Gas Chromatography-ion Trap Research Articles

Validation of an analytical method for analysis of cannabinoids in hair by headspace solid-phase microextraction and gas chromatography–ion trap tandem mass spectrometry

The development of an analytical method for the determination of Δ 9-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) in samples of human hair is described. Samples were subjected to a procedure based on the combination of headspace solid-phase microextraction (HS-SPME) with gas chromatography linked with mass spectrometry operating in tandem mode (GC–MS/MS). A 10 mg aliquot of sample was firstly decontaminated using petroleum ether, deionized water and dichloromethane (2 mL of each solvent), for 10 min under sonication, and then digested in alkaline solution (1 mol L −1 NaOH). The method variables evaluated were pH, mass of hair, fiber type, extraction temperature, desorption time, ionic strength, pre-equilibrium time and extraction time. Parameters concerning operation of the tandem mode MS/MS were also assessed and optimized. Validation of the method demonstrated excellent linearity in the range 0.1–8.0 ng mg −1, with regression coefficients better than 0.994. Precision was determined using two different concentrations (upper and lower limits of the linear range), and RSD values were between 6.6 and 16.4%. Absolute recoveries (measured in triplicate) were in the range 1.1–8.7%, and limits of detection and quantification were 0.007–0.031 ng mg −1 and 0.012–0.062 ng mg −1, respectively. The LOQ for THC (0.062 ng mg −1) was below the cut-off value (LOQ ≤ 0.1 ng mg −1) established by the Society of Hair Testing (SOHT), the Society of Toxicological and Forensic Chemistry (STFCh) and the Société Française de Toxicologie Analytique (SFTA). The optimized SPME method was applied in analysis of hair samples from Cannabis drug users, showing that CBN and CBD were present in all samples analyzed.

Pressurised hot water extraction followed by simultaneous derivatization and headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry for the determination of aliphatic primary amines in sewage sludge

In this paper we describe an environmentally friendly and sensitive method for the determination of ten primary amines in sewage sludge. The method is based on pressurised hot water extraction (PHWE) followed by simultaneous derivatization with pentafluorobenzaldehyde (PFBAY) and headspace solid-phase microextraction (HS-SPME) and subsequent gas-chromatography ion-trap tandem mass spectrometry (GC-IT-MS–MS) analysis. The influence of the main factors on the PHWE of sludge was optimized by a central composite design. For all species the optimal conditions were water at pH 4 as the extracting solvent, an extraction temperature of 100 °C and an extraction time of 15 min. The separation and detection of the ten amines by GC-IT-MS–MS took just 10 min and the entire process took approximately 1 h. Repeatability and reproducibility between days, expressed as RSD (%) ( n = 5), were less than 19 and 24%, respectively. The average limit of detection (LOD) was of 65 μg kg −1 s (range found 9–135) and the average limit of quantification (LOQ) was of 230 μg kg −1 (range found 50–450) of dry weight (d.w.). Under optimized conditions we used this method to determine the compounds in industrial and municipal sewage sludge samples and in sludge from a potable water treatment plant. Methylamine and isobutylamine showed the highest levels in one of the industrial sewage sludge samples (404 and 543 mg kg −1 (d.w.), respectively). To our knowledge, this paper presents for the first time the determination of ten primary amines in sewage sludge samples using PHWE.

Development and validation of a GC/IT-MS method for simultaneous quantitation of para and meta-synephrine in biological samples

