractant was not affected by the force of vertical orientation (gravity and floating force). The stability of the extractant microdrop increased greatly, and the selection of extractant was extended. In this work, flumetsulam and its two analogous herbicides were chosen as model analytes in investigating the feasibility of the new pretreatment method by coupling it to high-performance liquid chromatography (HPLC). Under the optimized experimental conditions, the linear range and the limits of detection (S/N = 3) were 0.01-5 microg/mL (r = 0.9997) and 0.8 ng/mL for flumetsulam, 0.002-5 microg/mL (r = 0.9994) and 0.5 ng/mL for analogue 1, and 0.002-1 microg/mL (r = 0.9993) and 0.5 ng/mL for analog 2, respectively. The inter- and intraday reproducibilities (RSD) were below 5.3 and 4.5%, respectively. Good recoveries that ranged from 79.4 to 115.0% were obtained in the analysis of real soil samples. The extraction efficiency of the improved method was 4-8 times higher than that of the conventional liquid phase microextraction method. The novel, simple, rapid, sensitive technique is very suitable for extraction of apolar and medium polar analyte in complex environmental samples.     

Headspace solid phase microextraction applied to the analysis of organophosphorus insecticides in strawberry and cherry juices

A method based on a headspace solid phase microextraction (HS-SPME) technique followed by gas chromatography with flame thermionic and mass spectrometric detection was developed for the determination of seven organophosphorus (OPs) insecticide residues in strawberry and cherry juice samples. The extraction capacities of four fiber coatings, polyacrylate (PA 85 microm), poly(dimethylsiloxane) (PDMS 100 microm), carbowax-divinylbenzene (CW-DVB 65 microm), and poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB 65 microm), have been studied and compared. The method was developed using spiked strawberry and cherry juices in a concentration range of 0.5-50 microg/L. The PDMS 100 microm fiber showed good extraction efficiency for the target compounds. An increase in the extraction efficiency of OP insecticides was observed when the parameters affecting the HS-SPME process such as temperature, extraction time, salt additives, stirring rate, pH, and effect of dilution were optimized. Good linearity of compounds was observed in the tested concentration range. The relative standard deviations were found to be <20%. The limits of detection were between 0.025 and 0.050 microg/L. The mean relative recoveries ranged from 82 to 102%.     

Optimization of multiple headspace solid-phase microextraction for the quantification of volatile compounds in dry fermented sausages

Multiple headspace solid-phase microextraction (HS-SPME) is a stepwise method that eliminates the influence of the matrix sample on the quantitative analysis of solid samples. The process was optimized for the analysis of volatile compounds in dry fermented sausages by gas chromatography and mass spectrometry. Different amounts of fermented sausages and different vial volumes were studied to obtain the theoretical exponential decay of the peak area of the four successive extractions in order to calculate the total area in the sausage. The highest number of volatile compounds analyzed by multiple HS-SPME in dry fermented sausages was obtained in a 10 mL headspace vial with 0.07 g of sample in the presence of water, 0.75 mg butylated hydroxytoluene, and 0.5 g sodium chloride. Finally, the method was characterized in terms of linearity and detection limits and applied to analyze the volatile compounds present in fermented sausages manufactured with either nitrate or nitrite.     

Headspace solid-phase microextraction method for the study of the volatility of selected flavor compounds

Changes in the volatility of selected flavor compounds in the presence of nonvolatile food matrix components were studied using headspace solid-phase microextraction (HS-SPME) combined with GC-MS quantification. Time-dependent adsorption profiles to the SPME fiber and the partition coefficients between different phases were obtained for several individual volatiles, showing that HS-SPME analysis with a short sampling time can be used to determine the "true" headspace concentration at equilibrium between the headspace and a sample matrix. Equilibrium dialysis followed by HS-SPME/GC-MS was carried out to confirm the ability of HS-SPME extraction for monitoring the free volatile compounds in the presence of proteins. In particular, a short sampling time (1 min) avoided additional extraction of volatiles bound to the protein. Interactions between several selected flavor compounds and nonvolatile food matrix components [beta-lactoglobulin or (+)-catechin] were also studied by means of HS-SPME/GC-MS analysis. The volatility of ethyl hexanoate, heptanone, and hexanal was significantly decreased by the addition of beta-lactoglobulin compared to that of isoamyl acetate. Catechin decreased the volatility of ethyl hexanoate and hexanal by 10-20% and increased that of 2-heptanone by approximately 15%. This study indicates that HS-SPME can be a useful tool for the study of the interactions between volatile compounds and nonvolatile matrix components provided the kinetic and thermodynamic behavior of the volatiles in relation to the fiber chosen for the studies is carefully considered.     

