Development and full validation of a multiresidue method for the analysis of a wide range of pesticides in processed fruit by UHPLC-MS/MS.

A reliable 16-min analytical method for the simultaneous determination of 250 pesticides in processed fruit using ultra-performance liquid chromatography, coupled to tandem mass spectrometry (UHPLC-MS/MS), was developed and validated according to SANTE 11813/2017 guidelines and accredited successfully based on ISO 17025. Extraction was achieved using a modified QuEChERS method, without any clean-up, including a dilution to obtain good peak shapes and to reduce matrix effects. Pesticides were quantified using matrix-matched calibration, and the method was validated in terms of relative retention time window, linearity (6-167 µg kg-1 and 0.6-16.7 µg kg-1, coefficient R2 ≥ 0.98), trueness (recovery of 70-120%), selectivity, precision (RSD ≤ 20%), limits of quantification (LOQs = 0.6-6.0 µg kg-1) and uncertainty. Finally, the method was applied to the routine analysis of 103 samples of processed fruits, detecting the presence of several pesticide residues, such as fluopyram, spinosad or cyprodinil (0.006-0.22 mg kg-1).

Actividad y concentraciones de antibióticos en muestras clínicas de pacientes con prostatitis crónica bacteriana / Antibiotic activity and concentrations in clinical samples from patients with chronic bacterial prostatitis

Objetivos: La prostatitis crónica bacteriana (PCB) es la enfermedad urológica más frecuente en menores de 50 años, cuya clínica de larga evolución puede estar relacionada con una inadecuada pauta terapéutica. El objetivo fue analizar la sensibilidad de los microorganismos aislados de pacientes con PCB y medir las concentraciones de antibiótico semanalmente en suero, semen y orina. Material y métodos: Para el estudio de la sensibilidad antibiótica, entre enero de 2013 y diciembre de 2014 se incluyeron 60 aislados clínicos procedentes de muestras de semen de pacientes confirmados microbiológicamente con PCB, y se llevó a cabo por microdilución en caldo. Para el estudio de las concentraciones de antibióticos, entre los meses de enero y mayo de 2014 se recogieron muestras de orina, sangre y semen, semanalmente, durante 4 semanas de tratamiento de 8 pacientes con cultivo positivo para PCB, y se midieron las concentraciones mediante cromatografía de líquidos de ultra alta eficacia acoplada a espectrometría de masas en tándem (UHPLC-MS/MS). Resultados: Fosfomicina y nitrofurantoína fueron los antibióticos con mayor actividad (95,2% en ambos casos). Las concentraciones medias de antibiótico en semen durante las 4 semanas estudiadas fueron las siguientes: 1,68 mg/l; 8,30 mg/l; 2,61 mg/l; 0,33 mg/l y 2,90 mg/l, respectivamente para los pacientes 1 a 5, que recibieron levofloxacino; 1,625 mg/l para el paciente 6, que recibió ciprofloxacino 2,67 mg/l para el paciente 7, que fue tratado con ampicilina, y 1,05 mg/l para el paciente 8, que recibió doxiciclina. Se obtuvieron mayores concentraciones en las muestras de orina que en suero y semen, siendo coparables estas 2 últimas. Conclusiones: Fosfomicina se postula como principal alternativa al tratamiento empírico de la PCB por su elevada actividad in vitro. La concentración de antibiótico en semen fue superior a la concentración mínima inhibitoria frente al agente etiológico, aunque no siempre se correlacionó la negativización microbiológica con la evolución clínica favorable