After the FDA's ban of ephedrine-containing supplements, Citrus aurantium appeared as an alternative to ephedra in herbal weight loss products. Synephrine, the most abundant active component of C. aurantium, exists in three different structural or positional isomeric forms (ortho-o-, meta-m-, and para-p-). Dietary supplements contain m- and p-synephrine, both alpha-adrenergic agonists,while the m-isoform is the most potent at alpha(1)-adrenoreceptors. In spite of the pharmacokinetic and toxicological interest in the study of these compounds, adequate methods for their quantification in biological samples are yet to be developed. Thus, in the present study, a sensitive gas chromatography-ion trap mass spectrometry (GC/IT-MS) method was developed and validated for the simultaneous quantitation of m- and p-synephrine in a cellular matrix after solid phase extraction (SPE). The validation of the method was performed through the evaluation of the following parameters: selectivity, linearity, specificity, precision, accuracy, limit of detection, limit of quantification, and recovery. The method's applicability was studied in two different biological matrices by evaluating p- and m-synephrine uptake in Caco-2 cells and also in freshly isolated cardiomyocytes from adult rat. The developed GC/IT-MS method was shown to be selective, accurate, precise, and valid for simultaneous determination of p- and m-synephrine in biological samples.

Gas chromatography–ion trap mass spectrometry method for the simultaneous measurement of MDMA (ecstasy) and its metabolites, MDA, HMA, and HMMA in plasma and urine

The investigation of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) abuse requires very robust methods with high sensitivity and wide linearity ranges for the quantification of this drug of abuse and its main metabolites in body fluids. An optimized gas chromatography–ion trap mass spectrometry (GC–IT/MS) methodology with electron impact ionization addressing these issues is presented. The sample preparation involves an enzymatic hydrolysis of urine and plasma for conjugate cleavage, a SPE extraction, and a derivatization process. The method was fully validated in rat plasma and urine. Linearity for a wide concentration range was achieved for MDMA, and the metabolites 3,4-methylenedioxyamphetamine (MDA), 4-hydroxy-3-methoxyamphetamine (HMA) and 4-hydroxy-3-methoxymethamphetamine (HMMA). Limits of quantification were 2 ng/mL in plasma and 3.5 ng/mL in urine using a Selected Ion Monitoring detection mode. Selectivity, accuracy, precision, and recovery met the required criteria for the method validation. This GC–IT/MS method provides high sensitivity and adequate performance characteristics for the simultaneous quantification of MDMA, MDA, HMA and HMMA in the studied matrices.

Investigation of reagent gases for the positive chemical ionization of select polybrominated diphenyl ethers

Abstract Polybrominated diphenyl ethers (PBDEs) fall into the class of compounds known as brominated flame retardants and their incorporation in a multitude of products is responsible for saving numerous lives. However, toxicology studies have alerted researchers to the potential adverse health effects that may develop as a result of prolonged or extreme exposure to these compounds. Frequent disposal and subsequent leaching has focused concern on environmental concentrations and current reports cite increasing levels. Method development continues in support of this research and the present work examines the feasibility of utilizing gas chromatography ion trap mass spectrometry operating in positive ion chemical ionization mode. In the evaluation of reagents for chemical ionization (methane, methanol and acetonitrile), comparative results of all three reagents demonstrated more difficult protonation as the number of bromine atoms increased. Methane, possessing the lowest proton affinity, provided the highest response for the analytes. Further, when methane chemical ionization was compared to electron impact ionization, the tetra-congener showed approximately 8× greater sensitivity and the penta- and hexa-congeners demonstrated approximately 2× greater. CI parameters, such as ionization and reaction times, were optimized to provide the highest analyte response and this was followed by the investigation of the employment of MS n . In the this mode, optimal excitation amplitude delivered sufficient fragmentation while maintaining maximum signal, yielding final instrument detection limits in the sub µg L − 1 range.

SAFFRON AS ENVIRONMENTAL BIOMARKER OF DIFFUSE CONTAMINATION

For the first time saffron has been employed as environmental bioindicator to characterize the presence of a complex polycyclic aromatic hydrocarbons (PAHs) mixture. The objective of this study was to provide quantitative information regarding PAHs contamination in saffron in order to verify the possibility to use this spice as environmental biomarker and to determine the bioaccumulation of these compounds. 27 saffron samples coming from different countries were analyzed by stir bar sorptive extraction technique in combination with gas chromatography-ion trap tandem mass spectrometry. The data show that the samples contained different levels of contaminants but some of them have higher concentrations than the maximum residue limits (MRLs) of pollutants established by the European Commission for spices. 9 out of 27 saffron samples contained benzo[a]pyrene in a range between 10.5 and 18.5 μg/kg values higher than the MRL.

