Direct analysis of valsartan or candesartan in human plasma and urines by on-line solid phase extraction coupled to electrospray tandem mass spectrometry.

AT1 receptor blockers are agents for the treatment of hypertension. Rapid and precise assay methods are needed to evaluate possible sub- or overdosage. A direct on-line solid phase extraction coupled to tandem mass spectrometry was developed and validated to determine valsartan (5-2000ng/mL) or candesartan (1-200ng/mL) in human plasma and urines. Both intra- and inter-assay accuracy and precision were in the range 89.2-111% and 0.9-16.9% RSD. Total run time was 4.5min. This on-line clean-up-MS method was found to be robust for the analysis of a high number of samples with unvarying performance.