High-throughput screening of corticosteroids and basic drugs in horse urine by liquid chromatography-tandem mass spectrometry.

This paper describes two high-throughput liquid chromatography-tandem mass spectrometry (LC-MS-MS) methods for the screening of two important classes of drugs in equine sports, namely corticosteroids and basic drugs, at low ppb levels in horse urine. The method utilized a high efficiency reversed-phase LC column (3.3 cm L x 2.1 mm i.d. with 3 microm particles) to provide fast turnaround times. The overall turnaround time for the corticosteroid screen was 5 min and that for the basic drug screen was 8 min, inclusive of post-run and equilibration times. Method specificity was assessed by analysing a total of 35 negative post-race horse urine samples. No interference from the matrices at the expected retention times of the targeted masses was observed. Inter-day precision for the screening of 19 corticosteroids and 48 basic drugs were evaluated by replicate analyses (n = 10) of a spiked sample on 4 consecutive days. The results demonstrated that both methods have acceptable precision to be used on a routine basis. The performance of these two methods on real samples was demonstrated by their applications to drug administration and positive post-race urine samples.