A robust method to quantify pharmaceuticals for the United Nations endorsed Global Estuaries Monitoring (GEM) Programme

Following human and animal consumption, pharmaceuticals often remain incompletely metabolized, entering aquatic ecosystems via sources like wastewater discharges, landfill leachates , and aquaculture farms, thereby eventually reaching the ocean through estuaries . This influx poses a significant threat to marine ecosystems. The Global Estuaries Monitoring (GEM) Programme, endorsed by the United Nations Decade of Ocean Science for Sustainable Development (2021−2030), aims to establish a standardized method for monitoring pharmaceuticals in the world's estuaries. This study was performed for simultaneously quantifying 65 pharmaceuticals in small-volume of water samples. The findings revealed that using 20 mL water yielded optimal recoveries between 60 % and 130 %. The influence of pH, salinity and sample matrix on the performance of the method was minimal. 45–50 pharmaceuticals remained stable over a seven-day storage period at both 4 °C and 25 °C. This cost-effective and user-friendly method paves the way for the GEM Programme to monitor pharmaceuticals in over 100 estuaries worldwide. • GEM Programme monitors pharmaceuticals in global estuaries via a standardized method • The method can detect and quantify 65 pharmaceuticals in 20-mL water samples. • Recovery of target compounds is minimally affected by salinity, pH and sample matrix. • Most pharmaceuticals remain stable in water samples for up to 7 days at 4 and 25 °C.