3 hormone replacement therapy. Ethinylestradiol, a synthetic estrogen and the most potent, is a main component of many birth control pills. It was hypothesized that these combined sources of estrogens would likely result in levels that were in the parts-perbillion, or μg/L, range. There have been a few standard methods of detecting estrogens in water, but the most common is solid phase extraction (SPE) followed by either gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). A standard F-test was performed to compare GC (σ = 9-15%, n = 6)2 and LC (σ = <4%, n = 4)4. The test showed that LC does not have a significant improvement in precision over GC. However, GC is limited by factors including high molecular weights and nonvolatility. Procedures using GC/MS also require derivatization of the estrogens before measurements can be taken. Liquid chromatography does not require derivatization, which saves on both time and materials. Solid-phase extraction is usually employed instead of liquid-liquid extraction for several reasons, including the ability to do on-line coupling with chromatography and a higher degree of selectivity8. Therefore, SPE followed by LC/MS was the method used in this study.
Experimental Procedure Collection The samples were collected in 1 liter amber glass bottles from tap water in homes in the areas of the Salt Lake Valley mentioned in the introduction. In order to prevent degradation and clean up any residual chlorine, 50 mg/L of ascorbic acid and 200 mg/L of sodium azide were added to the samples. They were then kept at 4°C and in the dark until filtering and extraction were begun. Wastewater was also collected in amber glass bottles, treated with ascorbic acid and sodium azide and filtered with 0.45 µm Whatman filter paper prior to experimentation. All sample volumes were measured before proceeding. One hundred ng (10 µL of a 10 mg/L methanolic stock solution) of the surrogate standard, estrone-d4, was then added to each filtrate to account for any loss of estrogens throughout the procedure. (8) Ramsey, E. D.; Minty, B.; Rees, A. T. Anal. Commun. 1997, 34, 261-264.