Exploring sorption of pesticides and PAHs in microplastics derived from plastic mulch films used in modern agriculture.

The sorption and vector effect of microplastics on the transfer of pesticides and polycyclic aromatic hydrocarbons (PAHs), as well as its impact on agriculture remain largely unexplored. This comparative study is first to investigate the sorption behavior of different pesticides and PAHs at environmentally realistic concentrations by model microplastics and microplastics derived from polyethylene mulch films. Sorption was found to be up to 90% higher in the case of microplastics derived from mulch films as opposed to pure polyethylene microspheres. For microplastics from mulch films, the sorption percentages for pesticides in media containing CaCl2 were reported to be: pyridate (75.68% and 52.44%), fenazaquin (48.54% and 32.02%), pyridaben (45.04% and 56.70%), bifenthrin (74.27% and 25.88%), etofenprox (82.16% and 54.16%) and pyridalyl (97.00% and 29.74%) at 5 µg/L and 200 µg/L pesticide concentration levels respectively. For PAHs, the sorption amounts were: naphthalene (22.03% and 48.00%), fluorene (38.99% and 39.00%), anthracene (64.62% and 68.02%) and pyrene (75.65% and 86.38%) at 5 µg/L and 200 µg/L PAH concentration levels respectively. Sorption was influenced by the octanol-water partition coefficient (log Kow) and ionic strength. Kinetics of the process in the case of sorption of pesticides were best explained by pseudo-first order kinetic model (R2 between 0.90 and 0.98) while the best fitting isotherm model was Dubinin-Radushkevich (R2 between 0.92 and 0.99). Results suggest the presence of surface level physi-sorption through a micropore volume filling mechanism and the role of hydrophobic and electrostatic forces. Pesticide desorption data in polyethylene mulch films indicate that pesticides with high log Kow were almost completely retained in mulch films, while those with lower log Kow were desorbed rapidly into the surrounding media. Our study highlights the role of microplastics from plastic mulch films as vectors for pesticide and PAH transport at environmentally realistic concentrations and the factors that influence it.

High-throughput gas chromatography-mass spectrometry analysis of pesticide residues in spices by using the enhanced matrix removal-lipid and the sample dilution approach.

Spices are known as difficult matrices that contain variable amounts of fats, piperine or many other matrix constituents. The increasing sensitivity of new GC-MS/MS platforms opens new approaches to analyze pesticide residue in complex matrices such as spices, by sample dilution. The aim of this work is to develop and validate an effective multiresidue method for the analysis of pesticide residues in spices by GC-MS/MS. In this paper, we highlight the importance of reducing matrix interferences generated from co-extractive components of spices. Moreover, we emphasize the concern of obtaining clean extracts requiring less instrument maintenance. By evaluating the total ion chromatograms (TIC) on GC-Orbitrap-MS of different extracts using various sorbents, QuEChERS citrate using EMR-Lipid sorbent resulted in the cleanest extract among Z-Sep, Primary secondary amine (PSA), Oasis® Prime HLB, and Supelclean™ Ultra cartridges that consist of a top bed of PSA, C18 and Grashsphere™ 2031 and a bottom bed of Z-Sep. Later, the analyses were performed on a GC-QQQ-MS/MS, applying a 15 min runtime method covering 205 compounds. The samples were diluted 25 times before the injection bearing in mind that the instrumental LOQs reached (iLOQ) were 2 ng g-1 and the method LOQs (mLOQ) were 50 ng g-1. Good recoveries between 70 and 120% with RSDs lower than 20% were observed for 90% of the compounds in black pepper and for 83% of the compounds in cayenne pepper. To demonstrate the applicability of the proposed method, 50 real dried and non-dried spice samples were analyzed. The most detected pesticides were metalaxyl, chlorpyrifos, tebuconazole, ethion, and chinomethionate.

Matrix interference evaluation employing GC and LC coupled to triple quadrupole tandem mass spectrometry.

