Determination of avermectins: a QuEChERS approach to the analysis of food samples.

We present a simple method for extracting avermectines from meat, based on a QuEChERS approach followed by liquid chromatography (LC) coupled to triple quadrupole (QqQ) tandem mass spectrometry (MS/MS). The compounds considered are ivermectin, abamectin, emamectin, eprinomectin, doramectin and moxidectin. The new method has been fully validated according to the requirements of European Decision 657/2002/CE (EU, 2002). The method is suitable for the analysis of avermectins at concentration as low as 2.5 µg kg(-1), and allows high sample throughput. In addition, the detection of avermectins by high resolution mass spectrometry using a quadrupole-Orbritrap (Q-Orbitrap) hybrid instrument has been explored, and the target Selected Ion Monitoring data dependent MS/MS (t-SIM-dd MS/MS) mode has been found to provide excellent performance for residue determination of target analytes.

New method for the analysis of lipophilic marine biotoxins in fresh and canned bivalves by liquid chromatography coupled to high resolution mass spectrometry: a quick, easy, cheap, efficient, rugged, safe approach.

A new method for the analysis of lipophilic marine biotoxins (okadaic acid, dinophysistoxins, azaspiracids, pectenotoxins, yessotoxins, spirolids) in fresh and canned bivalves has been developed. A QuEChERS methodology is applied; i.e. the analytes are extracted with acetonitrile and clean-up of the extracts is performed by dispersive solid phase extraction with C18. The extracts are analyzed by ultra-high performance liquid chromatography coupled to a hybrid quadrupole-Orbitrap mass spectrometer, operating in tandem mass spectrometry mode, with resolution set at 70,000 (m/z 200, FWHM). Separation of the analytes, which takes about 10min, is carried out in gradient elution mode with a BEH C18 column and mobile phases based on 6.7mM ammonia aqueous solution and acetonitrile mixtures. For each analyte the molecular ion and 1 or 2 product ions are acquired, with a mass accuracy better than 5ppm. The quantification is performed using surrogate matrix matched standards, with eprinomectin as internal standard. The high-throughput method, which has been successfully validated, fulfills the requirements of European Union legislation, and has been implemented as a routine method in a public health laboratory.

High-throughput method for the determination of nitroimidazoles in muscle samples by liquid chromatography coupled to mass spectrometry.

We present a high-throughput confirmatory method for the analysis of 11 nitroimidazoles in muscle samples (metronidazole, MNZ; dimetridazole, DMZ; ronidazole, RNZ; tinidazole, TNZ; carnidazole, CRZ; secnidazole semihydrate, SCZ; ornidazole, ORZ; metronidazole-hydroxy, MNZ-OH; ipronidazole, IPZ; ipronidazole-hydroxy, IPZ-OH; and dimetridazole-hydroxy, HMMNI). Extraction with acetonitrile is efficient and simple, with the majority of recoveries ranging between 65 and 101%, and without the need for clean-up of the extracts. The chromatographic analysis is performed using UPLC-QqQ-MS in the MRM mode, with an electrospray source operated in positive mode. Total chromatographic analysis time is 12 min. This method has been fully validated in muscle according to Decision 657/2002/CE guidelines, and the CCα values obtained were in the range of 0.04-0.4 µg·kg(-1). The method is currently used for the analysis of muscle samples and has been tested in other matrices of animal origin, such as kidney, retina and egg, with excellent results.

Use of gel permeation chromatography for clean-up in the analysis of coccidiostats in eggs by liquid chromatography-tandem mass spectrometry.

An analytical method for determination and confirmation of nine coccidiostatics in eggs is reported. Ethyl acetate is used as extraction solvent, with satisfactory results, and simple automated clean-up is based on gel-permeation chromatography (GPC) . The target compounds are then analysed by liquid chromatography-electrospray ionization-tandem mass spectrometry. The method was validated in-house in accordance with Commission Decision 2002/657/EC. Trueness and precision were determined at four concentrations, and the mean errors obtained were <10 %, with relative standard deviations ranging from 3 to 18 %. For three non-authorized coccidiostatics (clopidol, ethopabate, and ronizadole), decision limit and detection capability were in the ranges 0.12-0.16 and 0.18-0.23 µg kg(-1), respectively. The results obtained prove the suitability of this new analytical method for routine monitoring of these substances in eggs.

Development and validation of a multiclass method for the analysis of antibiotic residues in eggs by liquid chromatography-tandem mass spectrometry.