Multiresidue Analysis of 50 Pesticides in Grape, Pomegranate, and Mango by Gas Chromatography−Ion Trap Mass Spectrometry

A selective and sensitive multiresidue analysis method is reported for simultaneous determination of 50 pesticides of different chemical classes in three commercially important fruits of different nature viz. grape, pomegranate, and mango. The sample preparation method involves extraction of a 10 g sample with 10 mL of ethyl acetate; cleanup by dispersive solid phase extraction with primary secondary amine (PSA, 25 mg) for grape and PSA + graphitized carbon black (25 + 5 mg) for pomegranate and mango; and determination by gas chromatography-ion trap mass spectrometry through multiple reaction monitoring (MRM). Sample preparation under acidified (pH 4) and cold (<4 degrees C) conditions, use of PTV-large volume injection (20 microL) through multibaffled liner and chromatographic separation on a short 10 m VF-5MS capillary column gave a satisfactory response for all of the analytes including relatively unstable compounds such as captan, captafol, folpet, endrine, and iprodione within 31.8 min. The limit of quantification (LOQ) of most of the compounds was <or=10 ng g(-1) except for captan, captafol, and folpet, where the LOQ was <or=20 ng g(-1). For each analyte, the unique and most abundant MRM was selected for quantification, and the next most abundant for confirmation, with their abundance ratio being used for unambiguous identification of any detected pesticide in samples within 20% tolerance range at the LOQ level. Use of matrix-matched standards could minimize the matrix effect, which was lowest in grape, followed by pomegranate and mango. Recoveries ranged within 70-120% at 10, 20, and 50 ng g(-1) in all three matrixes with associated relative standard deviations <20% (n = 6). The method could be successfully applied to the screening of 100 farm samples for compliance to EU maximum residue limits.

Traceability of olive oil based on volatiles pattern and multivariate analysis

An automated head-space solid-phase microextraction (HS-SPME)-based sampling procedure, coupled to gas chromatography–ion trap mass spectrometry (GC–ITMS), was developed and employed for fast characterisation of olive oil volatiles. In total, 914 samples were collected, over three production seasons, in north-western Italy—Liguria ( n = 210) and other regions—in addition to the rest of Italy, Spain, France, Greece, Cyprus, and Turkey ( n = 704) with the aim to distinguish, based on analytical (profiling) data, the olive oils labelled as “Ligurian” (protected denomination of origin region, PDO) from all the others (“non-Ligurian”). For the chemometric analysis, linear discriminant analysis (LDA) and artificial neural networks with multilayer perceptrons (ANN-MLP) were tested. Employing LDA, somewhat lower recognition (81.4%) and prediction (61.7%) abilities were obtained. The classification model was significantly improved using ANN-MLP. Under these conditions, the recognition (90.1%) and prediction (81.1%) abilities were achieved. The diagnostic value of the data obtained by one-dimensional GC–ITMS were compared with those generated by two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOFMS), allowing a comprehensive analysis of olive oil volatiles.

Determination of pyrethroid insecticides in sediment by gas chromatography—Ion trap tandem mass spectrometry

A method was developed to analyze 10 pyrethroid insecticides in sediment by gas chromatography-ion trap tandem mass spectrometry (GC-MS/MS) after accelerated solvent extraction and solid phase extraction cleanup. The MS/MS parameters included selection of the precursor and product ions, excitation mode, excitation amplitude and the stability parameter q(z), and were optimized to maximize detection sensitivity. Due to its superior ability to remove background noise, GC-MS/MS showed elevated selectivity and improved confidence in peak identification compared to GC-electron capture detector (ECD). The instrumental detection limits for GC-MS/MS ranged from 148 to 4033 fg, and the calibration curves were linear from 5 to 1000 microg/L for all of the pyrethroids except cyfluthrin. The method detection limits for pyrethroids ranged from 0.10 to 0.80 microg/kg dry sediment, while the recoveries were 59.7-128%, 60.6-90.9% and 63.2-83.6% with the relative standard deviations of 5.3-25.3%, 1.1-10.6% and 3.0-15.6% at the spiking levels of 1, 5 and 20 microg/kg, respectively. Field sediment collected from California was used to validate the newly developed method, and analytical results were comparable to those by GC-ECD in most cases. However, as the result of a cleaner background, more pyrethroids were identified by GC-MS/MS.

