Spectrophotometric Method To Determine Ternary Mixtures of Atrazine, Diuron, and Chlorpyrifos in Water and Soil by a Ratio Spectrum-Zero Crossing Method

A spectrophotometric method based on simultaneous use of first derivative of ratio spectra and measurement of zero-crossing wavelengths resolves ternary mixtures of atrazine, diuron, and chlorpyrifos. Calibration graphs were linear for atrazine between 1 and 15 μg/mL and for diuron and chlorpyrifos between 1 and 10 μg/mL. The pesticides in groundwater and soil were determined by the method, at part-per-billion levels, after solidphase extraction, with good results. Interferences caused by other pesticides were studied.

Fast analysis of 4-tertoctylphenol, pentachlorophenol and 4-nonylphenol in river sediments by QuEChERS extraction procedure combined with GC-QqQ-MS/MS

A quick, easy, cheap, effective, rugged and safe (QuEChERS)-based extraction method has been optimized for the determination of pentachlorophenol, 4-tertoctylphenol and 4-nonylphenol in river sediments. The extraction method was followed by gas chromatography-triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) analysis, which ensures the reliable identification of the target compounds. The proposed method has been validated allowing the successful determination of the selected compounds, with recoveries ranging from 72 to 96%, when three concentration levels were evaluated (10, 50 and 100μgkg(-1)) and inter-day and intra-day precision, expressed as relative standard deviation (RSD), were lower than 20%. The method showed limits of detection (LODs) and limits of quantification (LOQs) ranging from 0.1 to 2.0μgkg(-1) and from 0.5 to 5.0μgkg(-1), respectively. Finally, 25 real samples from Poland have been analyzed, and only 4-tertoctylphenol was detected at concentrations up to 8.9μgkg(-1) of soil dry weight.

Assessment of ochratoxin A stability following gamma irradiation: experimental approaches for feed detoxification perspectives

The present study evaluated the effect of gamma irradiation on the stability of ochratoxin A (OTA) under various conditions. The effects of the physical state of OTA (solid vs aqueous), initial OTA concentration, irradiation dose and dose rate as well as the presence of model substances simulating food matrix compounds on OTA radiostability were investigated. First, pure OTA with and without food model compounds including α-D-glucose (monosaccharide), Methyl α-D-glucopyranoside (starch) and the amino acid derivatives N-α-acetyl-L-lysine methyl ester and N-α-acetyl-L-cysteine methyl ester (protein models) were irradiated with doses of 2, 4 and 8 kGy applied at 15.117 and 108.24 Gy/min. Secondly, artificially OTA-contaminated wheat with different moisture content (11, 14 and 16%) was irradiated with doses of 2, 4 and 8 kGy applied at 63.39 Gy/min. Residual OTA levels were analysed using ultra-high performance liquid chromatography coupled with tandem mass spectrometry. Solid OTA (50 and 3,200 ng/ml)showed great irradiation stability, even with irradiation doses up to 8 kGy. Under dry conditions, the presence of food model components did not affect OTA radiostability. However, in an aqueous solution, complete reduction was achieved at the initial OTA concentration of 50 ng/ml and irradiation dose of 2 kGy. Applying gamma irradiation to cereal-based food model systems produced a significant OTA reduction (5,000 µg/kg) of 47.2% in moistened wheat kernels (16%) with an absorbed dose of 8 kGy but failed to reduce the OTA content of low moisture content wheat (11%). These model experiments offered a useful tool to assess the main key factors affecting gamma irradiation-induced OTA reduction. Gamma irradiation is promising since the irradiation doses applied could partially reduce OTA contamination. Nevertheless, its efficacy was largely affected by initial moisture content and could be dangerous if toxic by-products are produced or nutritive quality is lost and needs further study.