Objectives: Chronic bacterial prostatitis (CBP) is the most common urological disease in patients younger than 50 years, whose long-standing symptoms could be related to an inappropriate therapeutic regimen. The objective was to analyse the sensitivity of microorganisms isolated from patients with CBP and measure the weekly antibiotic concentrations in serum, semen and urine. Material and methods: For the antibiotic sensitivity study, 60 clinical isolates were included between January 2013 and December 2014 from semen samples from patients with microbiologically confirmed CBP. Broth microdilution was performed on the samples. For the antibiotic concentration study from January to May 2014, urine, blood and semen samples were collected weekly, over 4 weeks of treatment from 8 patients with positive cultures for CBP. The concentrations were measured using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Results: The antibiotics fosfomycin and nitrofurantoin had the highest activity (95.2% in both cases). The mean antibiotic concentrations in semen during the 4 weeks studied were as follows: 1.68 mg/L, 8.30 mg/L, 2.61 mg/L, 0.33 mg/L and 2.90 mg/L, respectively, for patients 1 to 5, who were treated with levofloxacin; 1.625 mg/L for patient 6, who was treated with ciprofloxacin; 2.67 mg/L for patient 7, who was treated with ampicillin; and 1.05 mg/L for patient 8, who was treated with doxycycline. Higher concentrations were obtained in the urine samples than in serum and semen, the latter 2 of which were comparable. Conclusions: Fosfomycin is proposed as the primary alternative to the empiric treatment of CBP due to its high in vitro activity. The antibiotic concentration in semen was higher than the minimal inhibitory concentration against the aetiological agent, although microbiological negativisation was not always correlated with a favourable clinical outcome

Solid phase microextraction and gas chromatography coupled to magnetic sector high resolution mass spectrometry for the ultra-trace determination of contaminants in surface water.

With the aim of monitoring water quality according to the regulations established by the European Union it would be necessary to implement analytical methodologies capable of simultaneously determining a broad range of organic pollutants at ultra-trace levels, allowing for increased sample throughput. In addition, the high number of samples to be analyzed requires a particular focus on setting up fully automated analytical methodologies. In view of that, this study is aimed at the development of a complete automated procedure for the ultra-trace determination of certain pesticides, polycyclic aromatic hydrocarbons (PAHs), brominated diphenyl ethers (BDEs) and polychlorinated biphenyls (PCBs) in surface waters. The proposed method is based on an on-line combination of solid phase microextraction (SPME) and gas chromatography coupled to double-focusing magnetic sector high resolution mass spectrometry (GC-HRMS). SPME as well as GC-HRMS conditions were optimized to achieve maximum extraction efficiency and sensitivity, which was reinforced by using multiple ion detection (MID) as acquisition mode. Using only 19mL of water and with minimum sample manipulation, the method allowed for the determination of 53 compounds exhibiting good linearity (R2>0.99), recoveries between 84 and 118% and relative standard deviation (RSD) values <20% for intra-day and inter-day precision. In addition, the method provides quantification limits (LOQs) between 0.1-50ngL-1, lower than the Environmental Quality Standards (EQS) fixed by Directive 2013/39/EC. Finally, the method was successfully applied to determine target contaminants in Almería surface water compartments, detecting dioxin-like PCBs, BDEs and some pesticides.

Antibiotic activity and concentrations in clinical samples from patients with chronic bacterial prostatitis. / Actividad y concentraciones de antibióticos en muestras clínicas de pacientes con prostatitis crónica bacteriana.

OBJECTIVES: Chronic bacterial prostatitis (CBP) is the most common urological disease in patients younger than 50 years, whose long-standing symptoms could be related to an inappropriate therapeutic regimen. The objective was to analyse the sensitivity of microorganisms isolated from patients with CBP and measure the weekly antibiotic concentrations in serum, semen and urine. MATERIAL AND METHODS: For the antibiotic sensitivity study, 60 clinical isolates were included between January 2013 and December 2014 from semen samples from patients with microbiologically confirmed CBP. Broth microdilution was performed on the samples. For the antibiotic concentration study from January to May 2014, urine, blood and semen samples were collected weekly, over 4 weeks of treatment from 8 patients with positive cultures for CBP. The concentrations were measured using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). RESULTS: The antibiotics fosfomycin and nitrofurantoin had the highest activity (95.2% in both cases). The mean antibiotic concentrations in semen during the 4 weeks studied were as follows: 1.68mg/L, 8.30mg/L, 2.61mg/L, 0.33mg/L and 2.90mg/L, respectively, for patients 1 to 5, who were treated with levofloxacin; 1.625mg/L for patient 6, who was treated with ciprofloxacin; 2.67mg/L for patient 7, who was treated with ampicillin; and 1.05mg/L for patient 8, who was treated with doxycycline. Higher concentrations were obtained in the urine samples than in serum and semen, the latter 2 of which were comparable. CONCLUSIONS: Fosfomycin is proposed as the primary alternative to the empiric treatment of CBP due to its high in vitro activity. The antibiotic concentration in semen was higher than the minimal inhibitory concentration against the aetiological agent, although microbiological negativisation was not always correlated with a favourable clinical outcome.