The dissipation rates of myclobutanil and residue analysis in wheat and soil using gas chromatography-ion trap mass spectrometry

The dissipation of myclobutanil (triazole fungicide) in wheat plant, grain and soil under the local weather and soil conditions was studied and fungicide residues were determined by GC-ITMS. Myclobutanil (25% EC) was applied at two dosages, 60 g a.i. ha−1 (recommended) and 120 g a.i. ha−1 (2 times of the recommended dosage) in the experimental fields in Shandong, Beijing and Henan provinces (experimental localities). The detection limit (LOD) and the limit of quantification (LOQ) of myclobutanil were 0.6 µg kg−1 and 2 µg kg−1 respectively, and they were much below the maximum residue limit (MRL 0.02 mg kg−1) in the EU. The average recoveries were 76.4–97.7, 82.6–92.6 and 75.0–94.4% with relative standard deviation (RSD) of 6.3–15.9, 3.8–17.3 and 3.0–19.7% in wheat plant at four spiking levels (0.01, 0.1, 0.5, 10 mg kg−1), wheat grain at four spiking levels (0.005, 0.01, 0.1, 10 mg kg−1) and soil at five spiking levels (0.002, 0.01, 0.1, 0.5, 10 mg kg−1), respectively. The results showed that the half-lives of myclobutanil in wheat plant and soil from Shandong, Beijing and Henan were 3.5–4.5 and 11.0–11.7 days, respectively. At harvest, wheat grain samples were found to contain myclobutanil well below the MRL following the recommended dosage and the interval of 20 days after last application.

Tissue Distribution of Polychlorinated Biphenyls and Organochlorine Pesticides and Potential Toxicity to Alaskan Northern Fur Seals Assessed Using PCBs Congener Specific Mode of Action Schemes

The fur seal (Callorhinus ursinus) population has decreased in their primary breeding grounds in the Bering Sea; contamination is among suspected causes. Our goal was to better understand the extent of contamination of seal tissues with certain organochlorine compounds by measuring the concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fur seal tissues from St. Paul Island, to gain a better perspective of tissue congener distribution and to evaluate the observed PCB levels against toxicologically significant levels for modes of action. Concentrations of 145 PCB congeners (Sigma(145)PCBs) and 12 OCPs were measured with gas chromatography-ion trap mass spectrometry in 8 different tissues of 10 male northern fur seals. The mean concentrations of SigmaOCPs [in ng/g lipid weight (lw)] were 1180 in blubber, 985 in the heart, 1007 in the liver, 817 in the kidney, 941 in muscle, 660 in reproductive tissues, 204 in the brain, and 322 in the lung. The mean concentrations of Sigma(145)PCBs (in ng/g lw) were 823 in blubber, 777 in the liver, 732 in the heart, 646 in reproductive tissues, 638 in muscle, 587 in the kidney, 128 in the lung, and 74.3 in brain tissues. Concentrations of PCBs affecting the aryl hydrocarbon receptor expressed as total PCB toxic equivalents (SigmaPCB-TEQs) ranged from 0.3 to 545 pg/g lw for the various tissues. The major contributors to SigmaPCB-TEQs are CB-118 in muscle, brain, lung, kidney, and liver, CB-126 in blubber, and CB-118 and CB-126 equally in the heart and reproductive tissues. Concentrations of PCBs affecting Ca(2+) homeostatsis expressed as the neurotoxic equivalent (NEQ) showed SigmaPCB-NEQs ranged from 17.7 to 215 ng/g lw in all tissues. Although no composite measure of perturbation of thyroid function is available, sufficient amounts of congeners with high binding to the thyroxine transport system were present to warrant consideration of this mode of action in future studies. Analyses of 145 PCBs and mode of action evaluation suggest that PCB contamination could potentially exert an effect on the Alaskan northern fur seal population although the PCB concentrations have been decreasing in the fur seals over the last decade.