Multiresidue method for the analysis of more than 140 pesticide residues in fruits and vegetables by gas chromatography coupled to triple quadrupole mass spectrometry

A new multiresidue method has been developed and validated for the determination of more than 140 pesticide residues in cucumber and orange by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS) in a single run of 25.50 min. The triple quadrupole (QqQ) analyzer simultaneously operated in the selected reaction monitoring (SRM) and selected ion monitoring (SIM) modes, acquiring two or three transitions per compound. Samples were extracted by the application of a single-phase extraction of 10 g of sample with acetonitrile containing 1% of acetic acid, followed by a liquid-liquid partition formed by the addition of 4 g of MgSO(4) and 1 g of NaOAc. A dispersive solid-phase extraction (D-SPE) with primary secondary amine (PSA) was applied to clean up the extracts. A final concentration step was included in order to increase sensitivity in the instrumental analysis. The method was properly validated in each matrix in a wide dynamic range (10-400 microg kg(-1)): this work relies on a new quantification strategy by the use of two calibration curves to increase the dynamic range, which permitted reduction of sample dilutions and increase in sample throughput. Recovery was studied at three concentration levels (11.5, 50.0, and 150.0 microg kg(-1)), yielding values in the range 70-110% with precision values, expressed as relative standard deviation (RSD), lower than 20 and 25% for the intraday and interday precision, respectively. Limits of quantification (LOQs) were established at 10 microg kg(-1), the lowest maximum residue level (MRL) value set by the European Union in vegetables. The method was successfully applied to the analysis of pesticide residues in real samples from the southeastern Spain.

Application of gas chromatography-triple quadrupole mass spectrometry in the quantification-confirmation of pesticides and polychlorinated biphenyls in eggs at trace levels

A new multiresidue method has been developed and validated for the simultaneous analysis of 57 compounds, including organochlorine and organophosphorus pesticide residues (OCPs and OPPs) and polychlorinated biphenyls (PCBs), in eggs at trace levels by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Egg samples were extracted by a simple and fast matrix solid phase dispersion (MSPD) procedure using C18 as sorbent, and ethyl acetate and acetonitrile saturated in n-hexane (85:15, v/v) as elution solvent with a simultaneous clean up with Florisil in-line. The QqQ analyzer acquired data in selected reaction monitoring (SRM) mode, permitting both quantification and confirmation in a single injection with a running time reduced up to 17.70 min. Recovery was in the range of 70-110% and 70-106% at 15 and 50 microg/kg, respectively. Precision values expressed as relative standard deviation (RSD) were lower than 20%. Linearity in the range of 10-150 microg/kg provided determination coefficients (R(2)) higher than 0.98 for all compounds. Limits of detection (LODs) for pesticides were < or =2.25 microg/kg and limits of quantification (LOQs) ranged from 0.02 to 7.78 microg/kg. LODs for PCBs were < or =0.41 microg/kg and LOQ were < or =0.71 microg/kg. The method was applied to real samples. Endosulfan sulphate and p,p'-DDE were found in two samples at concentrations below the first calibration level.

Assessment of butyltin and phenyltin pollution in the sea mullet, Mugil cephalus, along the Moroccan and Spanish coasts (Mediterranean Sea)

Levels of three butyltin (BTs) compounds, monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT), and three phenyltin (PTs) compounds, monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TPhT), were determined in the sea mullet, Mugil cephalus, collected along the northern Mediterranean coast of Morocco, and the south Mediterranean coast of Spain. Also, sediment samples from the Guadalquivir River (Spain) near to its mouth in the Mediterranean Sea were analysed. TBT and TPhT were the predominant compounds in the analyzed samples, and TBT concentrations were higher in liver than in muscle. In general, the total content of BTs in these samples was higher than PT levels. In the Moroccan coast, the highest value of BTs (18.00 mg/Kg wet weight) was found in the west harbour of the Tangier site, while the lowest concentration (0.01 mg/Kg wet weight) was detected in the Oued Laoue site. Concerning PTs compounds, the highest value (4.00 mg/Kg wet weight) was found in the harbour of the M'diq Site and the lowest value (0.01 mg/Kg wet weight) was detected in the Oued Laoue site. On the other hand, organotin (OT) residues were not detected in the water samples of the Spanish coast although TBT was identified in four of the nine sediment samples from the Guadalquivir River at concentrations between 15.45 and 245.07 mg/Kg wet weight.

