Multidimensional Gas Chromatography-mass Spectrometry Research Articles

Analysis, occurrence and potential sensory significance of aliphatic aldehydes in white wines

An analytical method was developed for C8–C11 aliphatic aldehydes in wine consisting of solid phase extraction (SPE) followed by multidimensional gas chromatography/mass spectrometry (MDGC/MS). The method achieves low detection limits (<30ngL−1), minimises problems of blank contamination and shows high repeatability (RSD%<5%), but strong matrix effects were noticed during validation. These matrix effects were attributed to strong interactions between aliphatic aldehydes and other matrix elements. Three fractions were differentiated: free extractable aldehydes, aldehydes bound in hydrophilic complexes (extractable in the presence of acetaldehyde) and aldehydes bound in hydrophobic complexes (extractable in the presence of heptanal). The distribution of the three aldehyde species in wine samples was estimated using a surrogate (3,5,5-trimethylhexanal) and an internal standard (methyl phenylacetate) in double determinations (directly and after incubation with 1000mgL−1 acetaldehyde). These components had a clear additive sensory effect in mixtures and odour thresholds in wine were very low. This caused that although they were present at very low levels, in 2 out of 24 white wine samples were clearly above threshold, and in six more were at levels close to threshold. These results suggest that these components are active contributors to the citrus fruit notes of some white wines.

Quantification of free and total bisphenol A and bisphenol B in human urine by dispersive liquid–liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography–mass spectrometry (MD–GC/MS)

A novel method combining dispersive liquid–liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography coupled to mass spectrometry was developed for the determination of free and total bisphenol A (BPA) and bisphenol B (BPB) in human urine samples. The DLLME procedure combines extraction, derivatization and concentration of the analytes into one step. Several important variables influencing the extraction efficiency and selectivity such as nature and volume of extractive and dispersive solvents as well as the amount of acetylating reagent were investigated. The temperature and time to hydrolyze BPA and BPB conjugates with a β-glucuronidase and sulfatase enzyme preparation were also studied. Under the optimized conditions good efficiency extraction (71–93%) and acceptable total DLLME yields (56–77%) were obtained for both analytes. Matrix-matched calibration curves were linear with correlation coefficients higher than 0.996 in the range level 0.1–5 μg/l, and the relative standard deviations (%RSD) were lower than 20% ( n = 6). The limits of detection were 0.03 and 0.05 μg/l for BPA and BPB, respectively. The applicability of the proposed method for determining urinary free and total BPA and BPB was assessed by analyzing the human urine of a group of 20 volunteers. Free BPA was detected in 45% of the sample whereas total BPA was detected in 85% of the samples at concentrations ranging between 0.39 and 4.99 μg/l. BPB was detected in conjugated form in two samples.

Fast analysis of multiple pesticide residues in apple juice using dispersive liquid–liquid microextraction and multidimensional gas chromatography–mass spectrometry

A method for the rapid trace analysis of 24 residual pesticides in apple juice by multidimensional gas chromatography–mass spectrometry (MD-GC/MS) using dispersive liquid–liquid microextraction (DLLME) was developed and optimized. Several parameters of the extraction procedure such as type and volume of extraction solvent, type and volume of dispersive solvent and salt addition were evaluated to achieve the highest yield and to attain the lowest detection limits. The DLLME procedure optimized consists in the formation of a cloudy solution promoted by the fast addition to the sample (5 ml) of a mixture of carbon tetrachloride (extraction solvent, 100 μl) and acetone (dispersive solvent, 400 μl). The tiny droplets formed and dispersed among the aqueous sample solution are further joined and sedimented (85 μl) in the bottom of the conical test tube by centrifugation. Once extracted, all the 24 pesticides were directly injected and separated by a dual GC column system, comprising a short wide-bore DB-5 capillary column with low film thickness connected by a Deans switch system to a second chromatographic narrower column, with identical stationary phase. The instrumental setting used, in combination with carefully optimized operational fast GC and MS parameters, markedly decreased the retention times of the targeted analytes. The total chromatographic run was 8 min. Mean recoveries for apple juice spiked at three concentrations ranged from 60% to 105% and the intra-repeatability ranged from 1% to 21%. The limits of detection of the 24 pesticides ranged from 0.06 to 2.20 μg/L. In 2 of a total of 28 analysed samples were found residues of captan, although at levels below the maximum limit legal established.

