Analysis of neutral and basic pharmaceuticals in sewage treatment plants and in recipient rivers using solid phase extraction and liquid chromatography–tandem mass spectrometry detection

Analytical method was developed which allowed for the detection of four beta blockers (acebutolol, atenolol, metoprolol and sotalol), an antiepileptic drug (carbamazepine) and three fluoroquinolone antibiotics (ciprofloxacin, ofloxacin and norfloxacin) with a single pre-treatment and chromatographic method. The method included an isolation and concentration procedure using solid phase extraction, a separation step using high performance liquid chromatography and a detection procedure applying triple quadrupole mass spectrometry, which was working in the multiple reaction monitoring mode. The method was validated for ground, surface and sewage influent and effluent waters. Due to ion suppression in the electrospray source, the signals monitored for the analytes were less intense in sewage waters compared to ground and surface waters. The limits of quantification were as low as 1 ng L−1 in ground water and 3.5 ng L−1 in sewage influent. The method was successfully applied to the determination of the target compounds in raw and treated sewages of three treatment plants in Finland and in their recipient rivers. The results showed that many of the studied compounds pose a moderate to high persistency in sewage treatment as well as in the recipient rivers. The analytical protocol presented may be used for more in-depth studies on the occurrence and fate of these commonly used pharmaceuticals in the sewage treatment plants and in the aquatic environment.