Screening of tropical fruit volatile compounds using solid-phase microextraction (SPME) fibers and internally cooled SPME fiber

In this study, the optimization and comparison of an internally cooled fiber [cold fiber with polydimethylsiloxane (PDMS) loading] and several commercial solid-phase microextraction (SPME) fibers for the extraction of volatile compounds from tropical fruits were performed. Automated headspace solid-phase microextraction (HS-SPME) using commercial fibers and an internally cooled SPME fiber device coupled to gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile compounds of five tropical fruits. Pulps of yellow passion fruit (Passiflora edulis), cashew (Anacardium occidentale), tamarind (Tamarindus indica L.), acerola (Malphigia glabra L.), and guava (Psidium guajava L.) were sampled. The extraction conditions were optimized using two experimental designs (full factorial design and Doehlert matrix) to analyze the main and secondary effects. The volatile compounds tentatively identified included alcohols, esters, carbonyl compounds, and terpernes. It was found that the cold fiber was the most appropriate fiber for the purpose of extracting volatile compounds from the five fruit pulps studied.     

Quantitative determination of geosmin in red beets (Beta vulgaris L.) using headspace solid-phase microextraction

An improved analytical method for the determination of geosmin in red beets was developed using headspace solid-phase microextraction (HSPME). Volatiles of beet juice were extracted in headspace for 2 h using a polydimethylsiloxane/divinylbenzene fiber, thermally desorbed from the fiber, and analyzed by gas chromatography. The HSPME method was determined to be suitable for geosmin analysis as evidenced by high relative recovery (99.2%), low relative standard deviation (7.48%), and reasonable detection limit (1 microg/kg of beet root tissue). The concentrations of geosmin in four beet cultivars ranged from 9.69 +/- 0.22 to 26.7 +/- 0.27 microg/kg, depending on cultivar.     

Characterization of pyrazines in some Chinese liquors and their approximate concentrations

Pyrazines are very important impact aroma compounds in Chinese liquors. The identification of pyrazine derivatives was carried out by liquid-liquid extraction (LLE). The liquor sample was adjusted to the H(+) concentration of 1 N with 12 N HCl and then concentrated by rotatory evaporator under vacuum condition. The concentrated liquor was extracted by diethyl ether, and the residual aqueous phase was adjusted to pH 10. The basic compounds were detected and identified by gas chromatography (GC)-mass spectrometry (MS). A total of 27 pyrazines were identified in Chinese liquors, mainly alkyl- and acetylpyrazines. A method for determining pyrazines in Chinese liquors was developed. It involves extraction by headspace (HS) solid phase microextraction (SPME) and determination using GC-flame thermionic detector (FTD). The optimum method was that the sample alcohol concentration was diluted to 12% vol by freshly redistilled-deionized water, and the diluted samples were saturated with NaCl and equilibrated at 50 degrees C for 15 min and extracted for 30 min at the same temperature. The developed method enabled detection limits of <200 ng/L. Linearity (R(2) > 0.99) and recovery rate were satisfied in all cases. Pyrazines of 12 commercial typical Chinese liquors were quantified by HS-SPME followed by GC-FTD and had a wide range of concentration.     

