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When working with humid gaseous samples, the amount of water vapour collected in a needle trap along with volatile analytes may vary from sample to sample and decrease during the storage. This has a major impact on desorption efficiency and recovery. We propose the addition of a labelled internal standards to nullify the effect of variable humidity on the analytical performance of needle trap micro-extraction combined with gas chromatography mass spectrometry. Triple-bed (Divinylbenzene/Carbopack X/Carboxen 1000) and single-bed (Tenax GR) needles were tested with standard gaseous mixtures prepared at different relative humidity levels (85%, 50% and 10%). The standard mixtures contained twenty-five analytes representative of breath and ambient air constituents, including hydrocarbons, ketones, aldehydes, aromatics, and sulphurs, in the concentration range 0.1-700 ppbv. The two needles showed different behaviours, as recovery was independent of humidity for single-beds, whereas a low recovery (10-20%) was observed when triple-beds trapped very volatile compounds at low humidity (e.g. pentane and ethanol, 10% relative humidity. Triple-beds showed an almost quantitative recovery (>90%) of all the analytes at 50% and 85% relative humidity. This big difference was probably due to the reduced action of water vapour pressure during the desorption step. The addition of 6 D-acetone and 8 D-toluene to the sorbent material before gas sampling and the normalization of raw data nullified this effect, thereby lowering the variations of analyte recovery at different humidity levels down to 20%. Internal standards were also exploited to limit within 10-20% alterations in peak areas of very volatile compounds during needle storage at room temperature. This variation may results from a loss of water vapour either retained from the sorbent material and/or condensed on triple-bed needle walls. After normalization, the inter- and intra-day precision were halved to 5% and 10% in the case of single-beds, respectively, and to 15% and 20% with three-beds. The addition of an internal standard to the sorbent helps to keep the overall analytical procedure under control and improves the reliability of needle trap micro-extraction for the analysis of volatile organic compounds at ultra-trace levels.

International audience; Biomarkers of oxidative stress are generally measured in blood and its derivatives. However, the invasiveness of blood collection makes the monitoring of such chemicals during exercise not feasible. Saliva analysis is an interesting approach in sport medicine because the collection procedure is easy-to-use and does not require specially-trained personnel. These features guarantee the collection of multiple samples from the same subject in a short span of time, thus allowing the monitoring of the subject before, during and after physical tests, training or competitions. The aim of this work was to evaluate the possibility of following the changes in the concentration of some oxidative stress markers in saliva samples taken over time by athletes under exercise. To this purpose, ketones (i.e. acetone, 2-butanone and 2-pentanone), aldehydes (i.e. propanal, butanal, and hexanal), α,β-unsaturated aldehydes (i.e. acrolein and methacrolein) and di-carbonyls (i.e. glyoxal and methylglyoxal) were derivatized with 2,4-dinitrophenylhydrazine, and determined by ultra-high performance liquid chromatography coupled to diode array detector. Prostaglandin E2, F2/E2-isoprostanes, F2-dihomo-isoprostanes, F4-neuroprostanes, and F2-dihomo-isofuranes were also determined by a reliable analytical procedure that combines micro-extraction by packed sorbent and ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry. Overall the validation process showed that the methods have limits of detection in the range of units of ppb for carbonyls and tens to hundreds of ppt for isoprostanes and prostanoids, very good quantitative recoveries (90–110%) and intra- and inter-day precision lower than 15%. The proof of applicability of the proposed analytical approach was investigated by monitoring the selected markers of oxidative stress in ten swimmers performing a VO2max cycle ergo meter test. The results highlighted a clear increase of salivary by-products of oxidative stress during exercise, whereas a sharp decrease, approaching baseline values, of these compounds was observed in the recovery phase. This study opens up a new approach in the evaluation of oxidative stress and its relation to aerobic activity.

Environmental pollution associated to plastic debris is gaining increasing relevance not only as a threat to ecosystems but also for its possible harmful effects on biota and human health. The release of toxic volatile organic compounds (VOCs) is a potential hazard associated with the environmental weathering of plastic debris. Artificial aging of reference polymers (polystyrene, polypropylene, polyethylene terephthalate, high and low density polyethylene) was performed in a Solar Box at 40 °C and 750 W/m2. The volatile degradation products were determined before and after 1, 2, 3 and 4 weeks of aging using a validated analytical procedure combining headspace (HS) with needle trap microextraction (NTME) and gas chromatography/mass spectrometry (GC–MS). A progressive increase in VOCs was observed during artificial photo-degradation, whose chemical profile resulted polymer-dependent and included carbonyls, lactones, esters, acids, alcohols, ethers, aromatics. The amount of extractable fraction in polar solvents generally showed a similar trend. The same analytical procedure was used to determine VOCs released from plastic debris collected at a marine beach. All samples released harmful compounds (e.g. acrolein, benzene, propanal, methyl vinyl ketone, and methyl propenyl ketone), supporting the initial hypothesis that microplastics represent an unrecognized source of environmental pollution.

This work presents a reliable analytical procedure combining micro-extraction by packed sorbent (MEPS) and ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry to determine 8-iso prostaglandin F2α, 8-iso prostaglandin E2 and prostaglandin E2 in dried blood spots (DBSs). To reach this goal, we optimized a fast semi-automated MEPS procedure for the clean-up and pre-concentration of the analytes extracted from a single DBS (50 μL) by a 70:30 v/v methanol:water mixture. Limits of detection of about 20 pg mL−1, satisfactory recoveries (90–110%) and very good intra- and inter-day precisions (RSD ≤10%) were obtained for all the analytes. The innovative addition of internal standards on the filter paper before DBS sampling allowed to compensate changes in the amount of analyte during storage. Since prostanoids and isoprostanoids are biomarkers involved in the pathogenesis and progression of many diseases (e.g. ductal patency, diabetic nephropathy, and acute lung injury), our analytical method offers interesting diagnostic and prognostic opportunities in the medical field. The present method is currently used for the analysis of such biomarkers in DBSs from preterm newborns collected in the clinical setting.