Simultaneous analysis of chlorophenols, alkylphenols, nitrophenols and cresols in wastewater effluents, using solid phase extraction and further determination by gas chromatography-tandem mass spectrometry.

An analytical methodology has been developed for the simultaneous extraction of 13 phenolic compounds, including chlorophenols (CPs), nitrophenols (NTPs), cresols and alkylphenols (APs) in different types of wastewater (WW) effluents. A solid-phase extraction (SPE) method has been optimized prior to the determination by gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS). Due to the complexity of the matrix, a comparison study of matrix-matched-calibration (MMC) and standard addition calibration (SAC) was carried out for quantification purposes. The optimized procedure was validated using the SAC approach since it provided the most adequate quantification results (in terms of recovery and precision values). Recoveries were in the range 60-135% (0.5 µg L(-1)), 70-115% (1 µg L(-1)), and 78-120% (5 µg L(-1)), with precision values (expressed as relative standard deviation, RSD) ≤ 30% (except for 2-nitrophenol) involving intra-day and inter-day precision studies. Limits of detection (LODs) and quantification (LOQs) were also evaluated, and LOQs ranged from 0.03 µg L(-1) to 2.5 µg L(-1). The proposed method was applied to the analysis of 8 real WW effluent samples, finding some phenolic compounds (e.g. 2-chlorophenol, 2,4,6-trichlorophenol and 4-tert-octylphenol) at concentrations higher than the established LOQs.

Simultaneous determination of pesticides, biopesticides and mycotoxins in organic products applying a quick, easy, cheap, effective, rugged and safe extraction procedure and ultra-high performance liquid chromatography-tandem mass spectrometry.

A method for the simultaneous determination of pesticides, biopesticides and mycotoxins from organic products was developed. Extraction of more than 90 compounds was evaluated and performed by using a modified QuEChERS-based (acronym of Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation procedure. The method was based on a single extraction with acidified acetonitrile, followed by partitioning with salts, avoiding any clean-up step prior the determination by ultra-high performance liquid chromatography/tandem quadrupole mass spectrometry (UHPLC-MS/MS). Validation studies were carried out in wheat, cucumber and red wine as representative matrixes. Recoveries of the spiked samples were in the range between 70 and 120% (with intra-day precision, expressed as relative standard deviation, lower than 20%) for most of the analysed compounds, except picloram and quinmerac. Inter-day precision, expressed as relative standard deviation, was lower than 24%. Limits of quantification were lower than 10µg kg⁻¹ and the developed method was successfully applied to the analysis of organic food products, detecting analytes belonging to the three types of compounds.

Determination of pesticide transformation products: a review of extraction and detection methods.

Pesticides are widely applied and they can produce a variety of transformation products (TPs), through different pathways and mechanisms. Nowadays there is a growing interest related to the determination of pesticide TPs in several matrices (environmental, food and biological samples), due to these compounds can be more toxic and persistent than parent compounds, and some of them can be used as markers of exposure to different pesticides. Although solid-phase extraction (SPE) is mainly used for the extraction of TPs, alternative techniques such as solid-phase microextraction (SPME) and liquid-phase extraction (LPE) can be used. These TPs are mainly determined by liquid chromatography (LC) due to the recent developments in this technique, especially when it is coupled to mass spectrometry (MS) detectors, allowing the determination of known and/or unknown TPs. Furthermore, MS is a very valuable tool for the structural elucidation of unknown TPs. This review discusses all phases of analytical procedure, including sample treatment and analysis, indicating the main problems related to the extraction of TPs from several matrices due to their high polarity, as well as the different alternatives found for the simultaneous determination of parent compounds and TPs, using chromatographic techniques coupled to MS detection.