Gas and liquid chromatography coupled to triple quadrupole tandem mass spectrometry are currently the most powerful tools employed for the routine analysis of pesticide residues in food control laboratories. However, whatever the multiresidue extraction method, there will be a residual matrix effect making it difficult to identify/quantify some specific compounds in certain cases. Two main effects stand out: (i) co-elution with isobaric matrix interferents, which can be a major drawback for unequivocal identification, and therefore false negative detections, and (ii) signal suppression/enhancement, commonly called the "matrix effect", which may cause serious problems including inaccurate quantitation, low analyte detectability and increased method uncertainty. The aim of this analytical study is to provide a framework for evaluating the maximum expected errors associated with the matrix effects. The worst-case study contrived to give an estimation of the extreme errors caused by matrix effects when extraction/determination protocols are applied in routine multiresidue analysis. Twenty-five different blank matrices extracted with the four most common extraction methods used in routine analysis (citrate QuEChERS with/without PSA clean-up, ethyl acetate and the Dutch mini-Luke "NL" methods) were evaluated by both GC-QqQ-MS/MS and LC-QqQ-MS/MS. The results showed that the presence of matrix compounds with isobaric transitions to target pesticides was higher in GC than under LC in the experimental conditions tested. In a second study, the number of "potential" false negatives was evaluated. For that, ten matrices with higher percentages of natural interfering components were checked. Additionally, the results showed that for more than 90% of the cases, pesticide quantification was not affected by matrix-matched standard calibration when an interferent was kept constant along the calibration curve. The error in quantification depended on the concentration level. In a third study, the "matrix effect" was evaluated for each commodity/extraction method. Results showed 44% of cases with suppression/enhancement for LC and 93% of cases with enhancement for GC.

Non-target evaluation of contaminants in honey bees and pollen samples by gas chromatography time-of-flight mass spectrometry.

This work presents a non-targeted screening approach for the detection and quantitation of contaminants in bees and pollen, collected from the same hive, by GC-EI-ToF-MS. It consists of a spectral library datasets search using a compound database followed by a manual investigation and analytical standard confirmation together with semi-quantitation purposes. Over 20% of the compounds found automatically by the library search could not be confirmed manually. This number of false positive detections was mainly a consequence of an inadequate ion ratio criterion (±30%), not considered in the automatic searching procedure. Eight compounds were detected in bees and pollen. They include insecticides/acaricides (chlorpyrifos, coumaphos, fluvalinate-tau, chlorfenvinphos, pyridaben, and propyl cresol) at a concentration range of 1-1207 µg kg-1, herbicides (oxyfluorfen) at a concentration range of 212-1773 µg kg-1 and a growth regulator hormone (methoprene). Some compounds were detected only in pollen; such as herbicides (clomazone), insecticides/acaricides and fungicides used to control Varroa mites as benzylbenzoate, bufencarb, allethrin, permethrin, eugenol and cyprodinil. Additional compounds were detected only in bees: flamprop-methyl, 2-methylphenol (2-49 µg kg-1) and naphthalene (1-23 µg kg-1). The proposed method presents important advantages as it can avoid the use of an unachievable number of analytical standards considered target compounds "a priori" but not present in the analyzed samples.

Identification of non-intentionally added substances in food packaging nano films by gas and liquid chromatography coupled to orbitrap mass spectrometry.

The control of chemical migration from new functionalized food contact materials (FCMs) is a challenge for meeting food safety requirements. The non-intentionally added substances (NIAS) constitute a group of chemicals that are not applied, but may be introduced or formed during the production process of FCMs. This study describes a multi-analytical approach for the evaluation of unknown substances that migrate from FCMs. A case study is presented using a developed polymer consisting of a monolayer film with polylactic acid (PLA), polylimonene (PL) and zinc oxide nanoparticles (ZnO NPs). This approach incorporates the platforms of ICP-MS (inductively coupled plasma mass spectrometry), to determine whether there is transference of ZnO NPs used as antimicrobial agent and, the systems GC-MS and LC-MS (gas / liquid chromatography coupled to a quadrupole orbitrap mass spectrometer) for the characterization of the chemical structure of NIAS using the molecular mass and specific features of mass fragmentation. The screening of unknown compounds comprised retrospective analysis and data processing using both, a mass spectral library and databases, for GC and LC data, respectively. This approach has provided the tentative identification and quantification of seven NIAS, 3 by GC (Tripropylene glycol diacrylate, 10-Heneicosene and α-Tocopherol acetate) and 4 by LC (N,N-Diethyldodecanamide, N-[(9Z)-9-Octadecen-1-yl]acetamide, 1-Palmitoylglycerol and Glycerol stearate). This migration study was carried out according to the standard protocols established by EU regulation for FCMs.