Determination of polycyclic aromatic hydrocarbons in olive oil by a completely automated headspace technique coupled to gas chromatography-mass spectrometry

A new and completely automated method for the determination of ten relevant polycyclic aromatic hydrocarbons (PAHs) in olive oil is proposed using an extraction by the headspace (HS) technique. Quantification and confirmation steps are carried out by gas chromatography-mass spectrometry (GC-MS) combining simultaneously selected-ion monitoring (SIM) and tandem mass spectrometry (MS/MS). This combination offers on one hand an increased sensitivity and on the other hand, selective and reliable qualitative information. Sample pretreatment or clean-up are not necessary because the olive oil sample is put directly into an HS vial, automatically processed by HS and introduced into the GC-MS instrument for analysis. Because of its high selectivity and sensitivity, a triple-quadrupole (QqQ) detector coupled with the gas chromatograph allows us to limit handling. Each sample is completely processed in approximately 63 min (45 min for HS isolation and 18 min for GC-MS determination), a reduced time compared with previously published methods. The chemical and instrumental variables were preliminarily optimized using uncontaminated olive oil samples spiked with 25 microg kg(-1) of each target compound. The final method was validated to ensure the quality of the results. The precision was satisfactory, with relative standard deviation (RSD) values in the range 3-9%. Recovery rates ranged from 96 to 99%. Limits of detection (LOD) were calculated as 0.02-0.06 microg kg(-1) and the limits of quantification (LOQ) were obtained as 0.07-0.26 microg kg(-1). It must be mentioned that the LOD and LOQ are much lower than the maximum levels established by the European Union (EU) in oils and fats intended for direct human consumption or for use as an ingredient in foods, which are set at 2 microg kg(-1). All the figures of merit are completely in accordance with the latest EU legislation. This fact makes it possible to consider the proposed method as a useful tool for the control of PAHs in olive oils.

Evaluation of different sample treatments for determining pesticide residues in fat vegetable matrices like avocado by low-pressure gas chromatography–tandem mass spectrometry

A multi-residue method has been developed for determining 65 pesticide residues in greasy vegetable matrices such as avocado. Conventional organic solvent extraction assisted by a high-speed homogenizer was compared to pressurized liquid extraction (PLE) as extraction techniques. Following this, the lipophilic extract was purified using gel permeation chromatography (GPC). Alternative clean-up methods were also evaluated, as solid-phase extraction cartridges individually used and downstream coupled, but less effective lipophilic separation was archived. The pesticide residue determination was carried out using low-pressure gas chromatography coupled to tandem mass spectrometry (LP-GC-MS-MS), showing the applicability of this type of GC columns for the analysis of fat vegetable matrices. The proposed methodology was validated in avocado matrix. The recoveries were in the range 70-110%, with RSD values lower than 19%, at 12 and 50 microg/kg spiking levels. The limits of quantitation (LOQs) were in the range 0.04-8.33 microg/kg and the limits of detection (LODs) were between 0.01 and 2.50 microg/kg. All of them were lower than the maximum residue levels (MRLs) set by the European Union (EU) in avocado. The proposed method was evaluated analyzing pesticide residues in real avocado samples.

