Investigation of internal standard substances for the determination of beta-estradiol in environmental samples

Three deuterated beta-estradiol compounds (2,4-d(2), 16,16,17-d(3), 2,4,16, 16-d(4)) were investigated for use as internal standard substances in the d etermination of beta-estradiol. The mass spectrum of two of the deuterated compounds (2,4-d(2), 2,4,16,16-d(4)) showed structural changes due to hydro lysis (1 M-HCl/methanol, 80 degrees C, 20 min), which was required for the decomposition of conjugates in the sample pretreatment. On the other hand, the mass spectrum of the 16,16,17-deuterated compound was not changed. Ther efore, we advise that beta-estradiol-16,16,17-d(3) should be used as the in ternal standard. In case where beta-estradiol-2,4,16,16-d(4) must be used, it should be spiked after hydrolysis.