Determination of 5-n-Butyl-4-{4-[2-(1H-tetrazole-5-yl)1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichloridephenyl)-3H-1,2,4-triazol-3-one,a new Angiotensin type 1 receptor antagonist in rat plasma by LC-ESI-MS: Application to pharmacokinetic studies

A simple and sensitive reversed-phase LC-ESI-MS method to identify and quantitate 5-n-butyl-4-{4-[2-(1H-tetrazole-5-yl)- 1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichloridephenyl)-3H-1,2,4-triazol-3-one (1b), a new Angiotensin 11 type 1 receptor antagonist in rat plasma has been developed and validated. Sample preparation used a simple liquid-liquid extraction with ethyl acetate. Separation was achieved by gradient elution on a C-18 column. The mobile phase consisted of acetonitrile and water (0.05% triethylamine and 0.05% acetic acid) at a flow rate of 0.2 mL min(-1). The detection utilized selected ion monitoring (SIM) in the negative mode at m/z 507.1 and m/z 407.2 for the deprotonated molecular ions of 1b and the internal standard irbesortan, respectively. The lower limit of quantification was reproducible of 5 ng mL(-1) with 100 mu L of plasma and the good linear was observed in the 5-500 ng mL-1 range. This concentration range corresponded well with the plasma concentrations of 1b in pharmacokinetic studies. Recoveries of 1b in rat plasma were 76.1, 74.6 and 79.0% at 5, 50 and 500 ng mL-1. The RSD of intra-assay and inter-assay variations were all less than 5%. This validated LC-ESI-MS assay is an economic, quick, precise and reliable method for the analysis of 1b in pharmacokinetic studies.