Multi-class determination of pharmaceuticals as emerging contaminants in wastewater from Eastern Province, Saudi Arabia using eco-friendly SPE-UHPLC-MS/MS: Occurrence, removal and environmental risk assessment

Occurrence of pharmaceuticals in wastewater, which might be released to different water environments causing contamination might lead to health hazards. Therefore, sensitive, selective and reliable analytical methods are required to monitor pharmaceuticals in such complex environmental matrix. In this work, an eco-friendly, sensitive, robust and selective ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) method was developed to simultaneously identify and quantify multiple classes of pharmaceuticals in influent and effluent wastewater samples in Eastern Province, Saudi Arabia using solid phase extraction (SPE) for sample preparation. The extraction conditions were optimized to achieve the best extraction efficiencies and achieved recoveries of 70.4 – 112.2% and 74.0 – 107.8% in influent (IWW) and effluent wastewater (EWW) samples, respectively. The optimized method had satisfactory precision represented as %RSD lower than 13.04%. Limits of detection were 0.06 – 16.0 and 0.07 – 13.23 ng L^-1 for IWW and EWW, respectively. The developed method was successfully employed for the analysis of 32 pharmaceuticals in wastewater. The greenness profile was assessed using two assessment tools; Analytical Eco-scale and AGREE metric. Caffeine and Ciprofloxacin were the most frequent and highest concentration in influent wastewater with concentration range 23,600 – 37,602 ng L^-1 and 1,684 –3,585 ng L^-1, respectively. Average effluent concentrations range was from below method quantification limit to 1,241 ng L^-1 (ciprofloxacin). Removal efficiency ranged from - 3.1% (trimethoprim) to 99% (caffeine). Environmental risk assessment was calculated using risk quotient approach for each individual analyte and for the mixture. The results revealed 4 and 6 compounds with high and medium risk, respectively. This work provides new insights into the occurrence, removal and ecotoxicological risk of pharmaceuticals from wastewater in Eastern Province, Saudi Arabia. It emphasizes the importance of monitoring these compounds as an input for future mitigation actions.