Validation of a gas chromatography/triple quadrupole mass spectrometry based method for the quantification of pesticides in food commodities

A new multiresidue method has been validated in cucumber matrix for the routine analysis of 130 multiclass pesticide residues by gas chromatography/triple quadrupole mass spectrometry. The pesticides were extracted with ethyl acetate. A first identification of the pesticides was based on a tandem mass spectrometric (MS/MS) screening method, which monitors a single transition for each target compound, in less than 12 min. After that, potentially non-negative samples were analyzed again by the MS/MS confirmation/quantification method, which monitors two or three MS/MS transitions for each compound, also in less than 12 min. Performance characteristics, such as trueness, precision, linear range, detection limit (LOD) and quantification limit (LOQ), for each pesticide were calculated. The average recoveries obtained ranged between 70 and 120% at three different fortification levels (25, 200 and 500 microg/kg) with precision, expressed as relative standard deviation (RSD), values lower than 15%. The calculated LOD and LOQ were typically <3.2 and 9.6 microg/kg, respectively. Such limits were much lower than the maximum residue levels (MRLs) established by European legislation. The proposed methodology was applied to the determination of pesticides in real vegetable samples from Almería (Spain).

Determination of multiclass pesticides in food commodities by pressurized liquid extraction using GC–MS/MS and LC–MS/MS

Pressurized liquid extraction (PLE) was applied to the simultaneous extraction of a wide range of pesticides from food commodities. Extractions were performed by mixing 4 g of sample with 4 g of Hydromatrix and (after optimization) a mixture of ethyl acetate:acetone (3:1, v/v) as extraction solvent, a temperature of 100 degrees C, a pressure of 1000 psi and a static extraction time of 5 min. After extraction, the more polar compounds were analyzed by liquid chromatography (LC), and the apolar and semipolar pesticides by gas chromatography (GC); in both cases LC and GC were coupled with mass spectrometry in tandem (MS/MS) mode. The overall method (including the PLE step) was validated in GC and LC according to the criteria of the SANCO Document of the European Commission. The average extraction recoveries (at two concentration levels) for most of the analytes were in the range 70-80%, with precision values usually lower than 15%. Limits of quantification (LOQ) were low enough to determine the pesticide residues at concentrations below or equal to the maximum residue levels (MRL) specified by legislation. In order to assess its applicability to the analysis of real samples, aliquots of 15 vegetable samples were processed using a conventional extraction method with dichloromethane, and the results obtained were compared with the proposed PLE method; differences lower than 0.01 mg kg(-1) were found.

Determination of ascorbic acid and carotenoids in food commodities by liquid chromatography with mass spectrometry detection

Two methods, one to determine ascorbic acid and one to determine lycopene and beta-carotene, in vegetables and fruits by liquid chromatography coupled with mass spectrometry (LC-MS) have been established. The chromatographic separation of the studied compounds and their MS parameters were optimized to improve selectivity and sensitivity. In both methods, separation was carried out with two coupled columns, first a C(18) and then a dC(18), using as mobile phase 70% methanol (0.005% acetic acid) and 30% acetic acid 0.05% for ascorbic acid determination and a mixture of methanol, tetrahydrofuran, and acetonitrile (60:30:10 v/v/v) for carotenoid analysis in isocratic mode. The molecular ion was selected for the quantification in selective ion monitoring (SIM) mode. Ascorbic acid was detected with electrospray ionization probe (ESI) in negative mode, while chemical ionization atmospheric pressure (APCI) in positive mode was used for the target carotenoids. The methodology for ascorbic acid analysis is based on an extraction with polytron using methanol and a mixture of methaphosphoric acid and acetic acid. Extraction of the carotenoids was carried out with tetrahydrofuran/methanol (1:1) (v/v). The proposed methods were applied, after their corresponding validations, to the analysis of four varieties of tomatoes, tomato in tin enriched and dried tomato, and to the analysis of mango and kiwi fruits, to compare the content in these compounds. Moreover, the influence of the process of freezing and the effect that the manipulation/preservation has in the content of ascorbic acid in tomato have also been studied.

