Quantitative detection of salmeterol after inhalation in equine urine by liquid chromatography/tandem mass spectrometry

Abstract
A sensitive, accurate and precise liquid chromatography/tandem mass spectrometry (LC/MS2) method was developed for the quantification of salmeterol in the urine of horses. The method consists of a liquid-liquid extraction with tert-butylmethyl ether and isopropanol at pH 12 after enzymatic hydrolysis. The extracts are analysed using an LC/MS system equipped with an electrospray ionisation (ESI) probe. Method validation showed excellent linearity, specificity, accuracy, precision and intra-laboratory repeatability and reproducibility. The limit of quantitative detection was 0.25 ng/mL and the limit of detection was 0.125 ng/mL. The excretion profile was determined after administration of 500 µg salmeterol (Serevent®) to four standard-bred mares via a metered dose inhaler (MDI) with an Equinehaler® adapter. Salmeterol was detected from 1 h until 12 h post-administration. Maximum urinary concentrations varied between 2.3 and 14.9 ng/mL. Copyright © 2002 John Wiley & Sons, Ltd.

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