Development of sol-gel silica-based mixed-mode zwitterionic sorbents for determining drugs in environmental water samples

Four novel mixed-mode zwitterionic silica-based functionalized with strong moieties sorbents were synthesized and evaluated through solid-phase extraction (SPE) to determine acidic and basic drugs in environmental water samples. All sorbents had the same functionalization: quaternary amine and sulfonic groups and C 18 chains so that hydrophobic and strong cationic exchange (SCX) and strong anionic ex-change (SAX) interactions could be exploited, in addition, two of them had carbon microparticles embedded. All sorbents retained both acidic and basic compounds in the preliminary assays but only the basic compounds were retained selectively through ionic exchange interactions when a clean-up step was introduced. The SPE method was therefore optimized to promote the selective retention of the basic compounds, initially with the two best-performing sorbents. After optimization of the SPE protocol, these sorbents were evaluated for the analysis of environmental water samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method with the best-performing sorbent was then validated with 100 mL of river samples and 50 mL of effluent wastewater samples in terms of apparent recoveries (%R-app) spiking samples at 50 ng/L (river) and 200 ng/L (river and effluent), matrix effect, linear range, method quantification and detection limits, repeatability, and reproducibility. It should be highlighted that %R-app ranged from 40 to 85% and matrix effects ranged from -17 to -4% for spiked river samples. When the method was applied to river and effluent wastewater samples, most compounds were found in the range from 24 to 1233 ng/L with detection limits from 1 to 5 ng/L. (C) 2022 The Authors. Published by Elsevier B.V.

Automated summary

In this study, four novel mixed-mode zwitterionic silica-based sorbents were synthesized and evaluated for the determination of acidic and basic drugs in environmental water samples. The sorbents showed effective retention of both acidic and basic compounds, with selective retention of basic compounds achieved through ionic exchange interactions. The optimized solid-phase extraction (SPE) method using the best-performing sorbents was validated for the analysis of river and effluent wastewater samples, demonstrating satisfactory recoveries, low detection limits, and good repeatability and reproducibility.