Improved malonaldehyde assay using headspace solid-phase microextraction and its application to the measurement of the antioxidant activity of phytochemicals

A modified malonaldehyde (MA) assay for antioxidant activity, which involves derivatization and headspace solid-phase microextraction (HS-SPME) was developed and validated. The recovery of MA as 1-methylpyrazole (product of MA and N-methylhydrazine) from a headspace of an aqueous solution containing MA, buffer, surfactant, and cod liver oil using HS-SPME with a PDMS/DVB fiber was 91.3 +/- 3.38%. MA was analyzed by a gas chromatograph with a nitrogen-phosphorus detector, and its detection limit was 0.0103 nmol/mL. The antioxidant activities of natural compounds were determined as the percentage inhibition of MA formed from cod liver oil oxidized by Fenton's reagents in the above aqueous solution. Sesamol inhibited MA formation most (86.1%), followed by eugenol (84.4%), capsaicin (80.7%), ethylvanillin (45.3%), and vanillin (31.6%) at a level of 50 microg/mL. This method did not require any organic solvents and is a simple, fast, and a highly sensitive method for MA determination.     

Comparison of static headspace, headspace solid phase microextraction, headspace sorptive extraction, and direct thermal desorption techniques on chemical composition of French olive oils

Static headspace (SHS), headspace solid phase microextraction (HS-SPME), headspace sorptive extraction (HSSE), and direct thermal desorption (DTD) were applied to the analysis of four French virgin olive oils from Corsica. More than 60 compounds were isolated and characterized by GC-RI and GC-MS. SHS was not suited to the characterization of olive oil volatile compounds because of low sensitivity. The SPME and HSSE techniques were successfully applied to olive oil headspace analysis. Both methods allow the characterization of volatile compounds (mainly C(6) aldehydes and alcohols), which contribute significantly to the "green" flavor note of virgin olive oils. The PDMS stir bar showed a higher concentration capacity than a DVB/CAR/PDMS SPME fiber due to the higher volume of polymeric coating. DTD was a very good tool for extracting volatile and especially semivolatile compounds, such as sesquiterpenes, but requires a significant investment like that for HSSE. Finally, SPME may be a more appropriate technique for routine quality control due to its operational simplicity, repeatability, and low cost.     

Determination of the microbial origin of geosmin in Chinese liquor

Geosmin is the major cause of the common earthy off-flavor in light-aroma type Chinese liquor and, thus, highly detrimental to the aromatic quality. To find out its origin, the evolving process of geosmin in light-aroma type liquor making was monitored, and microbial analysis of Daqu containing geosmin was carried out. The results showed that geosmin appeared in all the fermented sorghums at different fermentation periods. About 57% geosmin in the fermented sorghums was distilled into liquor. During the distillation process, the peak of geosmin concentration appeared when alcohol content was 50-60% vol. More importantly, high geosmin content was observed during the Daqu-making process. Furthermore, five Streptomyces strains were isolated from different types of Daqu used for the fermentation of light-aroma type liquor. All of them produced only geosmin as the main volatile metabolite but no 2-methylisoborneol (2-MIB). It appears that microorganisms developing in Daqu are responsible for the presence of geosmin in liquor. Because of the relatively low detection threshold estimated at 110 ng/L in 46 vol % hydroalcoholic solution, the presence of geosmin in Daqu may pose a risk for Chinese liquor producers.     

A new method for the determination of carbonyl compounds in wines by headspace solid-phase microextraction coupled to gas chromatography-ion trap mass spectrometry

A new analytical method for the determination of 18 carbonyl compounds [2,3-pentadione, hexanal, (E)-2-hexen-1-al, octanal, acetoin, (E)-2-octenal, furfural, decanal, (E)-2-nonenal, benzaldehyde, 5-methylfurfural, (E,E)-2-cis-6-nonadienal, β-damascenone, phenylacetaldehyde, acetophenone, (E,E)-2,4-decadienal, benzophenone, and vanillin] in wines using automated headspace solid-phase microextraction (HS/SPME) coupled to gas chromatography-ion trap mass spectrometry (GC-ITMS) was developed. Five fibers with different polarities were tested, and a study of the influence of various factors such as time and extraction temperature, desorption time and temperature, pH, and ionic strength and content in tannins, anthocyans, sucrose, SO(2), and alcoholic degree was conducted. These factors were optimized using a synthetic wine doped with the different analytes. The proposed method affords wide ranges of linearity, good linearity (r(2) > 0.998), values of repeatability and reproducibility lower than 5.5% of RSD, and detection limits ranging from 0.62 μg/L for β-damascenone to 129.2 μg/L for acetoin. Therefore, the optimized method was applied to the quantitative analysis of the aforementioned analytes in real samples of wines.     