Postmortem Analyses Unveil the Poor Efficacy of Decontamination, Anti-Inflammatory and Immunosuppressive Therapies in Paraquat Human Intoxications

BackgroundFatalities resulting from paraquat (PQ) self-poisonings represent a major burden of this herbicide. Specific therapeutic approaches have been followed to interrupt its toxic pathway, namely decontamination measures to prevent PQ absorption and to increase its excretion from organism, as well as the administration of anti-inflammatory and immunosuppressive drugs. Until now, none of the postmortem studies resulting from human PQ poisonings have assessed the relationship of these therapeutic measures with PQ toxicokinetics and related histopathological lesions, these being the aims of the present study.Methodology/Principal FindingsFor that purpose, during 2008, we collected human fluids and tissues from five forensic autopsies following fatal PQ poisonings. PQ levels were measured by gas chromatography-ion trap mass spectrometry. Structural inflammatory lesions were evaluated by histological and immunohistochemistry analysis. The samples of cardiac blood, urine, gastric and duodenal wall, liver, lung, kidney, heart and diaphragm, showed quantifiable levels of PQ even at 6 days post-intoxication. Structural analysis showed diffused necrotic areas, intense macrophage activation and leukocyte infiltration in all analyzed tissues. By immunohistochemistry it was possible to observe a strong nuclear factor kappa-B (NF-κB) activation and excessive collagen deposition.Conclusions/SignificanceConsidering the observed PQ levels in all analyzed tissues and the expressive inflammatory reaction that ultimately leads to fibrosis, we conclude that the therapeutic protocol usually performed needs to be reviewed, in order to increase the efficacy of PQ elimination from the body as well as to diminish the inflammatory process.

Rapid and sensitive gas chromatography–ion-trap tandem mass spectrometry method for the determination of tobacco-specific N-nitrosamines in secondhand smoke

Tobacco-specific nitrosamines (TSNAs) are some of the most potent carcinogens in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risks. We developed and validated a specific and sensitive method to measure four TSNAs adsorbed to model surfaces and secondhand smoke (SHS) particles using gas chromatography–ion-trap tandem mass spectrometry. In an 18-m 3 room-sized chamber, a smoking machine generated realistic concentrations of SHS that were actively sampled on Teflon-coated fiber glass (TCFG) filters, and passively sampled on cellulose substrates. A simple solid–liquid extraction protocol using methanol as solvent was successfully applied to both substrates with recoveries ranging from 85 to 115%. For each TSNA, tandem MS parameters were optimized and the major fragmentation pathways were elucidated. The method showed excellent performance, with a linear dynamic range from 2 to 1000 ng mL −1, low detection limits (S/N > 3) of 30–300 pg mL −1 and precision with experimental errors below 10% for all compounds. Moreover, no interfering peaks were observed, indicating a high selectivity of MS/MS without the need for a sample clean-up step. This method provides a suitable analytical tool to detect and quantify traces of TSNA in indoor environments polluted with SHS.

Selective pressurized liquid extraction of polybrominated diphenyl ethers in fish

A fast and simple method for the analysis of polybrominated diphenyl ethers (PBDEs) in fish samples was developed using a one-step extraction and clean-up by means of pressurized liquid extraction (PLE) combined with gas chromatography–ion trap tandem mass spectrometry (GC–ITMS–MS). The selective PLE method provided to obtain ready-to-analyse extracts without any additional clean-up step, using a sorbent as fat retainer inside the PLE cell. Several PLE operating conditions, such as solvent type, extraction temperature and time, number of cycles and type of fat retainer, were studied. Using Florisil as fat retainer, maximum recoveries of PBDEs (83–108%) with minimum presence of matrix-interfering compounds were obtained using a mixture of n-hexane:dichloromethane 90:10 (v/v) as solvent, an extraction temperature of 100 °C and a static extraction time of 5 min in combination with three static cycles. Quality parameters of the method were established using standards and fish samples. Limits of detection and quantification ranged from 10 to 34 pg g −1 wet weight and between 34 and 68 pg g −1 wet weight, respectively. In addition, good linearity (between 1 and 500 ng ml −1) and high precision (RSD % < 15%) were achieved. The method was validated using the standard reference material SRM-1945 (whale blubber) and was then applied to the analysis of PBDEs in fish samples.

