A new analytical method for the determination of beta-blockers and one metabolite in the influents and effluents of three urban wastewater treatment plants

Abstract

Pharmaceutical are emerging contaminants in waste waters from where they are discharged into surface water were, they may be harmful to aquatic organisms. Beta-blockers are consumed in high tonnage a year because of the cardiovascular disease of the population, being incompletely metabolized. They are removed from the body as parent drug or as metabolite in wastewater. A sensitive method using off-line solid-phase extraction (SPE) and liquid chromatography coupled with mass spectrometry (LC-MS/MS) has been developed for determination of 6 beta-blockers (bisoprolol, nadolol, betaxolol, atenolol, propranolol, pindolol) and one metabolite (4-hydroxipropranolol) in the influents and effluents of three urban waste water treatment plants (WWTPs). Extraction of the compounds was performed on Oasis C18 cartridges at pH 10 adjusted with ammonium hydroxide. As LC mobile phase formic acid 0.1 % in water and methanol in gradient elution was used to separate the analytes in 13 minutes on Luna C18 column kept at 45 0C. A linear response was obtained for all substances in the range of 1-100 ng/mL with determination coefficients > 0.99. The parameters of SPE procedure and of LC-MS method were optimized to obtain the best results. Method was validated and beta-blocker recoveries after SPE in wastewater were in the range of 71.2-103.3% with satisfactory intra-day and inter-day precision (RSD%) being situated between 4.7-8.4% and 8.1-14.4 %, respectively. Optimization of LC-MS parameters generated low LOQ values between 0.34 and 7.37 ng/mL. Atenolol was detected in all samples at higher average concentrations which ranged between 94.6 ng/L and 208.6ng/L (effluent samples, influent). The other 3 beta-blockers: bisoprolol, betaxolol and propranolol were detected in influents in mean concentrations of 100.1ng/L, 44.9ng/L and 26.8 ng/L and in effluents in mean concentrations of 51ng/L, 16.9ng/L and 19.4ng/L. Propranolol was eliminated with the lowest average yields ranging from 25.19% to 31.78%, whereas atenolol, bisoprolol and betaxolol were eliminated from WWTP with average yields ranging from 44.97-60.96%, 46.8-52.9% and 47.05- 69.08%, respectively. Results obtained suggest that adopted wastewater treatment processes are not efficient to remove these compounds and by penetrating into surface waters through evacuated effluents can adversely affect aquatic organisms.