Occurrence of 2,2,4-trimethyl–1,3-pentanediol monoisobutyrate (Texanol®) in foods packed in polystyrene and polypropylene cups

After simultaneous distillation–extraction (SDE) of foods packed in polystyrene (n = 77) and polypropylene cups (n = 42) from 61 different suppliers, coupled capillary gas chromatography–mass spectrometric (HRGC–MS) analyses indicated the presence of diastereomers of 2,2,4-trimethyl–1,3-pentanediol monoisobutyrate (TMPD-MIB; Texanol®), a known coalescent of paints and printing inks. The contaminant was found in 55 and 50% of the polystyrene and polypropylene packed samples, respectively. Amounts ranged 1.2–64.5 µg kg−1 in polystyrene cups (average 25.1 µg kg−1) and 0.9–45.7 µg kg−1 in polypropylene cups (average 10.8 µg kg−1). The origin of Texanol® in the printed plastic cups was demonstrated by separate HRGC–MS analysis, showing amounts in the higher µg kg−1 range. In addition, the presence of two pairs of enantiomers, both found to be racemic by enantioselective multi-dimensional gas chromatography–mass spectrometry (enantio-MDGC–MS), excluded it being of natural origin. The detection limit of overall procedure (DLOP) and the reliable quantification limit (RQL) were 0.2 and 0.9 µg kg−1, respectively. As the diester, 2,2,4-trimethyl–1,3-pentanediol diisobutyrate (TXIB), is on the EU list of regulated substances (restricted to single-use gloves only) with a migration limit of 5 mg kg−1 in food and is metabolised rapidly by hydrolysis, the observed migration of the monoester Texanol® at the µg kg−1 level poses no risk of adverse effects.

Multidimensional gas chromatography–mass spectrometry determination of 3-alkyl-2-methoxypyrazines in wine and must. A comparison of solid-phase extraction and headspace solid-phase extraction methods

Two different strategies for the quantitative determination of 3-alkyl-2-methoxypyrazines in wine and must have been developed and validated. Comparison between both the techniques has been presented and the most adequate has been applied to the determination of these compounds in different samples of wine, made from several varieties of grapes, and also in different samples of must made from Cabernet Sauvignon grapes. Both the methods consisted of a dynamic headspace coupled with a solid-phase extraction (HS–SPE) and solid-phase extraction (SPE) directly from the sample, coupled with multidimensional gas chromatography–mass spectrometry system (MDGC–MS). Both of them require resins LiChrolut EN, and analyte elution has been carried out with dichloromethane. The repeatability of both methodologies was evaluated at two concentration levels. The relative standard deviations (RSD%) were acceptable in every case, but smaller when working with HS–SPE. The recoveries obtained for the three analytes with the two methodologies were almost 100%, with the exception of IBMP, which had a recovery of only 70% with HS–SPE. The linearity was satisfactory with both methods for the range of occurrence of methoxypyrazines in wine and must. The limits of detection of the direct SPE technique were much lower than those of HS–SPE in every case. Direct SPE method detection limits ranged from 0.09 to 0.15 ng L −1. The method based on direct SPE was chosen finally because it had better detection limits and was easier and quicker than the HS–SPE-based method. It has been applied to the determination of these components in 36 wine and 17 musts samples. The quantitative results suggest that the Spanish wines show meaningless amounts of these compounds. IBMP has been found just in between 1.9 and 15 ng L −1.