Indoor Air Quality Assessment of Elementary Schools in Curitiba, Brazil

The promotion of good indoor air quality in schools is of particular public concern for two main reasons: (1) school-age children spend at least 30% of their time inside classrooms and (2) indoor air quality in urban areas is substantially influenced by the outdoor pollutants, exposing tenants to potentially toxic substances. Two schools in Curitiba, Brazil, were selected to characterize the gaseous compounds indoor and outdoor of the classrooms. The concentrations of benzene, toluene, ethylbenzene, and the isomers xylenes (BTEX); NO2; SO2; O3; acetic acid (HAc); and formic acid (HFor) were assessed using passive diffusion tubes. BTEX were analyzed by gas chromatography–ion trap mass spectrometry and other collected gasses by ion chromatography. The concentration of NO2 varied between 9.5 and 23 µg m−3, whereas SO2 showed an interval from 0.1 to 4.8 µg m−3. Within the schools, BTEX concentrations were predominant. Formic and acetic acids inside the classrooms revealed intermediate concentrations of 1.5 µg m−3 and 1.2 µg m−3, respectively.

Multiresidue determination of 11 new fungicides in grapes and wines by liquid–liquid extraction/clean-up and programmable temperature vaporization injection with analyte protectants/gas chromatography/ion trap mass spectrometry

A gas chromatographic ion trap mass spectrometry (GC-ITMS) method was developed for the determination of 11 new generation fungicides (benalaxyl, benalaxyl-M, boscalid, cyazofamid, famoxadone, fenamidone, fluquinconazole, iprovalicarb, pyraclostrobin, trifloxystrobin and zoxamide) in grapes and wines. Samples were extracted with ethyl acetate:hexane (1:1, v/v) and cleaned-up with graphitized carbon black/primary secondary amine (GCB/PSA) solid-phase extraction (SPE) cartridges using acetonitrile:toluene (3:1, v/v) as eluent. The addition of analyte protectants (3-ethoxy-1,2-propanediol, d-sorbitol and l-gulonic acid γ-lactone) in the final extracts allowed to avoid the matrix-induced response enhancement effect on quantitation process with absolute recoveries ca. 100%. Precision (expressed as relative standard deviation) was lower than 16% for all fungicides. Limits of detection and quantitation were lower than 0.01 mg/kg or mg/L, except for cyazofamid, much smaller in all cases than maximum residue levels (MRLs) established by European Union for grapes and by Switzerland and Italy for wines. The proposed method was applied to determine fungicide residues in three different white grapes for vinification produced in Ribeiro area in Galicia (NW Spain), as well as in their corresponding final wines.

Quantitative determination and characterisation of the main odourants of Mencía monovarietal red wines

Abstract This study focus on the development of a headspace solid-phase microextraction (HS-SPME) method coupled to gas chromatography–ion trap mass spectrometry (GC–ITMS) to identify and quantify simultaneously 32 characteristic volatile compounds. A mixed level factorial 3 × 2 3 design was performed to asses the influence of several factors and their interactions (extraction temperature, fibre coating, salt addition and sample volume) on the extraction efficiency. The evaluation of the design showed that temperature and fibre coating were the most significant variables. The method showed good linearity ( r 2 > 0.990) and repeatability (RSD ⩽ 16%) for all compounds, with detection limits ranging from 0.0024 μg/L for limonene to 238 μg/L for ethyl 3-hydroxybutyrate, in general below their odour threshold limits. Matrix effects were thoroughly studied. The method was after applied to the first aroma characterisation of the monovarietal young red wine Mencia from the Galician (NW Spain) designation of origin “Valdeorras DO”. To achieve the identification of the major would-be impact odourants, the odour activity value (OAV) was also calculated.