A study of the disappearance of pesticides during composting using a gas chromatography-tandem mass spectrometry technique

A simple method for multi-residue analysis of pesticides by low-pressure gas chromatography-tandem mass spectrometry (LP-GC-MS-MS) has been validated in compost samples. The pesticide residues were extracted from the lyophilised samples with organic solvent by stirring. No sample clean-up was required prior to the analysis. The method was applied to determine the fate of two organochlorine pesticides (lindane and endosulfan) and two organophosphates (malathion and chlorpyrifos-methyl) during the composting process in the reactor of a pilot plant. Malathion, chlorpyrifos-methyl and lindane residues almost fully disappeared after 8 days of maturation in the reactor, while endosulfan residues were only partially degraded. Alongside this, a study of natural disappearance of the pesticides was carried out in the laboratory and a characteristic time profile was traced for each pesticide class.

Determination of pesticides and some metabolites in different kinds of milk by solid-phase microextraction and low-pressure gas chromatography-tandem mass spectrometry

A new analytical method is proposed to determine more than 40 multiclass pesticides in different kinds of processed (whole, skimmed and powdered) and unprocessed (goat and human) milk samples using solid-phase microextraction (SPME). A comparative study between headspace (HS) and direct immersion (DI) was carried out. The effect of milk dilution and the use of acid to reduce the influence of the matrix in DI-SPME mode were also evaluated. DI of the SPME fiber into previously diluted and acidified milk samples achieved the best sensitivity results. Pesticides were determined using low-pressure gas chromatography-tandem mass spectrometry (LP-GC-MS/MS). Both of the selected techniques have been shown to be effective at reduce fat interference and can determine analytes present at very low concentrations (limits of quantification between 0.02 and 1.00 microg L(-1)). Performance characteristics such as linearity, recovery, precision, and lower limits, together with an estimation of the measurement uncertainty using validation data, are presented for each pesticide. All of the pesticides presented recovery rates of between 81 and 110% and precision values lower than 12% (expressed as the relative standard deviation). The overall uncertainty of the method was estimated at three different concentrations (10, 25 and 50 microg L(-1)) and was lower than 25.5% in all cases. The proposed analytical methodology was applied to the analysis of target pesticides in 35 samples: 15 commercial, 3 human and 17 goat milk samples. The metabolite p,p'-DDE was the compound most frequently found in both the breast and goat milk samples, at concentration levels < 20 microg L(-1). However, pesticide residues were not found in any of the other 15 commercial milk samples (skimmed, powdered and whole milk) analyzed.

Application of internal quality control to the analysis of quaternary ammonium compounds in surface and groundwater from Andalusia (Spain) by liquid chromatography with mass spectrometry

A method has been developed for the simultaneous determination of paraquat (PQ), deiquat (DQ), chlormequat (CQ) and mepiquat (MQ) in water samples by liquid chromatography (LC) coupled with electrospray ionization mass spectrometry (MS). The LC separations of the target compounds, as well as their MS parameters, were optimized in order to improve selectivity and sensitivity. Separation was carried out in a Xterra C8 column, using as mobile phase methanol-heptafluorobutyric acid (HFBA) in isocratic mode. The molecular ion was selected for the quantitation in selected ion monitoring (SIM) mode. Off-line solid-phase extraction (SPE) was applied with silica cartridges in order to preconcentrate the compounds from waters. Detection limits were in the range 0.02-0.40 microg l(-1). Recovery range varied between 89 and 99.5% with precision values lower than 6%. The method has been applied successfully to the analysis of both surface and groundwater samples from agricultural areas of Andalusia (Spain), using well defined internal quality control (IQC) criteria. The results revealed the presence of deiquat and paraquat in some samples.