Comparison of ultrasonic and pressurized liquid extraction for the analysis of polycyclic aromatic compounds in soil samples by gas chromatography coupled to tandem mass spectrometry.

A pressurized liquid extraction (PLE) method has been optimized for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil samples and it was compared with ultrasonic extraction. The extraction step was followed by gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS/MS) analysis. Parameters such as type of solvent, extraction time, extraction temperature and number of extractions were optimized. There were no significant differences among the two extraction methods although better extraction efficiencies were obtained when PLE was used, minimizing extraction time and solvent consumption. PLE procedure was validated, obtaining limits of detection (LODs) ranging from 0.02 to 0.75 microg kg(-1) and limits of quantification (LOQs) ranging from 0.07 to 2.50 microg kg(-1) for the selected PAHs. Recoveries were in the range of 59-110%, except for naphthalene, which was the most volatile PAH. Finally, the method was applied to real soil samples from Southeast of Spain. PAHs concentrations were low, and phenanthrene, pyrene, fluorene, benzo[a]pyrene and chrysene were the most frequently detected analytes in the samples.

Comparison of tandem-in-space and tandem-in-time mass spectrometry in gas chromatography determination of pesticides: application to simple and complex food samples.

Gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) is one of the most powerful techniques in pesticide residue analysis. MS/MS can be conceived in two ways: tandem in space (e.g. triple quadrupole, QqQ) or in time (e.g. ion trap, IT). QqQ and IT are commonly interfaced to GC; however, there has not been any direct comparison between them in pesticide residue analysis so far. In the present work, the performance of GC coupled to these two analyzers (GC-QqQ-MS/MS and GC-IT-MS/MS) was studied and compared for pesticide residue analysis as well as its application in food analysis. The large volume injection (LVI) technique together with programmed-temperature vaporization (PTV) was applied. For this purpose, 19 pesticides, including organochlorine and organophophorus pesticides and pyrethroids, were analyzed in both systems. Mass spectrometric data, performance characteristics (linearity, intra-day and inter-day precision) and the influence of the matrix nature on the analysis of low concentrations were compared. The target compounds were analyzed in solvent and in two representative food matrices such as cucumber (high water content) and egg (high fat content). MS data and intra-day precision were similar in QqQ and IT, whereas inter-day precision was significantly worse in QqQ. Linearity (expressed as determination coefficient, R(2)) in the range 10-150 microg L(-1) was adequate in both systems; however, better R(2) values were obtained with the QqQ analyzer in high and low concentration ranges (1-50 and 1-750 microg L(-1), respectively). The influence of the matrix nature on the analysis of low concentrations of each analyzer was also evaluated. The QqQ and IT performance was similar in cucumber and solvent. However, QqQ provided better sensitivity in egg working in selected reaction monitoring (SRM).

Multiresidue method for fast determination of pesticides in fruit juices by ultra performance liquid chromatography coupled to tandem mass spectrometry.

A new analytical method for the simultaneous determination of 90 pesticides in fruit juices by ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) has been developed and validated. Extraction was performed with acetonitrile, applying QuEChERS methodology, and the extracts were analyzed without any further clean-up step, providing better results than solid phase extraction (SPE) procedure. Before chromatographic step, extracts were diluted with water (1:1) in order to obtain good peak shapes. Several chromatographic conditions were evaluated in order to achieve a fast separation in Multiple Reaction Monitoring (MRM) mode, obtaining a run time of only 11 min. Matrix effect was studied for different types of fruit juices (peach, orange, pineapple, apple and multifruit), indicating that multifruit juice can be selected as representative matrix for routine analysis of these food commodities. Pesticides were quantified using matrix-matched calibration with recoveries between 70.4 and 108.5% and relative standard deviation lower than 20%. Limits of quantification were lower than 5 microg L(-1) in all the cases. The developed procedure was applied to commercial fruit juices, detecting carbendazim, cyprodinil and thiabendazol in a few samples.

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.

High-throughput determination of pesticide residues in food commodities by use of ultra-performance liquid chromatography-tandem mass spectrometry.