Rapid determination of trans-resveratrol in red wine by solid-phase microextraction with on-fiber derivatization and multidimensional gas chromatography–mass spectrometry

There has been considerable public interest and a growing number of scientific studies linking certain phenolic compounds in grapes and wines, particularly trans-resveratrol ( trans-3,5,4′-trihydroxystilbene, TRA), to human health benefits. Typical TRA concentrations in wine are very low. It is a polar compound with very low volatility, which makes it difficult to extract and to separate on a gas chromatography (GC) column without derivatization. In this study, a new method for trace analysis of TRA was developed using solid-phase microextraction (SPME) with on-fiber silylation derivatization. Multidimensional GC equipped with a heartcut valve and cryogenic focusing was coupled with a mass-selective detector and used for improved separations and analysis. The effects of SPME fiber selection, extraction time, temperature, and desorption time were investigated. The derivatization conditions, time/temperature and the volume of derivatization reagent were also optimized. The calibration curve was linear over the concentration range from 10 ng L −1 to 5 mg L −1, with a correlation coefficient of 0.9996. The average recovery of TRA in red wine was 83.6 ± 5.6%. The method detection limit (MDL) for TRA in ethanol:water (12.5:87.5, v/v) solution in this study was 7.08 ng L −1 whereas the MDL for TRA in pure water was 2.85 ng L −1. The new method was used to test the TRA content in six selected Iowa red wine samples. Measured concentrations varied from 12.72 to 851.9 μg L −1.

Simultaneous Chemical and Sensory Characterization of Volatile Organic Compounds and Semi‐Volatile Organic Compounds Emitted from Swine Manure using Solid Phase Microextraction and Multidimensional Gas Chromatography–Mass Spectrometry–Olfactometry

Swine manure is associated with emissions of odor, volatile organic compounds (VOCs) and other gases that can affect air quality on local and regional scales. In this research, a solid phase microextraction (SPME) and novel multidimensional gas chromatography-mass spectrometry-olfactometry (MDGC-MS-O) system were used to simultaneously identify VOCs and related odors emitted from swine manure. Gas samples were extracted from manure headspace using Carboxen/polydimethylsiloxane (PDMS) 85-microm SPME fibers. The MDGC-MS-O system was equipped with two columns in series with a system of valves allowing transfer of samples between columns (heartcutting). The heartcuts were used to maximize the isolation, separation, and identification of compounds. The odor impact of separated compounds was evaluated by a trained panelist for character and intensity. A total of 295 compounds with molecular weights ranging from 34 to 260 were identified. Seventy one compounds had a distinct odor. Nearly 68% of the compounds for which reaction rates with OH* radicals are known had an estimated atmospheric lifetime <24 h.

Pressure-adjusted continual flow heart-cutting for the high throughput determination of amphetamine-type stimulant drugs in whole blood by fast multidimensional gas chromatography–mass spectrometry

Innovative features and technical improvements in modern bench-top quadrupole gas chromatograph–mass spectrometer (GC–MS) have prepared the way for faster and more cost-effective applications while still maintaining sufficient chromatographic resolution, speed of MS data acquisition and reliability of analytical methodology. In this paper, a short wide-bore capillary column with low film thickness (5m×0.32mm i.d., 0.1μm) was used a pre-fractionating column and only chosen heart-cuts were transferred to the second chromatographic dimension (15m×0.25mm i.d., 0.25μm) by means of a pressure-adjusted continual flow type switching device for quantification of five common amphetamine-type stimulant drugs. The instrumental setting used, in combination with carefully optimized operational fast GC and MS parameters, markedly decreased the retention times of the targeted analytes, e.g., amphetamine 0.891min and methamphetamine 1.037min, and the total chromatographic runtime (1.700min), as well as reducing the need for continuous cleaning of the MS ion source and increasing column life compared with conventional GC–MS approaches. The performance of the instrumental configuration and analytical method was evaluated in validation experiments and the method was also applied to authentic samples. The method demonstrates the potential of fast GC–MS in combination with a gas-phase microfluidic Deans switch device for analysing of (semi)volatile compounds, such as amphetamine-type stimulant (ATS) drugs. This should be particularly useful in modern laboratories aiming at cost-efficient analysis as well as the optimum use of available laboratory capacity and instrumentation.

