Monitoring of pesticide residues in dairy cattle farms from NW Spain.

The consequences of the use of pesticides in agricultural activities for food and feed product safety are subjects of major concern. In the present work, simple and environmentally friendly methodologies were applied to the analysis of soil and cattle feed samples collected in dairy cattle farms from Galicia (NW Spain). This forms part of an integrated study aiming to investigate the global impact of the use of pesticides in such farms. The target compounds were 36 plant protection products belonging to different families. Organochlorine and organophosphorus pesticides were the most commonly detected compounds in the analyzed samples; pyrethroid and chloroacetanilide pesticides were also found in some of them, but not so frequently. Detected levels were rarely above the established legal limits.

Validation of an off line solid phase extraction liquid chromatography-tandem mass spectrometry method for the determination of systemic insecticide residues in honey and pollen samples collected in apiaries from NW Spain.

The use of pesticides to protect crops against plagues and insects is one of the most important ways to assure agricultural quality and productivity. However, bad application practices may cause the contamination of different environmental compartments and animal species, as a consequence of migration or accumulation of those compounds. Fipronil, imidacloprid and thiametoxam are systemic or systemic-like insecticides widely used in maize crops. Their heavy action in the nervous system of target insects also means a high toxicity to non-target pollinator insects such as honey bees which can get in touch with them through pollen and nectar during foraging activities. These insecticides have even been suspected to cause a significant decrease of honeybee colonies that has been observed in many countries since the past decade. Since September 1st 2008, the European Commission set new MRLs in food and feed of plant and animal origin. The pesticides included in this study have MRLs in honey and pollen between 10 and 50 ng g(-1). In the present work, an analytical method was developed with the aim of determining residues of fipronil and some of its metabolites (fipronil sulfone, fipronil sulfide, fipronil desulfinyl and fipronil carboxamide), thiamethoxam and imidacloprid in honey and pollen samples. The extraction optimization was performed using a Doehlert experimental design by studying two factors, the mixture and the ratio of solvents used. Prior to the extraction procedure, raw hive samples containing honey, pollen and wax were centrifuged at 4000 rpm. The upper solid material was removed, and 1 g of the lower phase was mixed with 3 mL of the optimized mixture of methanol/water (10/90). The extract was passed through a florisil cartridge and the target compounds were eluted with methanol and analysed by LC-MS/MS in selective reaction monitoring (SRM) mode. The method was validated according to the guidelines included in the SANCO/10684/2009 document and the ISO 11843 standard for the following parameters: decision limit (CCalpha), detection capability (CCbeta), recovery, repeatability and reproducibility at 0.5, 1 and 1.5 folds the MRLs. Ion suppression/enhancement effects into the ion source were also assessed. The CCbeta values were included between 0.83 and 4.83 ng g(-1), well below the current MRLs. The validated method was applied to the determination of the target pesticides in 91 samples collected in colonies from 73 apiaries of NW Spain (two sampling campaigns during 2008). None of the target insecticides were detected among all the collected samples.

Simultaneous extraction and cleanup method based on pressurized solvent extraction for multiresidue analysis of pesticides in complex feed samples.

The development of a multiresidue method based on pressurized solvent extraction (PSE) to determine a large number of pesticides (mostly pyrethroids and organochlorines) in cattle feed is described. As far as we know, this is the first work dedicated to the PSE of many of the target pesticides from animal feed. A mixed level fraction design was performed to investigate the influence of several operational variables on the PSE procedure; integrated cleanup strategies were also assessed allowing the direct chromatographic analysis of the extracts. Method accuracy was evaluated by the analysis of a certified reference material (BCR-115) and different fortified cattle feed samples. Most analytes were recovered in the range of 70-110%, with relative standard deviations generally lower than 15%. Limits of detection (LODs) were below the maximum residue levels (MRLs) set by the European Union for animal feed and main crops used in the preparation of feedingstuffs. The applicability of the proposed method was demonstrated by the analysis of real cattle feed samples collected from 23 dairy farms located in Galicia (NW Spain).

Dispersive solid-phase extraction followed by liquid chromatography-tandem mass spectrometry for the multi-residue analysis of pesticides in raw bovine milk.

A fast multi-residue method based on dispersive solid-phase extraction (DSPE) followed by liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of 44 pesticides in raw bovine milk. Raw bovine milk samples did not percolate through SPE cartridges usually applied for pesticide extraction from homogenized pasteurized milk samples. Therefore, a DSPE technique was implemented and validated for the first time in this work. Graphitized non-porous carbon and C18 modified silica materials were tested both in combination with magnesium sulfate and bonded silica with ethylenediamine-N-propyl phase. The efficiency of the DSPE process was studied at several concentration levels obtaining the higher recoveries with C18 material. The method performance was also assessed and the limits of quantification reached the ng g(-1) level, complying with the most recent maximum residue levels. The DSPE method was also shown to be suited to both the fatty and skimmed fractions issued from raw milk. Finally, the extraction method was successfully applied to the analysis of raw milk samples collected in 23 farms of dairy cattle from NW Spain (Galicia).

Simple approach for the determination of brominated flame retardants in environmental solid samples based on solvent extraction and solid-phase microextraction followed by gas chromatography-tandem mass spectrometry.

A viable approach for the analysis of polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) in sewage sludge samples is presented in this paper. The proposed method combines ultrasound-assisted extraction (UAE) of the solid sample and headspace solid-phase microextraction (HS-SPME) of the obtained extract, followed by gas chromatography coupled to tandem mass spectrometry (GC-MS-MS) analysis. Different parameters affecting the extraction process are evaluated and optimized. The addition of a small amount of Florisil to the sample during UAE provides a significant improvement of the chromatographic background and, at the same time, a much more efficient HS-SPME. Extensive method validation is performed using real sewage sludge samples. The proposed method exhibits good performance in terms of linearity and precision, with recoveries exceeding 92% and limits of detection in the sub ng g(-1) level. Practical applicability is demonstrated through the analysis of real contaminated sewage sludge and sediment samples in which some of the target PBDEs are detected and quantified. This proposed combined methodology represents a large time-saving when compared to other classic multi-step solvent extraction methods and it constitutes a suitable approach for the analysis of the target compounds in environmental complex solid samples.

Headspace solid-phase microextraction gas chromatography tandem mass spectrometry for the determination of brominated flame retardants in environmental solid samples.

A headspace solid-phase microextraction gas chromatography coupled with tandem mass spectrometry (HSSPME-GC-MS-MS) methodology for determination of brominated flame retardants in sediment and soil samples is presented. To the best of our knowledge, this is the first time that SPME has been applied to analyze polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) in environmental solid samples. Analyses were performed using 0.5-g solid samples moisturized with 2 mL water, employing a polydimethylsiloxane (PDMS) fiber coating, exposed to the headspace at 100 degrees C for 60 min. Several types of environmental solid samples were included in this study and the extraction efficiency was related to the organic matter content of the sample. Calibration was performed using real samples, and the method showed good linearity over a wide concentration range, precision, and afforded quantitative recoveries. The obtained detection limits were in the sub-ng g(-1) for all the target analytes in both samples. The proposed procedure was applied to several marine and river sediments and soils, some of which were found to contain PBDEs at concentrations in the ng g(-1) level; BDE-47, BDE-100, and BDE-99 were the major congeners detected. The proposed method constitutes a rapid and low-cost alternative for the analysis of the target brominated flame retardants in environmental solid samples, since the clean-up steps, fractionation, and preconcentration of extracts inherent to the classical multi-step solvent extraction procedures are avoided.