DETERMINATION OF XR510, A BALANCED ANGIOTENSIN-II RECEPTOR ANTAGONIST, IN DOG AND RAT PLASMA BY COMBINED LIQUID-LIQUID SOLID-PHASE EXTRACTION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A sensitive and selective high-performance liquid chromatographic meth od for the determination of XR510 (I), a new non-peptide angiotensin I I (AII) receptor antagonist with balanced affinity for AT, and AT, rec eptor subtypes is described. I and the internal standard, XR513, were extracted from acidified plasma by combined liquid - liquid/solid-phas e extraction and chromatographed on a phenyl column with ultraviolet a bsorbance detection at a wavelength of 272 nm. The mobile phase consis ted of a mixture of acetonitrile and sodium phosphate buffer. For both rat and dog plasma, the limit of quantitation was 5 ng/ml. This metho d has been validated and successfully utilized to investigate the disp osition of I.