Determination of characteristic odorants from Harmonia axyridis beetles using in vivo solid-phase microextraction and multidimensional gas chromatography–mass spectrometry–olfactometry

Homeowners, small fruit growers, and wine makers are concerned with noxious compounds released by multicolored Asian ladybird beetles ( Harmonia axyridis, Coleoptera: Coccinellidae). A new method based on headspace solid-phase microextraction (HS-SPME) coupled with multidimensional gas chromatography–mass spectrometry–olfactometry (MDGC–MS–O) system was developed for extraction, isolation and simultaneous identification of compounds responsible for the characteristic odor of live H. axyridis. Four methoxypyrazines (MPs) were identified in headspace volatiles of live H. axyridis as those responsible for the characteristic odor: 2,5-dimethyl-3-methoxypyrazine (DMMP), 2-isopropyl-3-methoxypyrazine (IPMP), 2- sec-butyl-3-methoxypyrazine (SBMP), and 2-isobutyl-3-methoxypyrazine (IBMP). To the best of our knowledge this is the first report of H. axyridis releasing DMMP and the first report of this compound being a component of the H. axyridis characteristic odor. Besides the MPs, 34 additional compounds were also identified. Quantification of three MPs (IPMP, SBMP and IBMP) emitted from live H. axyridis were performed using external calibration with HS-SPME and direct injections. A linear relationship ( R 2 > 0.9951 for all 3 MPs) between MS response and concentration of a standard was observed over a concentration range from 0.1 ng L −1 to 0.05 μg L −1 for HS-SPME–GC–MS. The method detection limits (MDL) based on multidimensional GC–MS with narrow heart-cut approach for three MPs were estimated to be between 0.020 and 0.022 ng L −1. This represents a 38.9–52.4% improvement in sensitivity compared to GC–MS with full heart-cut method. This methodology is applicable for in vivo determination of odor-causing chemicals associated with emissions of volatiles from insects.

Solid phase extraction, multidimensional gas chromatography mass spectrometry determination of four novel aroma powerful ethyl esters: Assessment of their occurrence and importance in wine and other alcoholic beverages

A method for the quantitative determination of four powerful aromatic ethyl esters recently identified in some wines has been developed, validated and applied to the determination of these compounds in different samples of wine, whisky and brandy. Ethyl 2-, 3-, and 4-methylpentanoate and ethyl cyclohexanoate are extracted from 100 ml of sample by solid phase extraction (SPE) on a 200 mg LiChrolut EN bed. Major compounds are eliminated by rinsing with a water–methanol (50:50) solution containing 1% sodium bicarbonate, and analytes are eluted with 1.5 ml of dichloromethane. Fifty microlitres of this extract are then injected in a multidimensional gas chromatography–mass spectromety (GC–GC–MS) system. Recoveries in the SPE are quantitative. Method repeatability is satisfactory (5–12% for a 5–10 ng l −1 level, and less than 7% for 25–50 ng l −1 level), the method linearity holds along the whole range of occurrence of analytes (2–2700 ng l −1), and the signal is independent on the matrix. Method detection limits are below 1 ng l −1 in all cases. Results suggest that these compounds are formed by the slow esterification with ethanol of the corresponding acids formed by different microorganisms. The levels of these compounds are above the corresponding thresholds in most samples of aged wines or distillates, but are particularly high in some sweet wines, whiskeys and brandies where they may constitute the most important contributors to the sweet-fruity notes reaching concentrations up to 85–350 times higher than the corresponding odor thresholds.

