Comprehensive screening and quantification of veterinary drugs in milk using UPLC–ToF-MS

Abstract

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 challenges of developing a generic extraction procedure to analyze multi‐class veterinary drug residues in milk and honey using ultra‐high pressure liquid chromatography quadrupole time‐of‐flight mass spectrometry

“…However, in the last few years, there have been an increased number of publications on multi-class methods for analysis of veterinary drugs in food using either LC-MS/MS or LC-TOF instruments. The extraction techniques that have been reported included a molecular weight cut-off filter (3 kD) for milk (150 veterinary drugs), [8] liquid-liquid extraction (LLE) for honey (42 antibiotics), [9] solid-phase extraction (SPE) using StrataX for egg, milk, animal tissues (100 veterinary drugs), [10,11] and QuEChERS for animal tissues (41 veterinary drugs), [12] and milk (21 veterinary drugs) [13] for different classes of veterinary drugs at various concentrations.…”

Comparative study of the LC–MS/MS and UPLC–MS/MS for the multi-residue analysis of quinolones, penicillins and cephalosporins in cow milk, and validation according to the regulation 2002/657/EC

“…Although it is also possible to find multi-class published methods [8,[16][17][18][19][20][21][22][23][24], some are not quantitative or do not determine the quality parameters necessary for validating the method according to European legislation [25]. Quinolones and penicillins regulated except AMOX and PENG, have been previously analysed in milk by ultra-high-performance liquid chromatography-time of flight-mass spectrometry (UPLC-TOF-MS) [19], while other authors [8] simultaneously measured the complete series of quinolones, penicillins and cephalosporins regulated by the EU in raw milk samples using UPLC with TOF to screen 150 veterinary drugs.…”

Application of EU guidelines for the validation of screening methods for veterinary drugs

“…[11,12] In this example, the focus is on the validation of tetracycline, oxytetracyline, and sulfamethoxazole in meat and eggs. Table 1 shows the MRLs for the registered drugs for meat and eggs.…”