Microwave-accelerated derivatization for the simultaneous gas chromatographic-mass spectrometric analysis of natural and synthetic estrogenic steroids

A rapid microwave-accelerated derivatization process for the GC-MS analysis of steroid estrogens, estrone (El), 17 beta-estradiol (E2), estriol (0), 17(x-ethynylestradiol (EE2) and mestranol (MeEE2), was developed. Under microwave irradiation, the five estrogenic hormones studied were simultaneously derivatized, with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + trimethylchlorosilane (TMCS) in pyridine solution. Effects of irradiation time (15-120 s) and power level (240-800 W) on the yield of the derivatization were investigated. The derivatization under the irradiation of 800 W microwave for 60 s produced comparable results when compared with the conventional heating process in a sand bath for 30 min at 80 degrees C in terms of derivatization yield, linearity and precision for all steroid hormones tested. The calibration curves are linear between 3.00 and 3.00 x 10(2) mu g mL(-1). The square of the regression coefficients (R-2) range from 0.979 to 1.000. The applicability of the method was evaluated on spiked river and distilled water samples at two concentrations, 25.0 and 2.00 x 102 ng mL(-1). The recoveries obtained by using microwave heating (60 s, 800 W) were similar to those by conventional heating. When combined solid-phase extraction (SPE) with the application of the microwave-accelerated derivatization proposed here, the detection limits of 0.02-0.1 ng L-1 for the steroid hormones have been achieved. The results demonstrated that microwave-accelerated derivatization is an efficient and suitable sample preparation method for the GC-MS analysis of estrogenic steroids. (C) 2007 Elsevier B.V. All rights reserved.