A multiclass method for the analysis of residues, in egg matrices, of 41 antimicrobial agents belonging to seven families (sulfonamides, diaminopyridine derivates, quinolones, tetracyclines, macrolides, penicillins and lincosamides) was developed and validated according to the requirements of European Commission Decision 2002/657. Compounds were extracted with a pressurized liquid extraction (PLE) technique using a 1:1 mixture of acetonitrile and a succinic acid buffer (pH 6.0) at 70 °C. As this resulted in clear extracts, no further clean-up was necessary. Analytes were determined by ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPL-MS/MS) in a chromatographic run of 13 min. Calibration was carried out with spiked blank samples subjected to the entire analytical procedure. Five compounds, two of them isotopically labelled, were used as internal standards. Most analytes were quantified with errors below 10%. Precision in terms of reproducibility standard deviation was between 10% and 20% in most cases. CCα values were in the range 0.5-3.8 µg kg⁻¹ for the non-authorized compounds. The proposed method would enable an experienced analyst to process about 25 samples per day.

High-throughput multiclass method for antibiotic residue analysis by liquid chromatography-tandem mass spectrometry.

A simple and rapid method has been developed for the residue analysis of 39 antibiotics (tetracyclines, quinolones, penicillins, sulfonamides and macrolides) in foodstuffs of animal origin. The method combines an effective extraction technique, which uses water-methanol as extracting solvent, with ultra-high-pressure liquid chromatography-tandem mass spectrometry, allowing both confirmation and quantification in a single chromatographic run. The multiresidue method has been validated in chicken muscle matrix according to European Union Decision 2002/657/EC. It has been implemented as a routine method in a Public Health Laboratory, instead of the five plates test and LC methods previously used.

Analysis of thyreostatic drugs in thyroid samples by liquid chromatography tandem mass spectrometry: comparison of two sample treatment strategies.

A method based on ultra-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (UPLC-MS/MS) for the determination of six thyreostatic drugs in thyroid tissue has been optimised and validated in accordance with Decision 2002/657/EC. Sample extraction was evaluated in methanol and in ethyl acetate, the latter which gave better results. Two clean-up strategies were compared: one based on silica cartridges (SPE), and the other, on gel permeation chromatography (GPC). Recoveries ranged from 40% to 79% for the SPE approach and from 80% to 109% for GPC. Quantification was performed with blank tissue samples spiked with the analytes in the range 50-500microgkg(-1). 5,6-Dimethyl-2-thiouracil and 2-mercaptobenzimidazole-d(4) were used as internal standards. Decision limit (CCalpha) and detection capability (CCbeta) ranged from 1 to 15microgkg(-1) and from 6 to 25microgkg(-1), respectively. The accuracy of the method was calculated as percent error, which was less than 10%. The relative standard deviation in reproducibility conditions ranged between 2% and 14%.

Analysis of thyreostatic drugs in thyroid samples by ultra-performance liquid chromatography tandem mass spectrometry detection.

A method based on ultra-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry for the determination of six thyreostatic drugs in thyroid tissue has been optimised and validated in accordance with the Decision 2002/657/EC. Samples are extracted with methanol and the extracts cleaned-up on silica cartridges. The recoveries range from 40% for 6-phenyl-2-thiouracil to 79% for 2-thiouracil. Quantification is carried out with blank tissue samples spiked with the analytes in the range 25-500 microg kg(-1). 5,6-Dimethyl-2-thiouracil is used as internal standard. CCalpha and CCbeta are in the ranges 4.3-16.1 microg kg(-1) and 8.7-20.7 microg kg(-1), respectively. Accuracy, expressed as percentage of error, is lower than 6% and relative standard deviation in reproducibility conditions falls between 5.6 and 10.3%. Nowadays, the proposed method is routinely implemented in the laboratory of the Agència de Salut Pública de Barcelona and allows processing of up to 20 samples per day.

Validation of a method for the analysis of quinolones residues in bovine muscle by liquid chromatography with electrospray ionisation tandem mass spectrometry detection.

A liquid chromatography-tandem mass spectrometry method for the determination and confirmation of nine quinolones was optimised and validated according to Commission Decision 2002/657/EC. Analytes were extracted from veal muscle with water and extracts purified with 96-well plates Oasis HLB cartridges. Separation was carried out in a silica-based C(18) column (50mmx2.1mm) with mobile phases consisting of water/acetonitrile mixtures containing acetic acid. Linear calibration curves in the ranges 4-400 and 50-800ngg(-1), with correlation coefficients at least 0.995, were obtained for all the analytes. At concentration levels above 10ngg(-1), quantification errors were lower than 10% and repeatability and within-laboratory reproducibility standard deviations below 6% and 10%, respectively. Decision limits and detection capabilities are reported.

Effect of brine discharge from a desalination plant on macrobenthic communities in the NW Mediterranean.

This paper examines the possible effects of discharges from a desalination plant on the macrobenthic community inhabiting the sandy substratum off the coast of Blanes in Spain (NW Mediterranean) using multivariate and univariate analyses. Two controls and one putatively impacted location were selected and visual censuses were carried out 12 times before and 12 times after the plant had begun operating. No significant variations attributable to the brine discharges from the desalination plant were found. The failure to record any impact may be explained by the high natural variability that is a characteristic feature of bottoms of this type and also by the rapid dilution undergone by the hypersaline brine upon leaving the discharge pipe.