Microextraction-gas Chromatography-mass Spectrometry Method Research Articles

Strategies of Practical Implementation of Chemical Pre-Lithiation Using Lithium Arene Complex Solutions: A Systematic Study on Silicon-Based Anodes

Currently, Lithium ion batteries (LIBs) are state-of-the-art (SOTA) energy storage systems. There is an urgent need for further improvements in terms of gravimetric and volumetric energy of LIBs, for a successful market penetration of electric vehicles. Therefore, development of advanced negative electrode materials is of high interest. Here, silicon (Si) is a promising active material to replace SOTA graphite due to its ~10-fold higher specific capacity and being also high abundant.However, Si undergoes severe volume changes up to 280% during (de-)lithiation, resulting in fast capacity fading and short cycle life due to the continuous re-formation of the solid electrolyte interphase (SEI), leading to active lithium losses (ALL). In order to counteract ALL, research is focusing on suitable pre-lithiation processes. Among different pre-lithiation methods, chemical pre-lithiation by application of lithium arene complex (LAC) solutions is promising as it is a fast, easy and cost-effective method.In this work, the stability of three different solvents to produce a 4,4’-dimethylbiphenyl (4,4’-DMBP) LAC is investigated via solid phase microextraction gas chromatography-mass spectrometry method (SPME-GC-MS). The optimized LAC solution is used to evaluate the stability of different binder systems with respect to electrode manufacturing. Based on these fundamental insights, different parameters such as the reaction temperature (T) and pre-lithiation time (PL-t) are systematically investigated regarding suitable degrees of pre-lithiation (DOPL) of the negative electrode. DOPLs up to a plateau of 55% can be obtained by using 0.5 M 4,4’-DMBP in tetrahydrofuran (THF) as LAC solution. Higher temperature during the reaction reduces the PL-t until achieving a pre-lithiation plateau. The impact of the parameters T and PL-t towards the electrochemical performance of Si-based LIB full cells is thoroughly investigated. It is shown that this approach improves the cycle life of a silicon nanowire graphite composite negative electrode up to 600% compared to the pristine electrodes

An Efficient Solid-Phase Microextraction–Gas Chromatography–Mass Spectrometry Method for the Analysis of Methyl Farnesoate Released in Growth Medium by Daphnia pulex

Methyl farnesoate (MF), a juvenile hormone, can influence phenotypic traits and stimulates male production in daphnids. MF is produced endogenously in response to stressful conditions, but it is not known whether this hormone can also be released into the environment to mediate stress signaling. In the present study, for the first time, a reliable solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method was developed and validated for the ultra-trace analysis of MF released in growth medium by Daphnia pulex maintained in presence of crowding w/o MK801, a putative upstream inhibitor of MF endogenous production. Two different clonal lineages, I and S clones, which differ in the sensitivity to the stimuli leading to male production, were also compared. A detection limit of 1.3 ng/L was achieved, along with good precision and trueness, thus enabling the quantitation of MF at ultra-trace level. The achieved results demonstrated the release of MF by both clones at the 20 ng/L level in control conditions, whereas a significant decrease in the presence of crowding was assessed. As expected, a further reduction was obtained in the presence of MK801. These findings strengthen the link between environmental stimuli and the MF signaling pathway. Daphnia pulex, by releasing the juvenile hormone MF in the medium, could regulate population dynamics by means of an autoregulatory feedback loop that controls the intra- and extra-individual-level release of MF produced by endogenous biosynthesis.

Ultra-sensitive solid-phase Microextraction-Gas Chromatography-Mass spectrometry determination of polycyclic aromatic hydrocarbons in snow samples using a deep cavity BenzoQxCavitand.

