A. Garrido Frenich

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.

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.

Wavelength selection method for multicomponent spectrophotometric determinations using partial least squares

A method for eliminating unnecessary wavelengths is applied with the goal of achieving improved prediction ability in multicomponent determinations by UV/VIS spectrophotometry with partial least squares (PLS). The feature selection method is based on the regression coefficients of the closed form of the PLS model. This method was evaluated with calibration data of different types, and with different criteria to choose the optimum number of factors. The results presented suggest that wavelength selection improves the prediction ability of PLS method.

Pesticide trace analysis using solid-phase extraction and gas chromatography with electron-capture and tandem mass spectrometric detection in water samples

Gas chromatography (GC) with electron-capture detection (ECD), mass spectrometry (MS) and tandem mass spectrometry (MS-MS) were employed for the identification of 12 pesticides in water samples. For this purpose, a solid-phase extraction procedure with C18 cartridges was used, optimising the breakthrough volume and the saturation concentration. In GC-MS-MS, the lowest detectable concentrations for the pesticides were between 2 and 26 ng l(-1), recoveries ranged from 70 to 133% in water samples spiked at 100 ng l(-1) and the relative standard deviations were in the range 5.3 to 17.4%. The proposed analytical methodology was applied to analyse pesticides in wetland samples from Almería (Spain).

Application of hollow fibre liquid phase microextraction for the multiresidue determination of pesticides in alcoholic beverages by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry

An alternative method has been developed to determine more than 50 pesticides in alcoholic beverages using hollow fibre liquid phase microextraction (HF-LPME) followed by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), without any further clean-up step. Pesticides were extracted from the sample to the organic solvent immobilized in the fibre and they were desorbed in methanol prior to chromatographic analysis. Experimental parameters related to microextraction such as type of organic solvent, extraction time and agitation rate have been optimized. The extraction method has been validated for several types of alcoholic beverages such as wine and beer, and no matrix effect was observed. The technique requires minimal sample handling and solvent consumption. Using optimum conditions, low detection limits (0.01-5.61microgL(-1)) and good linearity (R(2)>0.95) were obtained. Repeatability and interday precision ranged from 3.0 to 16.8% and from 5.9 to 21.2%, respectively. Finally the optimized method was applied to real samples and carbaryl, triadimenol, spyroxamine, epoxiconazole, triflumizol and fenazaquin were detected in some of the analyzed samples. The obtained results indicated that the new method can be successfully applied for extraction and determination of pesticides in alcoholic beverages, increasing sample throughput.

Application of the Kohonen neural network in coastal water management: methodological development for the assessment and prediction of water quality.

Kohonen neural network (KNN) was applied to nutrient data (ammonia, nitrite, nitrate and phosphate) taken from coastal waters in a Spanish tourist area. The activation maps obtained were not sufficient to evaluate and predict the trophic status of coastal waters. To achieve this aim, a new methodology is proposed which uses as its starting point the activation maps obtained from KNN. Firstly, to evaluate the trophic status of the coastal waters, it consists of the development of a quadrat system which enables a better classification than the traditional classification based simply on standardized data. The new classification allows clear differentiation of water quality within the mesotrophic band. Secondly, and in order to use the activation maps as predictive tools, the trophic classification, obtained from activation maps, was transposed onto new activation maps. To do this, the activation maps of the sampling points which defined each trophic group were superimposed. To avoid unnecessary complexity and to facilitate the process, this superimposition was undertaken only where the frequency exceeded 0.05. In this way, four frequency maps related to the trophic status of coastal waters (potentially eutrophic, high mesotrophic, low mesotrophic and oligotrophic) were obtained. There was no loss of relevant information in the new maps thus obtained. These frequency maps served as the basis for the successful prediction of the trophic status of random samples of coastal waters. This methodology, based on KNN, is proposed as a tool to aid the decision-making in coastal water quality management.

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.

Food contaminant analysis at high resolution mass spectrometry: Application for the determination of veterinary drugs in milk

Veterinary drugs (VDs) can remain in milk as a consequence of their use in livestock. In order to control the levels of VD residues in milk, screening methodologies can be applied for a rapid discrimination among negative and non-negative samples. In a second stage, non-negative samples are classified as negative or positive samples by using a confirmation method. Pre-target screening methods in low resolution MS (LRMS) are normally applied, but the number of analytes is limited, whereas the information obtained by full scan acquisition in high resolution mass spectrometry (HRMS) is improved. Here, three screening methods (running time<4 min) based on Orbitrap, quadrupole-time of flight (QqTOF) and triple quadrupole (QqQ) have been compared, using in all cases ultra-high performance liquid chromatography (UHPLC). For HRMS, the identification of the VDs was based on retention time (RT) and accurate mass measurements. Confirmation was based on the monitoring of fragments generated without precursor selection. The performance characteristics of the screening method provided reliable information regarding the presence or absence of the compounds below an established value, including uncertainty region and cut-off values. Better results in terms of cut-off values (≤ 5.0 μg kg(-1), except for spiramycin with a cut-off of 13.4 μg kg(-1) for milk samples and 43.1 μg kg(-1) for powdered milk based, emamectin with a cut-off of 42.2 μg kg(-1) for milk samples and doxycycline, with a cut-off value of 15.8 μg kg(-1) in powdered milk-based infant formulae) and uncertainty region were obtained using the Orbitrap-based screening method, which was submitted to further validation and used to analyze different real milk samples. The proposed method can be used in routine analysis, providing reliable results.

Determination of cypermethrin, fenvalerate and cis- and trans-permethrin in soil and groundwater by high-performance liquid chromatography using partial least-squares regression

Abstract The partial least-squares (PLS-2) method was applied to the simultaneous determination of the pyrethroids cypermethrin, fenvalerate and cis-trans -permethrin by HPLC. The PLS-2 method was also applied to the resolution of the ternary mixtures of cypermethrin, fenvalerate and trans -permethrin, cis -permethrin being determined from a calibration graph. The results obtained were compared and the best solution was applied to determine the four pyrethroids in soil and groundwater samples.