Analysis of permethrin isomers in composite diet samples by molecularly imprinted solid-phase extraction and isotope dilution gas chromatography–ion trap mass spectrometry

Determination of an individual's aggregate dietary ingestion of pesticides entails analysis of a difficult sample matrix. Permethrin-specific molecularly imprinted polymer (MIP) solid-phase extraction cartridges were developed for use as a sample preparation technique for a composite food matrix. Vortexing with acetonitrile and centrifugation were found to provide optimal extraction of the permethrin isomers from the composite foods. The acetonitrile (with 1% acetic acid) was mostly evaporated and the analytes reconstituted in 90:10 water/acetonitrile in preparation for molecularly imprinted solid-phase extraction. Permethrin elution was accomplished with acetonitrile and sample extracts were analyzed by isotope dilution gas chromatography–ion trap mass spectrometry. Quantitation of product ions provided definitive identification of the pesticide isomers. The final method parameters were tested with fortified composite food samples of varying fat content (1%, 5%, and 10%) and recoveries ranged from 99.3% to 126%. Vegetable samples with incurred pesticide levels were also analyzed with the given method and recoveries were acceptable (81.0–95.7%). Method detection limits were demonstrated in the low ppb range. Finally, the applicability of the MIP stationary phase to extract other pyrethroids, specifically cyfluthrin and cypermethrin, was also investigated.

Alternative GC–MS approaches in the analysis of substituted pyrazines and other volatile aromatic compounds formed during Maillard reaction in potato chips

Several methods have been developed for the analysis of substituted pyrazines and related substances in potato chips. Following separation/detection approaches (all employing head-space solid phase microextraction, HS-SPME, for volatiles sampling), have been critically assessed in our study: (i) gas chromatography–ion trap mass spectrometry (GC–ITMS), (ii) gas chromatography–time-of-flight mass spectrometry (GC–TOFMS); (iii) comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOFMS). Although in none of the tested systems full chromatographic resolution of some isomeric pairs could be achieved, the use of GC × GC–TOFMS offered the best solution, mainly because of distinctly lower limits of quantification (LOQs) for all of 13 target alkylpyrazines. In addition to good performance characteristics, a non-target screening and tentative identification of altogether 46 N-containing heterocyclic compounds (pyrazines, pyrrols, pyridines, pyrrolidinones, and tetrahydropyridines) was also enabled.

Antimicrobial activity in the vapour phase of a combination of cinnamon and clove essential oils

The antimicrobial activity of the vapour generated by a combination of cinnamon and clove essential oils against the growth of four Gram-negative (Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruoginosa and Salmonella choleraesuis) and four Gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus and Enterococcus faecalis) was assessed by means of the fractional inhibitory concentration index (FIC) of the mixture. The presence of synergism or antagonism effects depended on the reference parameter used to estimate such an index. If the minimal inhibitory concentrations were applied, the vapours of the combination of essential oils exerted an antagonistic effect on the growth of E. coli, while they wielded a synergistic effect for the inhibition of L. monocytogenes, B. cereus and Y. enterocolitica when the concentrations of maximal inhibition were used. This fact revealed a clear concentration-dependent interaction. The headspace of the cinnamon and clove essential oils and their combination was sampled by solid-phase microextraction (SPME) and the constituents identified and quantified by gas chromatography–ion trap mass spectrometry (GC/ITMS). Eugenol was the most abundant compound for the three antibacterial atmospheres. The differences in behaviour could be attributed to minor compounds. The combined headspace contained slightly larger amounts of 1,8-cineole and camphor, which are believed to enhance the eugenol activity. The mechanisms responsible for the antagonism are, however, less known and much further investigation is required. To the best of our knowledge this is the first time a combination of essential oils in the vapour phase has been tested as a preservative method to prevent microorganism proliferation.