Characterization of Livestock Odors Using Steel Plates, Solid-Phase Microextraction, and Multidimensional Gas Chromatography–Mass Spectrometry–Olfactometry

Livestock operations are associated with emissions of odor, gases, and particulate matter (PM). Livestock odor characterization is one of the most challenging analytical tasks. This is because odor-causing gases are often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objective of this project was to develop a set of characteristic reference odors from a swine barn in Iowa and, in the process, identify compounds causing characteristic swine odor. Odor samples were collected using a novel sampling methodology consisting of clean steel plates exposed inside and around the swine barn for ≤1 week. Steel plates were then transported to the laboratory and stored in clean jars. Head-space solid-phase microextraction was used to extract characteristic odorants collected on the plates. All of the analyses were conducted on a gas chromatography-mass spectrometry-olfactometry system where the human nose is used as a detector simultaneously with chemical analysis via mass spectrometry. Multidimensional chromatography was used to isolate and identify chemicals with high-characteristic swine odor. The effects of sampling time, distance from a source, and the presence of PM on the abundance of specific gases, odor intensity, and odor character were tested. Steel plates were effectively able to collect key volatile compounds and odorants. The abundance of specific gases and odor was amplified when plates collected PM. The results of this research indicate that PM is major carrier of odor and several key swine odorants. Three odor panelists were consistent in identifying p-cresol as closely resembling characteristic swine odor, as well as attributing to p-cresol the largest odor response out of the samples. Further research is warranted to determine how the control of PM emissions from swine housing could affect odor emissions.

Metabolism of linalool and substrate analogs in grape berry mesocarp of Vitis vinifera L. cv. Morio Muscat: demonstration of stereoselective oxygenation and glycosylation

The oxidative metabolism of linalool in Vitis vinifera L. cv. Morio Muscat has been investigated by in vivo feeding experiments using the regioselectively stable isotope-labelled substrates d 5-(3 R/ S)-linalool, d 6-(3 R)-linalool, d 2, 18O-(3 R/ S)-linalool and the substrate analog (3 R)-linalyl methyl ether. The enantiomeric and diastereoisomeric ratios of the metabolites were determined by means of enantioselective multidimensional gas chromatography–mass spectrometry. Stereoselective transformation to diendiol II and the furanoid and pyranoid linalool oxides could be demonstrated. Other metabolites like diendiol I, hotrienol and 8-hydroxy linalool were detectable as well. The studies indicate that the corresponding metabolites were efficiently glycoconjugated. Time course studies including the determination of conversion rates revealed that the activity of these secondary transformations is dependent on the ripening stage. The mass spectrometric analysis of the labelled linalool oxides derived from mixed labelled d 2, 18O-linalool and the stereoselective anaylsis of the metabolite 6-methoxy-2,6-dimethyloct-7-en-2,3-diol, which is derived from the substrate analog (3 R)-linalyl methyl ether, give evidence that the furanoid linalool oxides are generated via two different reaction pathways.

Propylene Glycol Vapor Contamination in Controlled Environment Growth Chambers: Toxicity to Corn and Soybean Plants

A major, often unrecognized variable regulating plant growth in semi-closed environment is air contaminant. The vapor of propylene glycol (PG), which was used as coolant in growth chambers, has been found to be toxic to corn (Zea mays L.) and soybean (Glycine maxL.) plants. PG solution leaked from a valve packing system and volatilized to vapor, which was trapped in a semi-closed growth chamber. Symptoms of leaf edge chlorosis, later developing into necrosis, were observed on the third day of emergence or on the third day after moving healthy plants into the chamber. For young soybean plants, symptoms were slightly different from those observed in corn plants; the chlorosis symptoms were not uniformly distributed on all leaves. Some soybean leaves curled up and others had white spots. This problem was identified by using a portable photoionization detector to obtain instantaneous readings of total volatile organic compound concentrations inside the chambers. The presence of PG in selected chambers was verified using sample collection with solid phase microextraction (SPME) followed by analysis with multi-dimensional gas chromatography mass spectrometry (MD-GC-MS). This information is pertinent to researchers who use controlled environment to grow plants.