A very sensitive and selective solid-phase microextraction-gas chromatography-mass spectrometry method based on the use of a deep cavity BenzoQxCavitand as innovative coating was developed and validated for the simultaneous determination of the 16 US-EPA priority pollutants polycyclic aromatic hydrocarbons (PAHs) in snow samples at ultra-trace levels. The presence of a 8.3Å deep hydrophobic cavity allowed the engulfment of all the 16 PAHs, providing enhanced selectivity also in presence of interfering aromatic pollutants at high concentration levels. Validation proved the reliability of the method for the determination of the investigated compounds achieving detection limits in the 0.03-0.30ng/L range, good precision, with relative standard deviations <18% and recovery rates in the 90.8(±2.1)%-109.6(±1.0)%. The detection of low-molecular weight PAHs in snow samples from Antarctica and Alps confirms the widespread occurrence of these compounds, thus assessing the impact of anthropogenic activities onto the environment.

Tracking the environmental fate of fipronil and three of its metabolites in garlic based on sampling rate-corrected in vivo solid phase microextraction combined with gas chromatography-mass spectrometry

In this study, a sampling rate-corrected in vivo solid-phase microextraction-gas chromatography-mass spectrometry method (SR-in vivo SPME-GC-MS) was constructed to simultaneously detect fipronil and three of its metabolites in garlic, and their environmental behavior was long-term monitored in in vivo mode. All of three fipronil metabolites were more difficult to degrade than the parent pesticide. The final degradation rates of the metabolites in garlic were in the range of 4.4%-25.1%, much lower than that of the parent (78.6%-85.8%). While their total residues amount was about 3 times as high as fipronil, exceeding the maximum residue limits regulated by China and the European Union. The steady-state concentrations of fipronil and its metabolites in garlic were positively correlated with the pesticide stress dose. In short, the established in vivo tracking method is efficient and convenient. The features of simple operation, fast analysis, acceptable sensitivity, non-harmful or non-lethal to plants, available repeated and long-term monitoring of the same organism make it attractive for in vivo tracking assay, it is of great significance for the guidance of rational use of fipronil and protection of food safety.

Comparison of microbiota and volatile organic compounds in milk from different sheep breeds

In this study, we compared the microbiota and volatile organic compounds (VOC) present in the milk obtained from 3 different sheep breeds, namely Merino, Lacaune, and Assaf. Udder milk was collected from 21 animals, 7 from each breed. Bacterial microflora was determined metagenomically by extracting the DNA from the milk and analyzing the V3-V4 region of the 16S rRNA gene. Headspace solid-phase microextraction gas chromatography-mass spectrometry method was used to analyze VOC. The metagenomic analysis revealed (for Merino, Lacaune, and Assaf milk, respectively) Firmicutes (66.32, 69.36, and 57.08%), Actinobacteria (19.09, 7.67, and 19.40%), Proteobacteria (13.76, 21.06, and 22.19%), and Bacteroidetes (0.84, 1.91, and 1.33%) phyla in the milk samples. Lactobacillus was highly abundant in the milk of 3 breeds (29.64, 43.50, and 18.70%). The genera constituting more than 2% of all bacteria in all groups were Jeotgalicoccus (7.19, 5.34, and 10.77%), Enterococcus (5.18, 9.78, and 3.64%), and Corynebacterium (4.08, 3.00, and 13.44%). A total of 32 different VOC were identified by headspace solid-phase microextration analysis with 9, 30, and 24 different compounds from Merino, Lacaune, and Assaf breeds, respectively. Although ketone was the most abundant compound in Merino milk (71.84%), hydrocarbons were the most detected in Lacaune and Assaf milk (37.18% and 55.42%, respectively). A positive correlation was found between acetone, which was detected at the highest level in all groups, with Salinicoccus, Alloiococcus, Psychrobacter, and Dietzia. In addition, a negative correlation was found between the Lactobacillus genus, detected at the highest level in all groups, with methyl cyclopentane, 3-methylheptane, octane, decane, 3,3-dimethyloctane, and dodecane. Thus, differences were observed in the bacterial microflora and VOC in the sheep milk from different breeds under different feeding and breeding conditions.

A fast-screening dispersive liquid-liquid microextraction-gas chromatography-mass spectrometry method applied to the determination of efavirenz in human plasma samples.

