Single solid phase extraction method for the simultaneous analysis of polar and non-polar pesticides in urine samples by gas chromatography and ultra high pressure liquid chromatography coupled to tandem mass spectrometry.

A new multiresidue method has been developed and validated for the simultaneous extraction of more than two hundred pesticides, including non-polar and polar pesticides (carbamates, organochlorine, organophosphorous, pyrethroids, herbicides and insecticides) in urine at trace levels by gas and ultra high pressure liquid chromatography coupled to ion trap and triple quadrupole mass spectrometry, respectively (GC-IT-MS/MS, UHPLC-QqQ-MS/MS). Non-polar and polar pesticides were simultaneously extracted from urine samples by a simple and fast solid phase extraction (SPE) procedure using C(18) cartridges as sorbent, and dichloromethane as elution solvent. Recovery was in the range of 60-120%. Precision values expressed as relative standard deviation (RSD) were lower than 25%. Identification and confirmation of the compounds were performed by the use of retention time windows, comparison of spectra (GC-amenable compounds) or the estimation of the ion ratio (LC-amenable compounds). For GC-amenable pesticides, limits of detection (LODs) ranged from 0.001 to 0.436 µg L(-1) and limits of quantification (LOQs) from 0.003 to 1.452 µg L(-1). For LC-amenable pesticides, LODs ranged from 0.003 to 1.048 µg L(-1) and LOQs ranged from 0.011 to 3.494 µg L(-1). Finally, the optimized method was applied to the analysis of fourteen real samples of infants from agricultural population. Some pesticides such as methoxyfenozide, tebufenozide, piperonyl butoxide and propoxur were found at concentrations ranged from 1.61 to 24.4 µg L(-1), whereas methiocarb sulfoxide was detected at trace levels in two samples.

Determination of 19 volatile organic compounds in wastewater effluents from different treatments by purge and trap followed by gas-chromatography coupled to mass spectrometry.

A rapid and simple methodology based on purge and trap with gas-chromatography coupled to triple quadrupole mass spectrometry has been developed for the analysis of 19 volatile organic compounds (VOCs) in wastewater (WW) effluents from four different treatments. The determination was carried out in the raw WW effluents, which were not submitted to any pre-treatment (e.g., filtration). A matrix effect study was also performed, concluding that solvent calibration was adequate to quantify VOCs in WW effluent samples containing a variety of suspended particulate matter. Adequate validation parameters were obtained with recovery values in the range 73-124% and precision values lower than 24%. Limits of quantification were established at 0.1 µg L(-1) for all VOCs. The proposed method was applied to the analysis of WW samples, detecting chloroform and toluene at concentrations ranging from 0.1 to 4.80 µg L(-1).

Comprehensive analysis of polycyclic aromatic hydrocarbons in wastewater using stir bar sorptive extraction and gas chromatography coupled to tandem mass spectrometry.

The objective of this study was the optimization and comparison of two extraction methods for the determination of polycyclic aromatic hydrocarbons (PAHs) in wastewater (WW). A distribution study of the target compounds between the aqueous phase and the suspended particulate matter (SPM) has been performed in order to establish whether the analysis of both phases is necessary. In this sense, the feasibility of stir bar sorptive extraction (SBSE) and solid-phase extraction (SPE) for the determination of 24 PAHs in WW samples has been evaluated. The results demonstrated the suitability of SBSE to perform a comprehensive analysis of liquid samples containing high amounts of SPM, such as in the determination of PAHs in WWs. A gas chromatography triple quadrupole mass spectrometry (GC-QqQ-MS/MS) method has been also optimized for the separation and detection of the target compounds, avoiding the co-elution of some groups of isomers, such as benzo[b], [j] and [k] fluoranthenes and indene[1,2,3-cd]pyrene/dibenz[a,h]anthracene. For that purpose, a specific capillary column developed for PAH determination was used. The SBSE procedure was validated and adequate parameters (such as recovery, linearity, precision, limits of detection and quantification) were obtained. Finally, the validated method was applied to the analysis of real samples collected from an experimental WW treatment plant, detecting some PAHs at concentrations in the range 0.007-0.022 µg L(-1).

Compensation for matrix effects in gas chromatography-tandem mass spectrometry using a single point standard addition.

One of the major problems in quantitative analysis of pesticide residues in food samples by gas chromatography-tandem mass spectrometry (GC-MS/MS) is the enhancement or the suppression, of the target analyte signals in matrix extracts. Potentially positive samples, which had previously been identified by a rapid screening method, were quantified using standard addition to compensate matrix effects. As example we performed a systematic study on the application of the standard addition calibration (SAC) method for the determination of 12 pesticides (acephate, bromopropylate, chlorpyrifos, cypermethrin, diazinon, etrimfos, heptenophos, iprodione, methamidophos, procymidone, tetradifon, and triadimefon) in two matrices (cucumber and orange) in the range of initial concentrations of 10-200 microg kg(-1). The influence of some factors, such as the minimum number of standard additions used (single, two, three or four points calibration), as well as the known amount of analyte added to the sample, is evaluated in order to obtain reliable results. Accurate quantification is achieved when a single point SAC at 200 microg kg(-1) was used, obtaining for all the cases recoveries between 70 and 120%. The proposed analytical approach only needs two injections per sample (blank and spiked extracted sample) to determine the final concentration of pesticide in positive 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.