Monitoring multi-class pesticide residues in fresh fruits and vegetables by liquid chromatography with tandem mass spectrometry

A new analytical method was developed using liquid chromatography with tandem mass spectrometry for the routine analysis of 31 multi-class pesticide residues and applied to approximately 50 fresh fruit and vegetable samples (green bean, cucumber, pepper, tomato, eggplant, watermelon, melon and zucchini). Extraction of the pesticides with ethyl acetate was carried out. The optimal ionisation conditions were selected for each pesticide in the same run. The procedure was validated and the values of some merit figures, such as recovery, precision, linear range, detection limit and quantification limit for each pesticide were calculated together with its calculated expanded uncertainty (U). The average recoveries in cucumber obtained for each pesticide ranged between 74 and 105% at two different fortification levels (n = 10 each) that ranged between 9 and 250 ng g(-1) (depending on the pesticide). The uncertainty associated to the analytical method was lower than 23% for all compounds tested. The calculated limits of detection and quantitation were typically <1 ng g(-1) that were much lower than the maximum residue levels established by European legislation.

Single step determination of fragrances in Cucurbita flowers by coupling headspace solid-phase microextraction low-pressure gas chromatography–tandem mass spectrometry

Coupling headspace solid-phase microextraction (HS-SPME) and low-pressure gas chromatography-tandem mass spectrometry (LP-GC-MS-MS) has been used for determining 20 volatile compounds present in flowers. HS-SPME coupled with LP-GC-MS-MS acts in a synergic way allowing a fast extraction and analysis of the target compounds. The method has been optimised studying the influence of the adsorption temperature and adsorption time. The best results were obtained heating the SPME vials at 60 degrees C for 5 min using 65 microm poly(dimethylsiloxane-divinylbenzene) fibers. The validation of the method ensures the fitness for the purpose of the analytical method, achieving appropriate lower limits, recoveries and precision. The analytical method has been applied to the characterisation of zucchini flowers fragrances in air using passive sampling, in order to improve our knowledge on zucchini fragrances and to better pollination technique in future steps.

Determination of fifteen priority phenolic compounds in environmental samples from Andalusia (Spain) by liquid chromatography?mass spectrometry

This work describes the optimisation of a method to determinate fifteen phenolic compounds in waters, sediments and biota (green marine algae) by liquid chromatography coupled to mass spectrometry (LC-MS) with atmospheric pressure chemical ionisation (APCI) in the negative mode. The LC separations of the studied compounds and their MS parameters were optimised in order to improve selectivity and sensitivity. Separation was carried out with a C(18) column using methanol and 0.005% acid acetic as mobile phase in gradient mode. The molecular ion was selected for the quantitation in selective ion monitoring (SIM) mode. A solid-phase extraction (SPE) method was applied in order to preconcentrate the target analytes from water samples. However, extraction of the compounds from sediment and biota samples was carried out by liquid-solid extraction with methanol/water after studying the influence of other organic solvents. In addition, a clean-up step by SPE with HLB Oasis cartridges was necessary for sediments and biota. The proposed analytical methodology was validated in the target environmental matrices by the analysis of spiked blank matrix samples. Detection limits were 10-50 ng L(-1) for water, 1-5 microg kg(-1) for sediments and 2.5-5 microg kg(-1) for biota samples. Good recoveries and precision values were obtained for all matrices. This methodology has been successfully applied to the analysis of incurred water, sediment and biota samples from Andalusia (Spain).

Assessment of potential (inhalation and dermal) and actual exposure to acetamiprid by greenhouse applicators using liquid chromatography–tandem mass spectrometry

New analytical methods based on liquid chromatography with electrospray tandem mass spectrometry (LC-MS/MS) have been developed and validated for assessing the exposure of greenhouse workers to acetamiprid. Both ambient (potential inhalation and dermal exposure) and internal dose (biological monitoring of urine samples) measurements were carried out. Potential inhalation exposure was assessed using Chromosorb 102 cartridges connected to air personal samplers. Potential dermal exposure was estimated by using whole body dosimetry. The measurement of actual exposure was done by analyzing the parent compound in urine samples of the applicators, after a solid-phase extraction (SPE) step. The methods showed a good accuracy (72-92%), precision (2-13%) and lower limits (few microg l(-1)). The validated approaches have been applied to assess potential and actual exposure of agricultural workers spraying acetamiprid in greenhouses. The results shown the need to wear personal protective equipment (suits) in order to reduce the absorbed dose of acetamiprid.