We demonstrate the suitability of a fast, green, easy-to-perform, and modified sample extraction procedure, i.e., dispersive liquid-liquid microextraction (DLLME) for the determination of efavirenz (EFV) in human plasma. Data acquisition was done by gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring (SIM) mode. The simplicity of the method lies in, among others, the avoidance of the use of large organic solvent volumes as mobile phases and non-volatile buffers that tend to block the plumbing in high-performance liquid chromatography (HPLC). Chromatographic and mass spectral parameters were optimized using bovine whole blood for matrix matching due to insufficient human plasma. Method validation was accomplished using the United States Food and Drug Administration (USFDA) 2018 guidelines. The calibration curve was linear with a dynamic range of 0.10-2.0μg/mL and an R2 value of 0.9998. The within-run accuracy and precision were both less than 20% at the lower limit of quantification (LLOQ) spike level. The LLOQ was 0.027μg/mL which compared well with some values but was also orders of magnitude better than others reported in the literature. The percent recovery was 91.5% at the LLOQ spike level. The DLLME technique was applied in human plasma samples from patients who were on treatment with EFV. The human plasma samples gave concentrations of EFV ranging between 0.14-1.00μg/mL with three samples out of seven showing concentrations that fell within or close to the recommended therapeutic range.

Study on the environmental fate of three insecticides in garlic by in vivo sampling rate calibrated-solid phase microextraction-gas chromatography-mass spectrometry

Traditional sample preparation methods for insecticide analysis are laborious and fatal to living organisms. In the work, an in vivo sampling rate calibrated-solid phase microextraction-gas chromatography-mass spectrometry method was established and successfully used for in vivo sampling and quantitative determination of three insecticides (hexachlorobenzene, fipronil and chlorfenapyr) by direct exposing micron-sized fiber in living garlic. Absorption, enrichment, migration and elimination behavior of insecticides in garlic were investigated. Bioaccumulative effects with obvious tissue differences were observed to all three insecticides, especially for chlorfenapyr. Bioconcentration factors (BCFs) ranging from 0.0342 to 1.0887 were obtained, and the closer to roots, the higher BCFs. The half-life of insecticides in garlic ranged from 0.43 to 0.96 d. In the first 24 h, 55.0% − 80.3% insecticides residues in garlic were eliminated with first-order elimination kinetics. The research provides in vivo insights into the environmental fates of insecticides in complex living system with minimized organism damage.

Polymeric metal-containing ionic liquid sorbent coating for the determination of amines using headspace solid-phase microextraction.

This study describes the design, synthesis, and application of polymeric ionic liquid sorbent coatings featuring nickel metal centers for the determination of volatile and semivolatile amines from water samples using headspace solid-phase microextraction. The examined polymeric ionic liquid (PIL) sorbent coatings were composed of two ionic liquid monomers (tetra(3-vinylimidazolium)nickel bis[(trifluoromethyl)sulfonyl]imide [Ni2+ (VIM)4 ]2[NTf2 - ] and 1-vinyl-3-hexylimidazolium [HVIM+ ][NTf2 - ]), and an ionic liquid cross-linker (1,12-di(3-vinylimidazolium)dodecane [(VIM)2 C12 2+ ]2[NTf2 - ]). With these ionic liquid monomers and cross-linkers, three different types of coatings were prepared: PIL1 based on the neat [Ni2+ (VIM)4 ]2[NTf2 - ] monomer, PIL2 consisting of the [Ni2+ (VIM)4 ]2[NTf2 - ] monomer with addition of cross-linker, and PIL3 composed of the [HVIM+ ][NTf2 - ] monomer and cross-linker. Analytical performance of the prepared sorbent coatings using headspace solid-phase microextraction gas chromatography-mass spectrometry was compared with the polydimethylsiloxane and polyacrylate commercial coatings. The PIL2 sorbent coating yielded the highest enrichment factors ranging from 5500 to over 160000 for the target analytes. The developed headspace solid-phase microextraction gas chromatography-mass spectrometry method was applied for the analysis of real samples (the concentration of amines was 200μg/L), producing relative recovery values in the range of 90.9-120.0% (PIL1) and 83.0-122.7% (PIL2) from tap water, and 84.8-112.4% (PIL1) and 79.2-119.3% (PIL2) from lake water.

