Determination of steroid estrogens in wastewater by immunoaffinity extraction coupled with HPLC-electrospray-MS

A new method, based on immunoaffinity extraction coupled with liquid chromatography/electrospray mass spectrometry (LC/ESI-MS) is described for the determination of the steroid estrogens beta-estradiol (E2), estrone (E1), and alpha-ethynylestradiol (E2) in wastewater. The use of highly selective immunosorbents in sample preparation prior to analysis allows the removal of interfering sample matrix compounds present in the wastewater extracts that would otherwise cause severe ionization suppression of the estrogens during the electrospray process. In addition, immunoextraction removes much of the isobaric noise from the selected ion monitoring chromatograms, increasing the signal-to-noise ratios for analytes, and contributing to the low detection limits (0.18 and 0.07 ng/L for E2 and E1, respectively) achieved by the current method. The method was applied to analysis of estrogens in two wastewater effluents. Recoveries of E2 and E1 were excellent (>90%), while the nonimmunogen (but structurally related) analyte EE2 was not retained (recovery <2%) from effluent extracts by the immunosorbent. This illustrates the extreme selectivity of the immunoextraction purification step. Precision of the method was high, with relative standard deviations below 5%. Concentrations of E2 in wastewater varied from 0.77 to 6.4 ng/L, while concentrations of E1 were greater (1.6-18 ng/L).