Empleo de la espectrometría de masas como herramienta para la determinación de tóxicos en alimentos: hacia la seguridad alimentaria / Using mass spectrometry as a tool for testing for toxic substances in foods: toward food safety

En los alimentos se pueden encontrar un gran número desustancias tóxicas, tales como plaguicidas, antibióticos y toxinas,presentando distintos orígenes (naturales o sintéticos) yniveles de toxicidad para la salud humana. Este tipo de compuestosse encuentran generalmente a muy bajas concentracionesen matrices muy complejas, por lo que es necesario la utilizaciónde metodologías lo más fiables posibles. En estesentido, el empleo de las técnicas cromatográficas (de gases yde líquidos) acopladas a detectores de espectrometría de masasha permitido la detección adecuada de este tipo de sustanciasen los alimentos a concentraciones extremadamente bajas. Porello, y en función de las características del contaminante, sedebe elegir la técnica cromatográfica que posibilite una mejorseparación del contaminante de los interferentes presentes enla matriz, así como de los contaminantes entre sí. Esta metodologíaproporciona datos de gran valor que mejoran nuestroconocimiento de la Salud Pública a través de la Seguridad Alimentaria(AU)

A large number of toxic substances, such as pesticides,antibiotics and toxins from different sources (natural or manmade)and different degrees of toxicity for human health canbe found in foods. This type of compounds are generally foundat very low concentrations in highly complex matrices, ittherefore being necessary for the most highly reliablemethodologies possible to be sued. In this regard, the use ofgas and liquid chromatography techniques coupled to massspectrometry detectors has made it possible to properly detectthis type of substances in foods at extremely lowconcentrations. Therefore, depending upon the characteristicsof the contaminant, one must select the chromatographytechnique which affords the possibility of best separating thecontaminant from the interfering substances present in thematrix, as well as from the contaminants amongst one another.This methodology provides highly valuable data enhancingour knowledge of Public Health through Food Safety(AU)

Application of gas chromatography coupled to triple quadrupole mass spectrometry for the multiresidue analysis of pesticides in olive oil.

A new multiresidue method has been developed and validated for the simultaneous determination of 100 pesticide residues in olive oil. The determination of pesticide residues was carried out in only 19 min by gas chromatography coupled to tandem mass spectrometry using a triple quadrupole mass analyzer. The mass spectrometer was operated in electron ionization and the selection reaction monitoring mode was used, acquiring two or three fragmentation reactions per compound. Two extraction processes were studied, and an evaluation of the stability and sensitivity of the chromatographic system has been performed for the tested extraction procedures. The final proposed methodology was based on a liquid-liquid partition with an n-hexane/acetonitrile mixture followed by a gel permeation chromatography cleanup step. An adequate lineal relation was obtained in the studied concentration range (10-200 microg kg (-1)); the recovery values were in the range 70-110% for the two levels of concentration studied: 12 and 50 microg kg (-1). Precision values, expressed as relative standard deviation, were lower than 18% at the aforementioned spiking levels; detection limits, confirmation limits, and quantitation limits were below or equal to 1.9, 2.6, and 3.6 microg kg (-1), respectively. The developed methodology was applied to the analysis of pesticide residues in real samples of olive oil from the south of Spain.

Application of low-pressure gas chromatography/tandem mass spectrometry to the determination of pesticide residues in tropical fruits.

A multiresidue method has been developed for determining pesticide residues in the tropical fruits kiwi, custard apple, and mango. The intended purpose of the method is for regulatory analyses of commodities for pesticides that have established maximum residue limits. A fast and simple extraction method with cyclohexane-ethyl acetate (1 + 1, v/v) and a high-speed homogenizer was optimized. Pressurized liquid extraction was evaluated as an alternative automated extraction technique. The pesticide residues were determined by using low-pressure gas chromatography coupled to tandem mass spectrometry. The proposed methodology was validated for each matrix. Pesticide recoveries ranged from 70 to 110%, with repeatability relative standard deviations of < or = 18% at spiking levels of 12 and 50 microg/kg. The limits of quantitation were in the range of 0.03-6.17 microg/kg, and the limits of detection were between 0.01 and 3.75 microg/kg. Mango can be selected as a representative matrix for calibration on the basis of the results of a potential matrix effect study. The method was successfully applied to the determination of pesticide residues in real samples in Spain.

[Using mass spectrometry as a tool for testing for toxic substances in foods: toward food safety]. / Empleo de la espectrometría de masas como herramienta para la determinación de tóxicos en alimentos: hacia la seguridad alimentaria.

A large number of toxic substances, such as pesticides, antibiotics and toxins from different sources (natural or man-made) and different degrees of toxicity for human health can be found in foods. This type of compounds are generally found at very low concentrations in highly complex matrices, it therefore being necessary for the most highly reliable methodologies possible to be sued. In this regard, the use of gas and liquid chromatography techniques coupled to mass spectrometry detectors has made it possible to properly detect this type of substances in foods at extremely low concentrations. Therefore, depending upon the characteristics of the contaminant, one must select the chromatography technique which affords the possibility of best separating the contaminant from the interfering substances present in the matrix, as well as from the contaminants amongst one another. This methodology provides highly valuable data enhancing our knowledge of public health through food safety.