Shifting the paradigm in gas chromatography mass spectrometry pesticide analysis using high resolution accurate mass spectrometry.

In the last 10 years, the majority of the pesticide food control laboratories moved from GC-MS to GC-MS/MS as the preferred analytical technique to address GC amenable compounds. The main reason for this change was the negative impact on the single stage GC-MS analysis caused by the interference from coeluting matrix compounds. The new development of gas chromatography coupled to high resolution accurate mass spectrometry (GC-HRAMS) provides opportunities to overcome such matrix interferences as a result of its much higher selectivity; allowing laboratories to carry out full-scan analysis covering the most exigent analytical performance criteria. The aim of this work is the evaluation of the main analytical performance parameters for the multiresidue screening of pesticide residues by a gas chromatography-Orbitrap™ mass spectrometer in fruits and vegetables. Electron ionization and full-scan high resolution mass spectrometry was selected for this evaluation. Mass resolving power, selectivity, sensitivity, analyte identification and database generation are discussed in light of the analysis of various commodities and a large scope of pesticides. The selected operational conditions provided optimal mass accuracy, within ±1mDa and achieved LOQs of 10µg/kg or lower for practically all the selected pesticides and commodities. Applicability for quantitative residue analysis was verified by the validation of the 210 pesticides in four matrices (tomato, apple, leek and orange). The performance of the GC-EI-full scan Orbitrap HRAMS developed method was confirmed with the analysis of 102 real samples providing good results.

Large multiresidue analysis of pesticides in edible vegetable oils by using efficient solid-phase extraction sorbents based on quick, easy, cheap, effective, rugged and safe methodology followed by gas chromatography-tandem mass spectrometry.

The aim of this research was to adapt the QuEChERS method for routine pesticide multiresidue analysis in edible vegetable oil samples using gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Several clean-up approaches were tested: (a) D-SPE with Enhanced Matrix Removal-Lipid (EMR-Lipid™); (b) D-SPE with PSA; (c) D-SPE with Z-Sep; (d) SPE with Z-Sep. Clean-up methods were evaluated in terms of fat removal from the extracts, recoveries and extraction precision for 213 pesticides in different matrices (soybean, sunflower and extra-virgin olive oil). The QuEChERS protocol with EMR-Lipid d-SPE provided the best reduction of co-extracted matrix compounds with the highest number of pesticides exhibiting mean recoveries in the 70-120% range, and the lowest relative standard deviations values (4% on average). A simple and rapid (only 5min) freeze-out step with dry ice (CO2 at -76°C) prior to d-SPE clean-up ensured much better removal of co-extracted matrix compounds in compliance of the necessity in routine analysis. Procedural Standard Calibration was established in order to compensate for recovery losses of certain pesticides and possible matrix effects. Limits of quantification were 10µgkg(-1) for the majority of the pesticides. The modified methodology was applied for the analysis of different 17 oil samples. Fourteen pesticides were detected with values lower than MRLs and their concentration ranged between 10.2 and 156.0µgkg(-1).

Screening of environmental contaminants in honey bee wax comb using gas chromatography-high-resolution time-of-flight mass spectrometry.

This study reports an analytical approach intended to be used for investigation of non-targeted environmental contaminants and to characterize the organic pollution pattern of bee wax comb samples. The method comprises a generic extraction followed by detection with gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC-TOF-MS), operated in electron impact ionization (EI) mode. The screening approach for the investigation of non-targeted contaminants consisted of initial peak detection by deconvolution and matching the first-stage mass spectra EI-MS(1) with a nominal mass spectral library. To gain further confidence in the structural characterization of the contaminants under investigation, the molecular formula of representative ions (molecular ion when present in the EI spectrum) and, for at least other two fragment ions, was provided for those with an accurate mass scoring (mass error < 5 ppm). This methodology was applied for screening environmental contaminants in 50 samples of bee wax comb. This approach has allowed the tentative identification of some GC-amenable contaminants belonging to different chemical groups, among them, phthalates and polycyclic aromatic hydrocarbons (PAHs), along with residues of veterinary treatments used in apiculture.