Preliminary Study of Australian Pinot Noir Wines by Colour and Volatile Analyses, and the Pivot© Profile Method Using Wine Professionals.

The aim of this preliminary study was to identify potential colour components, volatile and sensory attributes that could discriminate Pinot noir wines from five Australian winegrowing regions (Adelaide Hills, Yarra Valley, Mornington Peninsula, Northern and Southern Tasmania). The sensory analysis consisted of the Pivot© Profile method that was performed by wine professionals. A headspace solid-phase microextraction-gas chromatography-mass spectrometry method was used to quantify multiple volatile compounds, while the Modified Somers method was used for colour characterisation. Analysis of data suggested ethyl decanoate, ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, in addition to decanoic acid as important contributors to the discrimination between regions. Similarly, wine hue, chemical age indices, total anthocyanin, and (%) non-bleachable pigment also discriminated wines between regions. The sensory analysis showed that wines from Mornington Peninsula were associated with the ‘red fruits’ aroma, ‘acidic’, and ‘astringency’ palate descriptors, while those from Adelaide Hills were associated with the ‘brown’ colour attribute. This study indicates regionality is a strong driver of aroma typicity of wine.

Combination of ultrasound-assisted ethyl chloroformate derivatization and switchable solvent liquid-phase microextraction for the sensitive determination of l-methionine in human plasma by GC-MS.

A green and fast analytical method for the determination of l-methionine in human plasma is presented in this study. Preconcentration of the analyte was carried out by switchable solvent liquid phase microextraction after ethyl chloroformate derivatization reaction. Instrumental detection of the analyte was performed by means of gas chromatography-mass spectrometry. N,N-Dimethyl benzylamine was used in the synthesis of switchable solvent. Protonated N,N-dimethyl benzylamine volume, volume/concentration of sodium hydroxide, and vortex period were meticulously fixed to their optimum values. Besides, ethyl chloroformate, pyridine, and ethanol volumes were optimized in order to get high derivatization yield. After the optimization studies, limit of detection and quantitation values were attained as 3.30 and 11.0ng/g, respectively, by the developed switchable solvent liquid phase microextraction gas chromatography-mass spectrometry method that corresponding to 76.7-folds enhancement in detection power of the gas chromatography-mass spectrometry system. Applicability and accuracy of the switchable solvent liquid phase microextraction-gas chromatography-mass spectrometry method were also checked by spiking experiments. Percent recovery results were ranged from 97.8 to 100.5% showing that human plasma samples could be analyzed for its l-methionine level by the proposed method.

A sensitive and accurate vortex-assisted liquid-liquid microextraction-gas chromatography-mass spectrometry method for urinary triazoles

The development and validation of an innovative, simple, rapid, selective and sensitive vortex-assisted liquid-liquid microextraction-gas chromatography- mass spectrometry (VALLME-GC/MS) method to seven triazole fungicides in urine is reported. The confidence parameters were exhaustive evaluated and linearity (r > 0.99), precision (below 15%, to quality controls, and 20%, to lower limit of quantification), accuracy and robustness were adequate for the analysis of cyproconazole, epoxiconazole, metconazole, tebuconazole, triadimenol, propiconazole and triadimefon. To assess the applicability of the method, analyses were performed in volunteers exposed to triazoles in the last 30 days. The method demonstrated satisfactory analytical performance, with sufficient detectability to be applied as a potential tool to biomonitoring individuals exposed to the seven evaluated fungicides.

