Preparation of Zwitterionic Silica‐Based Sorbents for Simultaneous Extraction of Acidic and Basic Pharmaceuticals From Water Samples

The sol‐gel approach was applied to develop three homemade silica sorbents. These sorbents where functionalized with mixed‐mode zwitterionic exchange groups using only one additive to introduce at once the strong cation‐ (sulfonic groups) and strong anion‐exchange (quaternary amines) moieties. The developed materials were applied for the solid‐phase extraction (SPE) of basic and acidic pharmaceuticals, and the sorbent functionalized with 2‐(methacryloxy)‐ethyldimethyl‐3‐(sulfopropyl)ammonium hydroxide was the best performing one. The optimal conditions for SPE were pH 5, a variable loading volume (ranging from 25 to 100 mL depending on the complexity of the sample) and elution volume with 5 mL of 1% NH 4 OH in MeOH. The method validation was carried out attending to apparent and relative recoveries, matrix effect, precision (intraday and interday), and detection and quantification limits. It can be highlighted that apparent recoveries were higher than 30% for most compounds and method detection limits were at the low ng/L. The validated method was applied to quantify the pharmaceuticals in environmental water samples.