A sensitive and efficient method for routine pesticide multiresidue analysis in bee pollen samples using gas and liquid chromatography coupled to tandem mass spectrometry.

Several clean-up methods were evaluated for 253 pesticides in pollen samples concentrating on efficient clean-up and the highest number of pesticides satisfying the recovery and precision criteria. These were: (a) modified QuEChERS using dSPE with PSA+C18; (b) freeze-out prior to QuEChERS using dSPE with PSA+C18; (c) freeze-out prior to QuEChERS using dSPE with PSA+C18+Z-Sep; and (d) freeze-out followed by QuEChERS using dSPE with PSA+C18 and SPE with Z-Sep. Determinations were made using LC-MS/MS and GC-MS/MS. The modified QuEChERS protocol applying a freeze-out followed by dSPE with PSA+C18 and SPE clean-up with Z-Sep was selected because it provided the highest number of pesticides with mean recoveries in the 70-120% range, as well as relative standard deviations (RSDs) typically below 20% (12.2% on average) and ensured much better removal of co-extracted matrix compounds of paramount importance in routine analysis. Limits of quantification at levels as low as 5µgkg(-1) were obtained for the majority of the pesticides. The proposed methodology was applied to the analysis of 41 pollen bee samples from different areas in Spain. Pesticides considered potentially toxic to bees (DL50<2µg/bee) were detected in some samples with concentrations up to 72.7µgkg(-1), which could negatively affect honeybee health.

Accurate determination of selected pesticides in soya beans by liquid chromatography coupled to isotope dilution mass spectrometry.

A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18 column using gradient elution with water-methanol/2.5 mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-(13)C2(15)N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005 mg kg(-1) in the matrix, while LOQs established as the lowest spiking mass fractionation level were in the range 0.01-0.05 mg kg(-1). The method reliably identifies and quantifies the selected pesticides in soya beans at appropriate uncertainty levels, making it suitable for the characterization of candidate reference materials.

Processing factor for a selected group of pesticides in a wine-making process: distribution of pesticides during grape processing.

The processing factors (the pesticide concentration found in the wine/pesticide concentration found in grapes) of acetamiprid, azoxistrobin, carbaril, carbendazime, cyprodinil, dimethoate, dimethormorf, imazalil, imidacloprid, kresoxim methyl, penconazole, procymidone and thiabendazole were determined in a wine-making process. Pesticide analysis was performed using a multi-residue method for the determination of different pesticides both in wine and in grapes by extraction with acetonitrile followed by LC/MS. The pesticide distribution was studied for each step of the process, and the pesticide processing factors were calculated and found to vary among the different pesticides studied. pKow was found to affect a pesticide's processing factor; a linear correlation was obtained for all pesticide processing factors, except for dimethoate, which was the most water soluble. However, no correlation was found between the processing factor and the water solubility of pesticides.

Investigation of Galaxolide degradation products generated under oxidative and irradiation processes by liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry and comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry.

RATIONALE: Polycyclic musks have become a concern due to their bioaccumulation potential and ecotoxicological effects. The HHCB transformation product (TP) (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta[γ]-2-benzopyran; HHCB-lactone) is the most stable intermediate generated and it is frequently detected in river waters. The aim of this work was the identification of relevant TPs generated from UV irradiation and ozone treatments. METHODS: Identification of HHCB TPs was carried out by liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry (LC/ESI-QTOF-MS) and two-dimensional gas chromatography/electron impact time-of-flight mass spectrometry (GC×GC-EI-TOF-MS). With LC/ESI-QTOF-MS, TPs were characterized by means of mass accuracy in both full-scan and MS/MS modes through information-dependent acquisition (IDA) and direct injection on-column. With stir bar sorptive extraction (SBSE)-GC×GC-EI-TOF-MS, identification was based on the enhanced separation capacity and screening of unknowns through the acquisition of full-range mass spectra. RESULTS: The effectiveness of these complementary techniques allowed a detailed evaluation of the main TPs. Eighteen TPs were elucidated based on mass accuracy, in both full-scan and MS/MS modes using LC/ESI-QTOF-MS with mass errors below 5 ppm and 10 ppm (mostly), respectively. Most of the TPs had not been analytically identified in previous studies. Separation of the enantiomeric species (R) and (S) of HHCB-lactone, and the identification of other relevant TPs, was performed using SBSE-GC×GC-EI-TOF-MS. CONCLUSIONS: LC/ESI-QTOF-MS and GC×GC-EI-TOF-MS analysis provides the best alternative for TP identification of chemicals of concern, which have a wide range of polarities and isobaric compounds. A prediction of PBT (persistence, bioaccumulation and toxicity) using the PBT Profiler program suggested a classification of 'very persistent' and 'very toxic' for most of the TPs identified.