Analysis of 2-methylisoborneol and geosmin in catfish by microwave distillation--solid-phase microextraction

The semivolatile cyclic alcohols 2-methylisoborneol (MIB) and geosmin (GSM) impart muddy or musty flavors to water and food products. A rapid quantitative analytical technique has been developed whereby microwave distillation is used to remove the volatile organic compounds from a lipophilic matrix into an aqueous matrix. Solid-phase microextraction (MD-SPME) is then used to extract and concentrate the analytes, which are then desorbed in the injection port of a gas chromatograph/mass spectrometer (GC/MS) for analysis. Limits of detection are 0.01 microg/kg and limits of quantification are 0.1 microg/kg. MD-SPME is comparable in precision, requires no solvents, and is faster than current methods of analysis. This methodology allows detection of MIB and GSM at concentrations below human sensory thresholds in fish tissue.     

Solventless Microextraction Techniques for Determination of Trihalomethanes by Gas Chromatography in Drinking Water

Three different solventless sample preparation techniques based on microextraction, membrane extraction, and headspace extraction have been developed and optimized for determination of trihalomethanes in drinking water by gas chromatography electron capture detector and mass spectrometry detection. The techniques employed were headspace (HS) solid-phase microextraction, hollow fiber liquid-phase microextraction (HFLPME) and HS extraction. All techniques used were optimized with different experimental designs in order to select the most relevant variables which significantly affect the different processes. The different analytical figures of merit such as limit of detection (LOD), limit of quantification, reproducibility, accuracy, and linear dynamic range were obtained. The new HFLPME method applied used a hollow fiber membrane of polypropylene and the optimized variables were extraction time, extraction temperature, and salting-out effect. The software MODDE 6.0 was used and its design was one central composite on face with a total of 17 runs. The best conditions for the HFLPME were 20 min, 40°C, and 10% NaCl, respectively. The LODs ranged from 0.018 μg·L⁻¹ (for CHClBr₂) to 0.049 μg·L⁻¹ (for CHBr₃), being this technique the most sensitive one among those studied. Finally, after having optimized the sample preparation techniques and chromatographic conditions, several water samples were taken in two different water treatment plants in Spain (Zaragoza) and Colombia (Viterbo, Caldas). The results obtained are shown and discussed.     

Determination of geosmin, 2-methylisoborneol, and a musty-earthy odor in wheat grain by SPME-GC-MS, profiling volatiles, and sensory analysis

Geosmin and 2-methylisoborneol-compounds responsible for the musty-earthy off-odor of wheat grain, were isolated by SPME and analyzed by GC-MS. Carboxen/PDMS/DVB fiber coating was selected because of its highest extraction efficiency. Concentrations of geosmin and 2-methylisoborneol as low as 0.001 microg/kg were detected in SIM mode using ion trap mass spectrometer. Apart from GC-MS determination of geosmin and 2-methylisoborneol, various methods for evaluating the musty-earthy off-odor caused by these compounds in wheat grain are presented. Sensory profile analysis differentiated wheat grain into sound and off-flavored, but the method was tedious. Similar groupings, however, were obtained using more rapid methods such as comparison of volatile profiles using SPME-fast GC with PCA projection of data and metal oxide (MOS) based electronic nose.     

