Determination of Oestradiol-17ß in Human Serum by Isotope Dilution-Mass Spectrometry Definitive Methods in Clinical Chemistry, II

Summary: A definitive method is described for the measurement of oestradiol-17ß in human serum. The method is based on the principle of isotope dilution-mass spectrometry. The analytical procedure consists of the following Steps: (1) addition of [4-14C]oestradiol-17ß to the plasma sample; (2) extraction of the 14C-labelled and the non-labelled oestradiol-17ß with dichloromethane; (3) purification of the oestradiol-17ß fraction by column chromatography on Sephadex LH-20; (4) formation of the 3,17ß-diheptafluorobutyric ester of oestradiol-17ß; (5) selected ion monitoring at m/z-values 664 and 666 by gas liquid chromatography-mass spectrometry. The accuracy of the method is based on the high specificity of mass spectrometry and on the exact control of recovery employing the principle of isotope dilution. Coefficients of Variation from day to day varied between 1.0 % and 2.5 % in the ränge of 0.319 to 3.53 nmol/1. The lower limit of detection (ratio of signal to noise 3:1) is 5 pg oestradiol-17ß per sample. Bestimmung von östradiol-17ß im menschlichen Serum mit Hilfe der massenspektrometrischen Isotopen