Prediction of the processing factor for pesticides in apple juice by principal component analysis and multiple linear regression.

The main objective of this work was to establish a mathematical function that correlates pesticide residue levels in apple juice with the levels of the pesticides applied on the raw fruit, taking into account some of their physicochemical properties such as water solubility, the octanol/water partition coefficient, the organic carbon partition coefficient, vapour pressure and density. A mixture of 12 pesticides was applied to an apple tree; apples were collected after 10 days of application. After harvest, apples were treated with a mixture of three post-harvest pesticides and the fruits were then processed in order to obtain apple juice following a routine industrial process. The pesticide residue levels in the apple samples were analysed using two multi-residue methods based on LC-MS/MS and GC-MS/MS. The concentration of pesticides was determined in samples derived from the different steps of processing. The processing factors (the coefficient between residue level in the processed commodity and the residue level in the commodity to be processed) obtained for the full juicing process were found to vary among the different pesticides studied. In order to investigate the relationships between the levels of pesticide residue found in apple juice samples and their physicochemical properties, principal component analysis (PCA) was performed using two sets of samples (one of them using experimental data obtained in this work and the other including the data taken from the literature). In both cases the correlation was found between processing factors of pesticides in the apple juice and the negative logarithms (base 10) of the water solubility, octanol/water partition coefficient and organic carbon partition coefficient. The linear correlation between these physicochemical properties and the processing factor were established using a multiple linear regression technique.

A sensitive and selective method for the determination of selected pesticides in fruit by gas chromatography/mass spectrometry with negative chemical ionization.

Multiresidue methods (MRMs) for pesticides residues determination in fruit and vegetables, based on GC-MS, are mainly performed in electron impact ionization mode. However an important group of them provide much better response working in negative chemical ionization mode due to the elimination of a high percentage of background signal. Considering that a selective and sensitive method has been developed for the determination of multiclass pesticide residues in different commodities by GC-MS with a triple stage quadrupole analyzer (GC-TSQ-MS); the pesticide signal has been optimized in MS-MS whilst working in negative chemical ionization mode using methane as the reagent gas. The proposed method was fully validated for 53 compounds in tomato, apple and orange matrices. The obtained limits of determination were lower than 0.1 µg/kg for more than 50% of the pesticides studied, and lower than 1 µg/kg for all pesticides studied, except for cypermethrin, boscalid, bifenthrin and deltamethrin. Linearity was studied in the 0.5-50 µg/kg range and a linear response was obtained for all pesticides in all matrices. Recoveries were evaluated at two different levels (1 and 50 µg/kg) and recoveries were ranged between 70 and 120% in tomato, apple and orange, except in the cases of chlorfenapyr, ofurace, chlozolinate, chlorothalonil, tolylfluanid and dichlofluanid with recovery values close to 60% at 1 µg/kg fortification levels. Repetitivity was evaluated and the relative standard deviation (RSD%) was lower than 10% in all cases. The developed method was employed in the analysis of real samples intended for baby food and the obtained results showed that 50% of the samples were positive for different pesticide residues. The concentration range detected was between 5 and 100 µg/kg. The positive detection of OCs was particularly noticeable; these included chlorothalonil, fenhexamide, clorpyrifos and lambda cyhalothrin, which are very persistent and toxic with low acute reference dose. Endosulfan sulfate, which is not approved, was detected at a low concentration.

Determination of chlorothalonil in difficult-to-analyse vegetable matrices using various multiresidue methods.

