Selected pharmaceutical analysis in a wastewater treatment plant during COVID-19 infection waves in South Africa

Globally, an extensive range of pharmaceuticals are consumed daily to treat a variety of illnesses and diseases. Since the occurrence of the SARS-CoV-2 virus (COVID-19) outbreak, the use of pharmaceuticals has increased drastically in order to treat and prevent infection. Studies have shown that pharmaceutical usage is largely dependent on seasonal temperatures. This was explored in the present study and was verified by the results obtained. Versatile solid phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS) methods were developed and validated for the accurate detection of target pharmaceuticals. Method percentage recoveries ranged from 73.53-100.70%, while the limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.0330-0.886 mg L-1 and 0.0990-2.68 mg L-1, respectively. Resulting concentrations of pharmaceuticals used to treat chronic ailments such as diabetes, hypertension, tuberculosis and HIV/AIDS showed consistent daily usage while pharmaceuticals used for the treatment of COVID-19 and influenza showed distinct seasonal trends. Concentrations obtained for sulfamethoxazole hydroxylamine and sulfamethoxazole ranged from 0.05215-0.3438 mg L-1 and 0.009818-0.3002 mg L-1, respectively, while concentrations quantified for prednisolone and ivermectin ranged from 0.008775-0.4482 mg L-1 and 0.008520-0.979 mg L-1, respectively. Trends also directly correlated with the total number of active COVID-19 cases experienced in South Africa during sampling periods and this was confirmed using a one-way ANOVA test. P-values obtained for sulfamethoxazole hydroxylamine, sulfamethoxazole and ivermectin were below 0.05.