Simultaneous determination of omeprazole and domperidone in dog plasma by LC-MS method.

A liquid chromatography coupled with mass spectrometry method was developed and validated to determine omeprazole and domperidone simultaneously in dog plasma. Chromatographic separation was performed on a Narrow Bore C(18) column using methanol-10 mM ammonium acetate (68:32, v/v) as the mobile phase at the flow rate of 0.2 mL/min. The chromatographic separation was achieved in less than 7 min. Diazepam was used as the internal standard. Quantitative analysis was achieved by mass spectrometry detection using a mass spectrometer equipped with an electrospray ionization interface and operated in selected ion monitoring and positive ion mode using target ions at m/z 346 for omeprazole, m/z 426 for domperidone, and m/z 285 for internal standard, respectively. The lower limit of quantification was 1 ng/mL and a linear range of 1-200 ng/mL. The intra- and inter-day relative standard deviation was both less than 10%, and the accuracy values were higher than 90%. The method is sensitive and repeatable enough to be used in pharmacokinetic and bioavailability studies.