Direct analysis in real time high‐resolution mass spectrometry for high‐throughput analysis of antiparasitic veterinary drugs in feed and food

RATIONALE: Direct analysis in real time (DART) is a novel ionization technique that has been demonstrated in numerous applications as a useful tool for fast and convenient mass spectrometry (MS)-based analysis of complex samples. In this study, the feasibility of DART ionization coupled to a high-resolution mass spectrometer utilizing an orbitrap mass analyzer (orbitrap MS) for high-throughput analysis of antiparasitic veterinary drugs was explored. METHODS: To obtain the best DART-orbitrap MS performance, stepwise optimization of instrumental parameter settings, such as ionization gas temperature and mass resolving power, was performed. The optimized method was applied to feed and bovine milk samples previously extracted following a QuEChERS-like strategy. RESULTS: Most antiparasitic drugs could be analyzed following the described method. Positive DART ionization provided the protonated molecules [M+H](+); in negative DART ion mode, deprotonated molecules [M-H](-) were observed. As an exception, polyether ionophores could be observed as the sodiated adducts [M+Na](+). Samples of milk and feed were extracted using a modified QuEChERS method for the determination of benzimidazoles and coccidiostats respectively and quantification was carried out by matrix-matched calibration curves. CONCLUSIONS: The combination of an analysis time of less than 1 min per sample and the possibility to acquire accurate masses under high mass resolving power (HR) makes the DART-HRMS technique an effective tool for rapid qualitative screening of antiparasitic veterinary drugs. Additionally, the results obtained in this study demonstrated the feasibility of this approach to quantify target analytes at levels down to 1 µg kg(-1) for benzimidazolic compounds in milk and 0.25 mg kg(-1) for coccidiostats in chicken feed.