Solid-phase microextraction of volatile organic compounds in headspace of PM-induced MRC-5 cell lines

The exploration of volatile organic compounds (VOCs) produced by cell lines may be a powerful and non-invasive tool for the study of the health risk of human exposure to atmospheric particulate matter (PM). In this work, we developed a sensitive solid phase microextraction-gas chromatography-mass spectrometry method (SPME-GC-MS) to analyze VOCs in breathed gas of PM2.5-induced human embryonic fibroblast cell line (MRC-5). A novel graphene oxide/polyaniline/polydopamine (GO/PANI/PDA) coating was prepared on a stainless steel wire via electrochemical deposition and self-polymerization for the first time. The GO/PANI/PDA coating exhibited high extraction efficiency, good thermal stability (> 380 ℃), excellent mechanical stability as well as long service time (> 150 times). Parameters that may affect the results were optimized systematically. Under the optimal conditions, VOCs including benzene series, aldehydes and alkane were detected with low limit of detection (0.2–2.0 μg L−1) and good correlation (correlation coefficients above 0.9922). The relative standard deviations of within-day and between-day were 1.1–8.4% and 0.2–11.2%, respectively. Satisfactory recoveries of 82–117% indicated good repeatability of the method. The method has been successfully applied for the determination of target VOCs in the headspace gas of PM2.5-induced MRC-5 cell. And it is expected to provide an alternative tool for the study of cytotoxicology of atmospheric particulates.

Evaluation of thirteen haloacetic acids and ten trihalomethanes formation by peracetic acid and chlorine drinking water disinfection

Free chlorine is a commonly used disinfectant in drinking water treatment. However, disinfection by-products (DBPs) are formed during water disinfection. Haloacetic acids (HAAs) and trihalomethanes (THMs) are two major groups of DBPs. Iodo-HAAs and iodo-THMs (I-HAAs and I-THMs) are formed during the disinfection of the water containing high levels of iodide and are much more toxic than their chlorinated and brominated analogs. Peracetic acid (PAA) is a strong antimicrobial disinfectant that is expected to reduce the formation of HAAs and THMs during disinfection. In this study, the formations of thirteen HAAs and ten THMs, including the iodinated forms, have been investigated during PAA disinfection and chlorination as the comparison. The DBP formations under different iodide concentrations, pHs, and contact times were systematically investigated. Two types of commercial PAAs containing different concentrations of PAA and hydrogen peroxide (H2O2) were studied. A solid-phase microextraction gas chromatography-mass spectrometry method was upgraded for THM analysis including I-THMs. HAAs were analyzed by following a recently developed high performance ion chromatography-tandem mass spectrometry method. Results show that the ratio of PAA and H2O2 concentration significantly affect the formation of I-THMs and I-HAAs. During PAA disinfection with lower PAA than H2O2, no detectable levels of THMs and HAAs were observed. During PAA disinfection with higher PAA than H2O2, low levels of monoiodoacetic acid, diiodoacetic acid, and iodoform were formed, and these levels were enhanced with the increase of iodide concentration. No significant quantities of chloro- or bromo-THMs and HAAs were formed during PAA disinfection treatment.

The detection of active moulds on historical silk by the means of the headspace–solid phase micro-extraction–gas chromatography–mass spectrometry method

The goal of this work was to analyze the profile of microbial volatile organic compounds (MVOCs) emitted by moulds growing on silk samples in search of particular volatiles mentioned in the literature as indicators of active mould growth. The selected moulds were inoculated on three types of media: (1) samples of pure silk placed on microbial media, (2) samples of historical silk placed on microbial media, and (3) agar containing amino acids that are elements of the structure of fibroin. All samples were prepared inside vials (closed system). In the first and second cases the media did not contain any sources of organic carbon, nitrogen, or sulfur—the silk was the only nutrient for the moulds. A fourth type of sample was historical silk prepared in a Petri dish without a microbial medium and inoculated with a fibroinolytically active mould (open system). The MVOCs emitted by moulds were sampled with the headspace–solid phase micro-extraction method. Volatiles extracted on Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) fibers were analyzed in a gas chromatography–mass spectrometry system. Qualitative and quantitative analyses of chromatograms were carried out in search of indicators of metabolic activity. The results showed that there are three groups of volatiles that can be used for the detection of active forms of moulds on silk. Thus, this can be a valuable tool for the fast detection of mould activity on historical silk objects. To the best of our knowledge, this is the first work to measure MVOCs emitted by moulds growing on silk.

