Application of a homemade silica-based mixed-mode ion-exchange sorbent for the determination of drugs in environmental water samples

Two homemade silica-based mixed-mode ion-exchange sorbents with strong moieties were compared for the solid-phase extraction (SPE) of a group of pharmaceuticals, drugs of abuse and metabolites. The difference between sorbents was the presence of graphene microparticles embedded in the network and the best results were obtained with the sorbent that did not contain graphene.The optimum SPE protocol of the non-graphene sorbent was: loading pH at 3, different loading volumes depending on the type of sample, 2 mL of MeOH as washing solvent.The optimized method was validated for the analysis of water samples of environmental interest (river water, effluent wastewater and influent wastewater). Apparent recoveries ranged from 22 to 68%, matrix effect values were lower than ±20 for most compounds, and method detection limits ranged from 1 to 28 ng/L and method quantification limits from 2 to 56 ng/L. Precision was obtained as percentual relative standard deviation (RSD%, n=4) and the repeatability and reproducibility between days were always lower than 18%.The sorbent was used to determine the analytes in environmental water samples, where most compounds were found in the range from 2 to 180 ng/L in river samples, from 3 to 2547 ng/L in effluent wastewater samples and from 24 to 8086 ng/L in influent wastewater samples.