Determination of a beta(3)-agonist in human plasma by LC/MS/MS with semi-automated 48-well diatomaceous earth plate

Methods for the determination of beta (3)-agonist (A) in human plasma were developed and compared based on high-performance liquid chromatography (HPL C) with tandem mass spectrometric (MS/MS) detection using a turbo ion spray (TIS) interface. Drug and internal standard were isolated from plasma by t hree sample preparation methods, liquid-liquid extraction, Chem Elut cartri dges and 48-well diatomaceous earth plates, that successively improved samp le throughput for LC/MS/MS. MS/MS detection was performed on a PE Sciex API 365 tandem mass spectrometer operated in positive ion mode and using multi ple reaction monitoring (MRM). The precursor/product ion combinations of m/ z 625/607 and 653/515 were used to quantify A and internal standard, respec tively, after chromatographic separation of the analytes. Using liquid-liqu id extraction and Chem Elut cartridges, the assay concentration range was 0 .5-100 ng/ml. Using diatomaceous earth plates, the concentration range of t he assay was extended to 0.5-200 ng/ml. For all three assays, the statistic s for precision and accuracy is comparable. The assay accuracy ranged from 91-107% and intraday precision as measured by the coefficient of variation (CV) ranged 2-10%. The sample throughput was tripled when the diatomaceous earth plate method was compared with the original liquid-liquid extraction method. (C) 2001 Elsevier Science B.V. All rights reserved.