A REFERENCE METHOD FOR THE ANALYSIS OF ALDOSTERONE IN BLOOD BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION TANDEM MASS-SPECTROMETRY

A high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS/MS) reference metho d for the quantitation of aldosterone in serum and plasma has been dev eloped. Samples were extracted with dichloromethane/diethyl ether, con taining flumethasone as internal standard (IS). Chromatography was per formed on a phenyl column using 50 mM ammonium formate (pH 7.1)/methan ol (50/50, v/v) as mobile phase. Analysis was in negative-ionization m ode by selected reaction monitoring (aldosterone m/z 359.2 --> 331.2; IS m/z 455.0 --> 379.0). The assay was linear over the range 15-500 pg /mL, with limits of detection and quantitation of 10 and 15 pg/mL, res pectively. Imprecisions of the assay at 15, 20, 150, and 450 pg/mL wer e 18.5, 8.8, 10.6, and 9.5%, respectively. The accuracy of the method ranged from 93.1 to 98.9% with absolute recoveries between 84.0 and 91 .3% (aldosterone) and 88.0 and 92.3% (IS). We present a case study of a patient admitted, with suspected primary hyperaldosteronism, on the basis of a high radioimmunoassay (RIA) aldosterone concentration. The results suggest that RIA was unreliable, causing unnecessary patient d iscomfort and a costly g-day hospital stay. The specific HPLC-API-MS/M S assay described offers the sensitivity and accuracy required to asse ss abnormal aldosterone production in hypertensive patients. (C) 1997 Academic Press.