Determination of serum unconjugated estrone, estradiol-17 beta and estriol during pregnancy by selected ion monitoring.

A simple, rapid and highly specific method by selected ion monitoring (SIM), using 9 alpha, 11 alpha-[2H2]estrone, [2,4-2H2]estradiol-17 beta and 2,4-[2H2]estriol as internal standards, was developed for the determination of serum estrogens during pregnancy. Serum samples were submitted to a simple extraction procedure and were analysed after formation of the trifluoroacetic anhydride derivative. The inter-assay coefficients of variation for estrone, estradiol-17 beta and estriol were 3.73%, 3.42% and 3.49%, respectively. The results obtained by SIM were compared with analysis performed using radioimmunoassay.