The challenge of analyzing beta-blocker drugs in sludge and wastewater

In this study, different approaches were used to assess and overcome the severe effects of interference from the sample matrix from different types of sludges and wastewater on the analysis of nine beta-blockers and the beta sympathomimetic clenbuterol. The partitioning of the target compounds into sludge was investigated in wastewater treatment plants (WWTPs) in both Canada and Germany to evaluate whether this is an important mechanism for removal from sewage. Due to ion suppression in the electro spray interface, absolute recoveries were for certain compounds even lower than 20%. By using surrogate standards, acceptable relative recoveries of >75% were achieved for WWTP influents and effluents and for sludges. These matrix effects underline the need to use appropriate surrogate standards to aid in analyte quantitation. Using the developed methods, beta-blockers were detected at concentrations up to 2 microg/L in WWTP effluents, with metoprolol, sotalol, and atenolol present as the dominant compounds. Removal rates within WWTPs were highly inconsistent and ranged from 1-69%. Propranolol showed the greatest degree of partitioning into sludge with solid/water partition coefficients of one order of magnitude higher than those for all other compounds. However, even for propranolol, sorption did not contribute significantly to the overall elimination in WWTPs. It is likely that the removal of beta-blockers during waste water treatment can be attributed primarily to microbial biodegradation.