Determination of 2,4,6-trichloroanisole and 2,4,6-tribromoanisole in wine using microextraction in packed syringe and gas chromatography-mass spectrometry

A selective and fast method for the quantitative determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine was developed. Microextraction in packed syringe (MEPS) was optimized for the extraction and preconcentration of the analytes using extremely small volume samples (0.1-1 mL). For GC-EI-MS, the limit of detection (LOD) for red and white wine was in the range 0.17-0.49 microg L(-1) for TCA and TBA. In addition to GC-EI-MS both GC-NCI-MS and GC-HRMS were used to further improve both selectivity and sensitivity. The lowest LODs were achieved using GC-HRMS in the EI mode. In red and white wine samples the LODs were between 0.22-0.75 ng L(-1) for TCA and TBA. The reproducibility and linearity for the GC-HRMS method was good, with RSD-values of 4-10% for spiked red wine samples at 1 ng L(-1) and linearity with R (2) > 0.962 over a concentration range of 1 to 100 ng L(-1).     

Essential oil composition of sachalinmint from Norway detected by solid-phase microextraction and gas chromatography-mass spectrometry analysis

The essential oil of leaves and flowers of sachalinmint [Mentha sachalinensis (Briq.) Kud?] grown in Norway (Trondheim) has been studied by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry analysis (GC-MS). The essential oil content increased linearly in acropetal direction from 1.08% (0-20 cm plant height) to 1.75% (60-80 cm; young leaves and flowers). The steam-distilled samples showed a minor complex matrix with a very high menthol and a much lower menthone content (87.89 and 4.05%, respectively). From testing of HS-SPME unequilibrated exposure times ranging from 10 s to 5 min, an extraction time of 30 s was found to be sufficient to detect both low- and high-eluting compounds. Comparison of HS-SPME and steam-distilled samples established that the same tendencies of increasing menthol/menthone content in the basipetal/acropetal direction could be detected by both analysis methods. With regard to the extraction efficiency, HS-SPME gave additional detailed information about less important terpenic compounds.     

Solid-phase microextraction and gas chromatography olfactometry analysis of successively diluted samples. A new approach of the aroma extract dilution analysis applied to the characterization of wine aroma

The relationship between the composition and the aroma of the wine can be established by using gas chromatography with olfactometric detection (sniffing or GCO), which combines the chromatographic response with the human nose response. To evaluate the contribution of the odor compounds in wine aroma, we designed a new approach of the aroma extract dilution analysis (AEDA) that lies in the GCO analysis of serially diluted wine samples using headspace solid-phase microextraction (HS-SPME) as the extraction technique. The fiber coating used was Flex divinyl-carboxen-polydimethylsiloxane. The method developed was applied to determine the aromatic composition of a red Grenache wine from Priorat (Spain). The method allows 38 important odorants to be determined in the AEDA study, 30 of them precisely identified. These results are similar to those reported by other studies related to this variety of wine. HS-SPME is a suitable technique to obtain representative extracts of wine aroma with several advantages such as simplicity, speediness, and little sample manipulation.     

Development of a solid-phase extraction method for phenoxy acids and bentazone in water and comparison to a liquid-liquid extraction method

A rapid solid-phase extraction (SPE) method was developed for the determination of bentazone and the phenoxy acids 2,4-D, dichlorprop, MCPA, and mecoprop in Norwegian environmental water samples. Cartridges with a high-capacity cross-linked polystyrene-based polymer were used for off-line preconcentration. The effects of elution solvent, elution volume, sample volume, sorbent mass, pH, and flow rate on the recoveries of the pesticides were investigated using HPLC. Average recovery of >90% was achieved with 500 mg sorbents using 2 mL of methanol with 5% NH3 as elution solvent. The recoveries were independent of sample pH in the tested range of pH 1-7. Using a sample volume of 200 mL, the limits of determination for the phenoxy acids and bentazone are 0.02 microg/L. Sample volumes up to 2000 mL at a flow rate of 60 mL/min could be handled without any loss of analytes, which makes it possible to lower the limits of determination. The SPE method was compared to a routinely used liquid-liquid extraction method. Three different water matrices spiked at 1.0 and 0.05 microg/L were extracted, and the quantification was performed by GC-MS. Both methods permitted the determination of phenoxy acids and bentazone in distilled water, creek water, and well water down to a level of 0.05 microg/L with recoveries >80% for 200 mL samples. Important advantages of the SPE method compared to the liquid-liquid extraction method were the short extraction times, lack of emulsions, use of disposable equipment, and reduced consumption of organic solvents.