Determination of organic pollutions in natural water by LC-MS/MS

Organic pollution of waters by human and animal wastes is a longstanding problem and has serious impacts to water quality and to aquatic life. Coprostanol has been used for several decades to identify pollution of waters by sewage. Bile acids and fecal sterols are now considered to be indicators of pollution by agricultural animal production. I have developed a high performance liquid chromatography - atmospheric pressure chemical ionization mass spectrometry (LC-MS/MS) method for simultaneous determination of sterols and bile acids. I compared reversed phase chromatography of the compounds with two chromatographic columns, the ZORBAX Eclipse XDB-C8 and Restek Ultra II C18 columns. The ZORBAX Eclipse XDB-C8 column allows separation of the compounds within 38 min, while separation with the Restek Ultra II C18 requires more than 120 min. I optimized the mobile phase for the separation. The final method uses the ZORBAX Eclipse XDB- column with a gradient of acetonitrile:MeOH/ 0.2 mM ammonium acetate in water at a flow rate of 0.5/min and a column maintained at ambient temperature. The developed method shows a good linearity and high repeatability. The method was applied for the determination of selected bile acids and sterols in wastewater treatment plant (WWTP) influent and effluent, and stream water samples suspected to be impacted by the WWTP effluent, septic system leachate, and cattle pasture runoff.