The molecular characteristics of chlorothalonil can cause particular determination difficulties in some vegetable commodities such as leek or garlic. These difficulties are mainly related to the low recoveries obtained using common multi-residue methods (MRMs)--a consequence of the very high interaction level with natural components in the matrix. These shortcomings were pointed out in the last European Proficiency Test for Pesticide Residues on Fruits and Vegetables, where false negatives for chlorothalonil in leek were observed at around 50%. In this study we have evaluated the ethyl acetate, the Dutch mini-Luke and the QuEChERS MRMs to compare their capabilities for chlorothalonil determination using GC-MS/MS in both the electron impact ionization (EI) and negative chemical ionization (NCI) modes. Best recoveries (in the range of 100-120%, with an RSD below 20%) were obtained using the Dutch mini-Luke method. Lower values (52-70%) were obtained for ethyl acetate whereas no recovery was obtained when the QuEChERS method was applied. Furthermore, tomato matrix was also included in the experiments in order to facilitate the comparability of results. Two ionization modes, electron impact ionization (EI) and negative chemical ionization (NCI) in GC-MS/MS, were applied to evaluate their respective advantages and disadvantages for quantification and identification. As expected, NCI showed limits of detection (LODs) 5 to 10 times lower than EI. However, in both cases, the LODs were still below 10 µg kg(-1). The proposed optimal method was applied for chlorothalonil determination in leek and garlic with good results--in accordance with the European Union (EU) Analytical Quality Control (AQC) Guidelines for pesticides analysis.

Determination of selected pesticides by GC with simultaneous detection by MS (NCI) and µ-ECD in fruit and vegetable matrices.

A gas chromatography-mass spectrometry method in negative chemical ionization mode has been developed incorporating simultaneous detection using a micro-electron capture detector (µ-ECD) for the determination of pesticides in fruits and vegetables. This instrument configuration uses a three-way splitter device which divides the effluent from the analytical column between the two detectors with the split ratio 1:0.1 (MSD/µ-ECD) in each run. The µ-ECD was used for confirmation purposes. Validation of the method was performed on three matrices: tomato, apple, and orange. The ethyl acetate method was assayed; recovery studies were performed at 10 and 100 µg/kg. Recoveries between 70% and 120% were achieved and relative standard deviations lower than 20% (n = 5) were obtained for all pesticides and matrices studied. Limits of quantification lower than 10 µg/kg were obtained for 100% of pesticides in all of the matrices. Limits of quantification lower than 2.5 µg/kg were achieved for 77.8% of pesticides in the tomato and apple matrices, and for 72.2% of pesticides in the orange matrix. The method showed linear response in the concentration range tested (2.5-500 µg/kg) with correlation coefficients >0.99. Good repeatability and reproducibility results were obtained in all cases, with relative standard deviations lower than 16.7% and 20%, respectively. Finally, 20 incurred samples were analyzed using the proposed method. The simultaneous use of the two detectors was satisfactory for the analysis of these real samples. The total number of pesticides identified was 25. The number of samples which contained at least one pesticide was 15-this represented 75% of the total number of samples studied.

Determination of nicotine in mushrooms by various GC/MS- and LC/MS-based methods.

Due to the basic properties of nicotine, it is not easily integrated into commonly used multiresidue methods. The present work investigates the application of two commonly employed multiresidue methods-the QuEChERS method and the ethyl acetate method-for determining nicotine in mushrooms. Both methods are employed in a modified form and an unmodified form: the former to address the special properties of nicotine and the latter, combined with the use of isotopically labelled nicotine, to compensate for poor recoveries. The QuEChERS-based methods were followed by liquid chromatography-time-of-flight mass spectrometry and those based on ethyl acetate extraction were followed by gas chromatography-triple quadrupole-mass spectrometry. All methods were validated according to European guidelines (document no. SANCO/10684/2009). Recovery studies performed on mushroom spiked at 10 and 100 µg kg(-1) yielded average recoveries in the range 80-110% with relative standard deviation (RSD) values below 9%. The linearity of the response over two orders of magnitude was demonstrated (r(2) > 0.995) for all of the determination techniques employed. The limits of detection and quantification obtained were in the 0.7 and 10 µg kg(-1) range, depending on the technique, and thus below the maximum residue level established for this toxic alkaloid by current EU legislation. Good repeatability and reproducibility were obtained in terms of the RSD of the analytical methods (0.4-13.2%). The modified QuEChERS method was tested in a proficiency test on nicotine in dried mushrooms obtaining good results. The methods were successfully applied to 20 real samples.