Biosynthesis of mono- and sesquiterpenes in carrot roots and leaves ( Daucus carota L.): metabolic cross talk of cytosolic mevalonate and plastidial methylerythritol phosphate pathways

The biosynthesis of the monoterpenes terpinolene and myrcene and the sesquiterpene β-caryophyllene in roots and leaves of two carrot varieties ( Daucus carota L. cultivars Bolero and Kazan) were investigated by in vivo feeding experiments with [5,5- 2H 2]-mevalonic acid lactone (d 2-MVL) and [5,5- 2H 2]-1-deoxy- d-xylulose (d 2-DOX). The volatiles of the tissues were extracted by stir bar sorptive extraction and analyzed using thermal desorption–multidimensional gas chromatography–mass spectrometry. The experiments demonstrate independent de novo-biosynthesis of terpenoids in carrot roots and in carrot leaves. In both plant tissues monoterpenes are biosynthesized exclusively via the 1-deoxy- d-xylulose/2-C-methyl- d-erythritol-4-phosphate (DOXP/MEP) pathway, whereas sesquiterpenes are generated by the classical mevalonic acid pathway as well as by the DOXP/MEP route. A more detailed investigation of carrot root tissues revealed that the biosynthesis of terpenes is mainly localized in the phloem. Nevertheless, in xylem a de novo-biosynthesis of terpenes was detectable as well, even in the absence of oil ducts in this tissue.

Biogenetic studies in Syringa vulgaris L.: bioconversion of (18)O(2H)-labeled precursors into lilac aldehydes and lilac alcohols.

Syringa vulgaris L. inflorescences, petals, and chloroplasts, isolated from lilac flower petals, were fed with aqueous solutions of (18)O-labeled linalool and [5,5-(2)H(2)]-deoxy-d-xylose (DOX). The chloroplasts of lilac flower petals were isolated after feeding experiments with labeled precursors. Volatiles from the chloroplasts were extracted by stir bar sorptive extraction (SBSE) and analyzed using enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS). Feeding experiments with DOX indicate that the novel mevalonate-independent 1-deoxy-d-xylose 5-phosphate/2C-methyl-d-erythritol 4-phosphate (DOX/MEP) is the decisive pathway of lilac aldehyde and lilac alcohol, respectively. Bioconversion of [(18)O]linalool into lilac aldehyde and lilac alcohol during in vivo feeding experiments was monitored, and the metabolic pathways are discussed.

Stereoselective analysis of 2-hydroxysebacic acid in urine of patients with Zellweger syndrome and of premature infants fed with medium-chain triglycerides.

The chiral metabolite 2-hydroxysebacic acid (2-HS) is considered to be an important diagnostic marker for peroxisomal disorders. The pathway of formation of 2-HS, excreted in increased amounts in patients with peroxisomal diseases, is not absolutely clear. Moreover, there is no information about the enantiomeric distribution of 2-HS in human urine. Here, we describe the stereodifferentiation of 2-HS in urine samples of nine patients with Zellweger syndrome (ZS), and for the first time in urine samples of premature infants fed a medium-chain triglyceride (MCT)-containing diet. Using enantioselective multidimensional gas chromatography-mass spectrometry, an increased excretion of 2R-HS was observed in all investigated ZS patients. 2-HS was also present in urine samples of premature infants fed MCT. Analogously to the ZS patients, a dominant 2R-HS excretion in the urine samples of the premature infants was identified. The formation of 2-HS is expected to result from the same or similar pathways as described for ZS patients. Additionally, we determined the absolute configuration of urinary 3-hydroxysebacic acid (3-HS) in the cases investigated. The enantioselective analysis provides further information for the diagnosis and treatment of patients with impaired peroxisomal fatty acid oxidation. Further insight into the metabolic origin and the biochemical pathway leading to these urinary metabolites is provided.