A rapid, simple, and sensitive multiresidue method for analysis of 53 pesticides in fruit and vegetables by ultra-performance liquid chromatography (UPLC) coupled to triple-quadrupole tandem mass spectrometry (MS-MS) has been developed and validated. Prior to analysis, analytes were extracted by use of buffered QuEChERS (quick, easy, cheap, effective, rugged, safe) methodology without further cleanup for non fatty matrices. Chromatographic conditions were optimised in order to achieve a fast separation in multiple reaction monitoring (MRM) mode. Indeed, more than 50 pesticides can be separated in less then 10 min. Four common representative matrices (cucumber, orange, strawberry, and olive) were selected to investigate the effect of different matrices on recovery and precision. Mean recoveries ranged from 70 to 109% with relative standard deviations lower than 20% for all the pesticides assayed in the four selected matrices. The method has been applied to the analysis of 200 vegetable samples, and imidacloprid was the pesticide most frequently found, with concentrations ranging from 0.01 to 1.00 mg kg(-1). This methodology combines the advantages of both QuEChERS and UPLC-MS-MS producing a very rapid, sensitive, and reliable procedure which can be applied in routine analytical laboratories.

Simultaneous determination of selected veterinary antibiotics in gilthead seabream (Sparus Aurata) by liquid chromatography-mass spectrometry.

A method was optimised and validated for simultaneous monitoring of several drugs of different classes of antibiotics such as quinolones (oxilinic acid and flumequine), tetracyclines (oxytetracycline), sulfonamides (sulfadiazine) and trimethoprim in fish muscle and skin. The method is based on solid-liquid extraction without further sample clean up followed by liquid chromatography-mass spectrometry (LC-MS) determination with electrospray ion source (ESI) in positive mode. The limits of quantification (LOQs) were lower than 20 microg/kg for all compounds and repeatability, expressed as relative standard deviations (RSD), were lower than 15%. Therefore, the LC-MS method was successfully applied for the quantitative determination of antibiotics in gilthead sea bream muscle and skin and oxytetracycline in medicated fishes.

Characterization of recovery profiles using gas chromatography-triple quadrupole mass spectrometry for the determination of pesticide residues in meat samples.

The assessment of the recovery factor with the analyte concentration in meat samples has been studied for the determination of organochlorine and organophosphorus pesticides in meat by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). For that purpose, recent IUPAC recommendations, which distinguishes between two terms, recovery factor and apparent recovery, have been followed. Besides, the systematic error due to the matrix effect has been evaluated by a new term recently proposed, calibration recovery. Recovery profiles were obtained analyzing spiked blank matrix, where the analytes were added before and after the extraction procedure. In a first step, the quantification of the compounds was carried out using a solvent calibration curve. The systematic errors due to the matrix effect during the quantification step and the error due to the sample treatment have been evaluated. Both apparent and calibration recovery components depend on the actual analyte concentration in the sample while the recovery factor remains constant except for analyte concentration close to quantification limit. In addition, the concentration limits, from which an acceptable recovery value (70-110%) can be obtained, are given. If spiked samples are quantified by matrix-matched calibration, the matrix effect is minimized and the calibration recovery component is 100%, and apparent recovery only depends on the recovery factor. The obtained values indicate recovery factor does not depend on the analyte concentration, except for those values closed to quantification limit.

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 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.

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.

Setting up of recovery profiles: A tool to perform the compliance with recovery requirements for residue analysis.

The use of the recovery term has presented some confusion in Analytical Chemistry. Recent IUPAC recommendations propose to distinguish between two terms: recovery or recovery factor, Re, and apparent recovery, Re*. Apparent recovery includes recovery factor and a new recovery term proposed in this paper, named calibration recovery, Re(C), which depends of the type of systematic error due to the matrix effect (constant and/or proportional) and is related to the applied calibration methodology. This paper highlights the dependence of the calibration recovery on the sample analyte concentration and, for extension, of the apparent recovery, defines the recovery profile, and makes evident the need to determine a "fit for purpose" analyte concentration interval to comply with a regulated recovery requirements. An approach to estimate the calibration recovery and its associated uncertainty in relation to the above-mentioned dependence is presented. The usefulness of the proposed methodology has been shown in the quantification of a pesticide by GC-ECD for assessing dermal exposure.

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.