Development and validation of an improved HPLC-UV method for the determination of tildipirosin in horse plasma

A simple, rapid, low-cost, and sensitive high-performance liquid chromatographic method was developed to determine tildipirosin in horse plasma. Plasma samples were extracted with diethyl ether, and after evaporation, tildipirosin was determined by reverse-phase chromatography with an ultraviolet detector set at a wavelength of 289 nm. Tildipirosin was separated on a Zorbax Eclipse XDB-C18 column, 150 x 3.0 mm, 5 μm with gradient chromatographic elution. The retention times were 3.0 min and 6.4 min for tildipirosin and tylosin tartrate, respectively. The total run time was 9 minutes in this method. Calibration curves ranged from 0.1 to 3 μg/mL. The lower limit of detection for plasma was 0.035 μg/mL, and the lower limit of quantitation was 0.1 μg/mL. Both accuracy and precision were always < 12% except for LLOQ < 20%. Mean recovery was 99.5 %. This procedure can be applied to determine tildipirosin concentrations in plasma and be useful to perform pharmacokinetic studies.