Assessment of metal contamination in Doñana National Park (Spain) using crayfish (Procamburus clarkii)

Water quality assessment in the Aznalcollar area was attempted using multivariate methods based on heavy metal concentrations in red swamp crayfish (Procamburus clarkii). Trace levels of four heavy metals, copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb), were detected in crayfish from eleven different stations. Principal component analysis (PCA) highlighted a gradient of contamination between the sampling stations. Cluster analysis (CA) distinguished three groups of stations. Discriminant analysis also differentiated three groups. The group centroids of the first discriminant function were used to devise an index that varies according to the source of the crayfish. These standardized values are proposed for use as a water quality index. The ability of this index to successfully predict environmental quality was proved with random samples.

Screening method for pesticides in air by gas chromatography/tandem mass spectrometry

A multiresidue method for determining more than 70 pesticides in air has been validated using a single injection with gas chromatography/tandem mass spectrometry (GC/MS/MS). The method validation considered both stages of sampling and analysis. The sampling method, based on active sampling using sorption in sorbent cartidges, was validated by generating standard atmospheres. Performance parameters of the method were evaluated, with a reduction in the limits of quantification by injecting a higher volume of sample extract, and increase of selectivity by the use of MS/MS detection mode. The method was based on solid-phase extraction, which permits a degree of automation. The best adsorbents were found to be Chromosorb 106 and Tenax TA. The retention capacity of these sampling sorbents allows up to 1440 L of air to be sampled without any breakthrough for most of the compounds. Data were generated for assessing the potential exposure of bystanders. The application of the method to the analysis of the air in urban locations near agricultural areas showed that pesticides were present in most of the samples.

Application of GRAM and TLD to the resolution and quantitation of real complex multicomponent mixtures by fluorescence spectroscopy

The application of the generalised rank annihilation method (GRAM) and the trilinear decomposition (TLD) method to the resolution and quantitation of fluorescence excitation-emission matrices of a ternary mixture of pesticides, carbendazim, fuberidazole, and thiabendazole, with overlapped spectra is described. The results obtained with both methods are compared and evaluated using measures of similarity (correlation coefficients) between the real and estimated spectra. Both approaches have been tested using augmented data matrices containing only two samples, but none of these methods succeeded completely in resolution of the system. When TLD was applied to augmented data matrices containing more than two samples better performance was achieved. To illustrate the application of both algorithms to real samples, they were used in the analysis of water samples containing the target pesticides. Again, TLD had an advantage over GRAM because the ability to analyse data from multiple (more than two) samples simultaneously allowed the resolution of the mixtures.

Trace determination of organotin compounds in water, sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).

Dermal exposure to pesticides in greenhouses workers: discrimination and selection of variables for the design of monitoring programs

Dermal exposure to pesticides is one of the main sanitary problems which greenhouses workers face. With the dual aims of establishing both the body part that receives the greatest exposure and the variable that has greatest influence on this exposure level, 22 pesticide application trials were performed. Trials were carried out in different greenhouse vegetable crops, using different pesticides and different spray diameters from the spray gun. In order to determine dermal exposure, the whole body method was used. Pieces of the applicator suit were subject to an extraction procedure and their pesticide content determined using GC-NPD analysis. Multivariate analysis were applied to the data obtained. Principal component analysis showed that all trials produced a high exposure level on lower left leg and lower right leg. Cluster analysis distinguished between three sample groups. The most and the least affected parts were clearly distinguished. Discriminant analysis indicated that the thin drop size of the spray gun is responsible for both the differences between groups and the minimum or maximum exposure level measured on the applicator suit. Therefore, selecting the variables, lower legs and thin drop size, is considered fundamental in designing programs for monitoring pesticide exposure.