In the present study, a multi-residue method based on a bag –solid phase extraction (bag-SPE) technique was applied to determine the occurrence of ten pharmaceuticals in surface water close to the effluent of a sewage treatment plant (STP) and along a coastal gradient from a STP effluent.
The ten compounds selected were caffeine, atenolol, metoprolol, oxazepam, carbamazepine, ketoprofen, naproxen, ibuprofen, diclofenac and gemfibrozil, i.e. a mixture of pharmaceuticals of different therapeutic classes having logarithmic octanol/water partitioning coefficients (Log KOW) ranging from -0.13 to 4.39.
All analyses were performed using ultra performance liquid chromatography (UPLC) combined with quadrupole time-of-flight (QToF) mass spectrometry.
The detection limit (LOD) of the pharmaceuticals in water ranged from 1.0-13 ng/L. The method showed consistent linear concentration ranges from 25-800 ng/L with regression coefficients (R2) better than 0.9801. The recoveries of the selected analytes ranged from 10.6-64.5 % with relative standard deviations (RSD) of < 16.4 % and inter-day variations of less than 17.7 %.
Although the detection limits (LOD) of the analytes were low, only four of the selected ten pharmaceuticals (caffeine, metoprolol, oxazepam and carbamazepine) showed concentrations in surface water higher than the detection levels. The concentrations of the four pharmaceuticals in sea water range from 4-210 ng/L.