Multidimensional gas chromatography–mass spectrometry for tracer studies of fatty acid metabolism via stable isotopes in cultured human trophoblast cells

The determination of placental fatty acid metabolism using stable isotope-labeled tracers was investigated in the human placental choriocarcinoma (JAR) cell line. Stable isotope incorporation was measured by MDGC–MS. The cultured trophoblast cells incorporated and metabolized the essential fatty acids to long-chain polyunsaturated fatty acids. The described method enables the detection of a low Δ 6-desaturase activity in this human placental cell line. The developed MDGC–MS method allows the assessment of long-chain polyunsaturated fatty acid biosynthesis in cultured cells with high sensitivity and selectivity. In this respect, tracer studies with MDGC–MS will be a powerful tool to clarify the significance of placental fatty acid metabolism.

Supplies, policy, economics, forecasts

Identification and quantification of related-structure impurity is a research focus in the purity assessment of organic compounds. Determination of the purity value and uncertainty assessment are also important in the metrological research. A method for the determination of related-structure impurity in pure aldrin sample has been developed by using heart-cut multi-dimensional gas chromatography–mass spectrometry (MDGC/MS). Compared to the traditional one-dimensional (1-D) GC system, the two separated columns in the MDGC/MS system can effectively reduce co-elution, enhance separation capability, and thus improve detectability of the trace-level impurities. In addition, MDGC/MS system was simultaneously equipped with flame ionization detector (FID) or electron capture detector (ECD) in the first GC unit and mass spectrometry (MS) detector in the second GC unit. Therefore, accurate quantitative results of the trace-level impurities can be easily achieved by isolation of principal component to the second dimension column using “heart-cut” process. The mass fraction of related-structure impurities in aldrin samples obtained using MDGC/MS system ranged from 6.8 × 10−3 mg g−1 to 26.47 mg g−1 with five orders of magnitude, which is hard to be realized by mean of the 1-D GC. Excellent linearity with correlation coefficients of above 0.999 was achieved for each impurity analysis over a wide range of concentrations. Limits of quantification (LOQ) varied from 250 ng g−1 to 330 ng g−1 for FID, and from 1.0 ng g−1 to 2.0 ng g−1 detected by ECD. The combined standard uncertainty (uc) was lower than 0.37 mg g−1 and 0.040 mg g−1 detected using FID and ECD, respectively. Therefore, performance characterization of MDGC/MS used in the study is fit for quantification analysis of trace-level impurity. These results demonstrate that the MDGC/MS is extremely suitable for the purity assessment of organic compounds with medium structural complexity and low polarity.

Analysis of ethyl carbamate in wines using solid-phase extraction and multidimensional gas chromatography/mass spectrometry.

The method describes a rapid and accurate procedure for the analysis of ethyl carbamate in wines. The separation of the ethyl carbamate (EC), the target analyte, from alcohol and the sample matrix is a challenge to many analytical chemists. After alcohol removal from the sample, EC was extracted and concentrated by solid-phase extraction. For analysis of EC, large-volume injection on a programmable temperature vaporization (PTV) inlet was used followed by multidimensional gas chromatography/mass spectrometry (MDGC/MS) using electron-impact ionization (EI). For quantitation, the ratio of ions produced during EI at m/z 62 (EC) and 64 (isotopically labeled EC) was monitored. The use of solid-phase extraction and MDGC/MS removes the majority of the matrix interference encountered in other methods. A linear dynamic range was established from 0.387 to 1160 ng/mL, with a limit of detection at 0.1 ng/mL and limit of quantitation at 1 ng/mL.

Authenticity assessment of lavender oils using GC-P-IRMS: 2 H/ 1 H isotope ratios of linalool and linalyl acetate

Gas chromatography-pyrolysis-isotope mass spectrometry (GC-P-IRMS) is applied to the authenticity assessment of lavender oils. For this reason, self-prepared lavender oils, samples of linalool and linalyl acetate labeled as synthetic and natural, and commercially available lavender oils have been investigated. 2H/1H isotope ratios of linalool and linalyl acetate have been determined, and characteristic ranges of authenticity were deduced. Samples of natural linalool and linalyl acetate are clearly differentiated from those of synthetic origin by their δ2HV-SMOW values. Besides enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS), online GC-P-IRMS has proven to be an additional and powerful tool in the detection of lavender oils adulteration.