Hollow fiber liquid-phase microextraction-gas chromatography-mass spectrometry method to analyze bisphenol A and other plasticizer metabolites

Phthalates and bisphenol A are important environmental pollutants due to their toxicity for humans and animals, including actions in the endocrine system. Their metabolites in urine can be used as biomarkers to assess human exposure. This paper describes the development of a new method to determine bisphenol A and eight phthalate metabolites in urine samples using hollow fiber liquid phase microextraction (HF-LPME) and gas chromatography-mass spectrometry (GC–MS). This method showed linearity, precision, limits of detection, and quantification suitable to analyze these compounds at low concentration levels in urine. Limits of detection ranged from 0.777 to 23.3μgL−1, showing sensitivity for evaluating environmental exposure. Relative standard deviation (RSD) ranged from 11.7 to 19.7%. The developed method presented a good biomarker alternative for evaluating environmental exposure to bisphenol A and phthalates.

Applicability of emanating volatile organic compounds from various forensic specimens for individual differentiation

Trace biological materials contain volatile profiles that have yet to be evaluated to determine their value in forensic investigations. The volatiles released by different biological specimens (hand odor, hair, fingernails and saliva) collected from twenty individuals were identified using a solid phase microextraction–gas chromatography–mass spectrometry method. The human scent compounds from each specimen, per subject, were evaluated using Spearman rank correlation to assess the applicability of these compounds for the differentiation of individuals. The volatile organic compounds from each specimen type were readily identified and discriminated. When conducting inter-subject discrimination within a single specimen type, greater than 98.9% of the samples, or individuals, were differentiated for all specimen types. When conducting inter-subject discrimination among the four specimen types 99.6% of the samples were differentiated, at the 0.9 correlation coefficient threshold. Additionally, the only occurrence of cross-correlation between specimen types was observed between hair and fingernails while there were no cross-correlations with hand odor or saliva thereby demonstrating the distinctiveness of these specimens.

Characterization of cocoa liquors by GC–MS and LC–MS/MS: focus on alkylpyrazines and flavanols

Flavor is one of the most important characteristics of chocolate products and is due to a complex volatile fraction, depending both on the cocoa bean genotype and the several processes occurring during chocolate production (fermentation, drying, roasting and conching). Alkylpyrazines are among the most studied volatiles, being one of the main classes of odorant compounds in cocoa products. In this work, a mass spectrometric approach was used for the comparison of cocoa liquors from different countries. A headspace solid-phase microextraction gas chromatography-mass spectrometry method was developed for the qualitative study of the volatile fraction; the standard addition method was then used for the quantitative determination of five pyrazines (2-methylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine and tetramethylpyrazine). Satisfactory figures of merit were obtained: Limits of quantitation were in the range 0.1-2.7 ng/g; repeatability and reproducibility varied between 3% and 7% and between 8% and 14%, respectively. The total content of the pyrazines was remarkably different in the considered samples, ranging from 99 to 708 ng/g. Tetramethylpyrazine showed the highest concentration in all samples, with a maximum value of 585 ng/g. A preliminary study was also performed on the nonvolatile fraction using LC-MS/MS, identifying some flavanols such as catechin, epicatechin and procyanidins.