Trace analysis of pesticides in paddy field water by direct injection using liquid chromatography-quadrupole-linear ion trap-mass spectrometry.

A multiresidue method was developed for the quantification and confirmation of 70 pesticides in paddy field water. After its filtration, water was injected directly in a liquid chromatograph coupled to a hybrid triple quadrupole-linear ion trap-mass spectrometer (QqLIT). The list of target analytes included organophosphates, phenylureas, sulfonylureas, carbamates, conazoles, imidazolinones and others compounds widely used in different countries where rice is cropped. Detection and quantification limits achieved were in the range from 0.4 to 80 ng L(-1) and from 2 to 150 ng L(-1), respectively. Correlation coefficients for the calibration curves in the range 0.1-50 µg L(-1) were higher than 0.99 except for diazinon (0.1-25 µg L(-1)). Only 9 pesticides presented more than 20% of signal suppression/enhancement, no matrix effect was observed in the studied conditions for the rest of the target pesticides. The method developed was used to investigate the occurrence of pesticides in 59 water samples collected in paddy fields located in Spain and Uruguay. The study shows the presence of bensulfuron methyl, tricyclazole, carbendazim, imidacloprid, tebuconazole and quinclorac in a concentration range from 0.08 to 7.20 µg L(-1).

Development and validation of a LC-MS/MS method for the simultaneous determination of aflatoxins, dyes and pesticides in spices.

Based on several alerts from European countries over the last years concerning spices, we have been encouraged to establish an accurate method for the determination of dyes, aflatoxins and pesticides in various types of spices using reversed-phase (RP) liquid chromatography-tandem mass spectrometry interfaced with electrospray (LC-ESI-MS/MS). A simple sample treatment procedure entailing the use of an extraction step with acetonitrile without further cleanup has been developed. A C18 column with an aqueous ammonium formate/methanol mixture as the mobile phase was used, and gradient elution was performed. Mass spectral acquisition was done in positive ion mode by applying multiple reaction monitoring of at least two fragmentation transitions per compound to provide a high degree of selectivity. The method was in-house validated in terms of linearity, sensitivity, repeatability, recovery and selectivity on six kinds of spices. Satisfactory results in the majority of the cases were obtained for all analytes and matrices, with practical limits of quantitation acceptable for routine monitoring purposes. Extraction recoveries for most of the compounds ranged from 60% to 140% at spiking levels of 0.05 and 0.5 mg kg(-1). The applicability of the method for the simultaneous determination of dyes, aflatoxins and pesticides in several types of spices was demonstrated, and the method successfully applied to a limited number of products from the local market.

A new gas chromatography/mass spectrometry method for the simultaneous analysis of target and non-target organic contaminants in waters.

In this study we developed a GC-MS method for the analysis of priority pollutants, personal care products (PCPs) and other emerging contaminants in waters using large volume injection with backflushing. Analyses are performed in the SIM/scan mode, so that in addition to the targeted organic contaminants, this method allows the simultaneous screening of non-target compounds. The scan data are analysed using Deconvolution Reporting Software (DRS) which screens the results for 934 organic contaminants. Deconvolution helps identify contaminants that are buried in the chromatogram by co-extracted materials and significantly reduces chromatographic resolution requirements, allowing shorter analysis times. All compounds have locked retention times and we can continually update and extend the mass spectral library including new compounds. Linearity and limits of detection in SIM and full-scan mode were studied. Method detection limits (MDLs) in effluent wastewater ranged in most of the cases from 1 to 36 ng/L in SIM mode and from 4 to 66 ng/L in full-scan mode; while in river water from 0.4 to 14 and 2-29 ng/L in SIM and full-scan mode, respectively. We obtained a linearity of the calibration curves over two orders of magnitude. The method has been applied to the screening of a large number of organic contaminants--not only to a subset of targets--in urban wastewaters from different wastewater treatment plants and also in river waters. Most of the target compounds were detected at concentration levels ranging from 11 to 8697 ng/L and from 7 to 1861 ng/L in effluent wastewater and river waters, respectively. Additionally, a group of 12 new compounds were automatically identified using the AMDIS and NIST libraries. Other compounds, such as the 4-amino musk xylene, a synthetic fragrance metabolite, which was not included in the databases, but has been manually searched in the full-scan chromatograms.