No abstract

A fast and straightforward generic procedure for the simultaneous extraction of various classes of pesticides, mycotoxins, plant toxins, and veterinary drugs in various matrixes has been developed, for subsequent analysis by liquid chromatography with mass spectrometric detection. As a first step, four existing multianalyte procedures and three newly proposed methods were compared for a test set of 172 pesticides, mycotoxins, and plant toxins spiked to a feed matrix. The new procedures, which basically involved extraction/dilution of the sample with water and an acidified organic solvent (methanol, acetonitrile, or acetone), were most promising. The three new generic extraction methods were further tested for applicability to other matrixes (maize, honey, milk, egg, meat). Overall, the best recoveries were obtained for acetone, followed by acetonitrile. With respect to matrix effects, acetonitrile was the most favorable solvent and methanol was the worst. The occurrence of matrix effects decreased for the matrixes in the order of feed > maize > meat > milk > egg > honey. The extraction method selected as the default procedure (water/acetonitrile/1% formic acid) was also evaluated for applicability to multiple classes of veterinary drugs in all six matrixes, with satisfactory results. Finally, the generic extraction procedure was validated for 136 pesticides, 36 natural toxins, and 86 veterinary drugs in compound feed and honey at three levels (0.01, 0.02, and 0.05 mg/kg) using ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for analysis of the extracts. For over 80% of the analytes, recoveries were between 70 and 120% and precision (expressed as relative standard deviation) was mostly in the range of 5-10% (except for feed at 0.01 mg/kg; adequate recoveries for 62% of the analytes). The limits of detection were from <0.01 to 0.05 mg/kg for most analytes, which is usually sufficient to verify compliance of products with legal tolerances. The results clearly demonstrate the feasibility of the generic approach proposed. Application of the method in routine monitoring programs would imply a drastic reduction of both effort and time.

Ultra-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLC-ToF-MS) has been used for screening and quantification of more than 100 veterinary drugs in milk. The veterinary drugs represent different classes including benzimidazoles, macrolides, penicillins, quinolones, sulphonamides, pyrimidines, tetracylines, nitroimidazoles, tranquillizers, ionophores, amphenicols and non-steroidal anti-inflammatory agents (NSAIDs). After protein precipitation, centrifugation and solid-phase extraction (SPE), the extracts were analysed by UPLC-ToF-MS. From the acquired full scan data the drug-specific ions were extracted for construction of the chromatograms and evaluation of the results. The analytical method was validated according to the EU guidelines (2002/657/EC) for a quantitative screening method. At the concentration level of interest (MRL level) the results for repeatability (%RSD<20% for 86% of the compounds), reproducibility (%RSD<40% for 96% of the compounds) and the accuracy (80-120% for 88% of the compounds) were satisfactory. Evaluation of the CCβ values and the linearity results demonstrates that the developed method shows adequate sensitivity and linearity to provide quantitative results. Furthermore, the method is accurate enough to differentiate between suspected and negative samples or drug concentrations below or above the MRL. A set of 100 samples of raw milk were screened for residues. No suspected (positive) results were obtained except for the included blind reference sample containing sulphamethazine (88 μg/l) that tested positive for this compound. UPLC-ToF-MS combines high resolution for both LC and MS with high mass accuracy which is very powerful for the multi-compound analysis of veterinary drugs. The technique seems to be powerful enough for the analysis of not only veterinary drugs but also organic contaminants like pesticides, mycotoxins and plant toxins in one single method.

The use of beta-agonists as growth promoters in cattle breeding is forbidden in many countries for reasons of fair trade and consumer protection. In recent years the use of liquid chromatography (LC) tandem mass spectrometry (MS/MS) has been shown to be the method of choice for the control of beta-agonists. In this study an LC-MS/MS multiresidue analysis method is presented for trace analysis of 22 beta-agonists. A truly generic concept has been designed based on mixed-mode solid-phase extraction and positive electrospray ionisation LC-MS/MS operated in the multiple reaction monitoring mode. This method allows application to a wide variety of sample matrices such as urine, feed and hair, following minor modifications to the analysis procedure only. The method features fit-for-purpose sensitivity in urine as shown by CCalpha and CCbeta values of less than 0.2 and less than 0.5 microg/l respectively, for all beta-agonists studied (terbutaline and reproterol, less than 0.3 and less than 1.0 respectively). Similar but semiquantitative application to feed and hair showed CCbeta values of less than 10.0 and less than 5.0 microg/kg, respectively. A further simplification and improvement is demonstrated using Ultra Performance LC (UPLC) and fast-switching MS/MS. The successful validation of this method following the latest EU requirements and its application to real samples demonstrate that a new versatile tool has been achieved for veterinary control of beta-agonists.