Response surface optimisation applied to a headspace-solid phase microextraction-gas chromatography-mass spectrometry method for the analysis of volatile organic compounds in water matrices

A new method for the simultaneous determination of 12 volatile organic compounds (trans-1,2-dichloroethene, 1,1,1-trichloroethane, benzene, 1,2-dichloroethane, trichloroethene, toluene, 1,1,2-trichloroethane, tetrachloroethene, ethylbenzene, m-, p-, o-xylene) in water samples by headspace solid phase microextraction (HS–SPME)–gas chromatography mass spectrometry (GC–MS) was described, using a 100 µm PDMS (polydimethylsiloxane) coated fibre. The response surface methodology was used to optimise the effect of the extraction time and temperature, as well as the influence of the salt addition in the extraction process. Optimal conditions were extraction time and temperature of 30 min and −20°C, respectively, and NaCl concentration of 4 mol L−1. The detection limits were in the range of 1.1 × 10−3–2.3 µg L−1 for the 12 volatile organic compounds (VOCs). Global uncertainties were in the range of 4–68%, when concentrations decrease from 250 µg L−1 down to the limits of quantification. The method proved adequate to detect VOCs in six river samples.

Simultaneous Determination of Parathion, Malathion, Diazinon, and Pirimiphos Methyl in Dried Medicinal Plants Using Solid-Phase Microextraction Fibre Coated with Single-Walled Carbon Nanotubes

A reliable and sensitive headspace solid-phase microextraction gas chromatography-mass spectrometry method for simultaneous determination of different organophosphorus pesticides in dried medicinal plant samples is described. The analytes were extracted by single-walled carbon nanotubes as a new solid-phase microextraction adsorbent. The developed method showed good performance. For diazinon and pirimiphos methyl calibration, curves were linear (r 2 ≥ 0.993) over the concentration ranges from 1.5 to 300 ng g−1, and the limit of detection at signal-to-noise ratio of 3 was 0.3 ng g−1. For parathion and malathion, the linear range and limit of detection were 2.5–300 (r 2 ≥ 0.991) and 0.5 ng g−1, respectively. In addition, a comparative study between the single-walled carbon nanotubes and a commercial polydimethylsiloxane fibre for the determination of target analytes was carried out. Single-walled carbon nanotubes fibre showed higher extraction capacity, better thermal stability (over 350°C), and longer lifespan (over 250 times) than the commercial polydimethylsiloxane fibre. The developed method was successfully applied to determine target organophosphorus pesticides in real samples.

Solid-phase microextraction–gas chromatography–mass spectrometry method validation for the determination of endogenous substances: Urinary hexanal and heptanal as lung tumor biomarkers

Hexanal and heptanal are endogenous aldehydes coming from membrane lipid oxidation, found in lung cancer patients’ blood, and suggested as lung tumor biomarkers. Here the urinary matrix was investigated instead of blood and the difficulties related to the determination of endogenous substances in biological matrices were faced by developing an external calibration HS-SPME/GC/MS method. The methodology was validated according to international validation procedures and it was verified analyzing unknown biological samples from cancer patients and healthy subjects. Percentage accuracy and precision, ranging from −11.25 to 10.85% and from 0.45 to 4.46%, respectively, were obtained, together with limits of detection (LODs) and lower limits of quantification (LLOQs) of 0.11 and 0.23 pg μL −1 for hexanal and of 0.10 and 0.21 pg μL −1 for heptanal. Analytes percentage recoveries (66.3%, hexanal and 70.5%, heptanal) and stability were evaluated. No analytes degradation was found at room temperature, while the remarkable analytes loss found after 1 month storage suggests analyzing biological samples within a week from storage. Results coming from the analysis of unknown biological samples showed no evident differences of heptanal urinary excretion between lung cancer patients and healthy subjects (0.22–0.95 and 0.21–0.69 pg μL −1, respectively), while hexanal urinary concentrations in cancer patients (0.24–4.36 pg μL −1) were slightly higher than those found in control group ones (0.23–1.26 pg μL −1). The obtained results highly suggest to do further investigations in order to collect statistically significant biological data to discriminate between the pathological state of lung cancer patients and physiological conditions of healthy subjects, using the simple, rapid and cheap method here reported for the quantification of urinary aldehydes.