Humic Acids Pyrolyzed onto Silica Microparticles for Solid-Phase Extraction of Benzotriazoles and Benzothiazoles from Environmental Waters

Abstract

This work focuses on the extraction and determination of contaminants of environmental concern belonging to the classes of benzotriazoles and benzothiazoles from tap and raw river water samples. The sorbent, recently proposed by this research group, prepared by pyrolysis of humic acids (HAs) onto silica microparticles (HA-C@silica), was tested for fixed-bed SPE of benzotriazole and benzothiazole compounds by modulating its sorption affinity through the carbon loading. This was successfully increased from 10 to 20 wt% HAs and the obtained material, characterized by different techniques, provided quantitative adsorption at the sample native pH (7.5–8), for 50–250 mL samples spiked with each compound at the micrograms per litre levels. After extraction, the analytes were simultaneously desorbed by 4 mL methanol, even more reducible to small volume before HPLC–HESI-MS/MS analysis. Recovery was satisfactory for all compounds, ranging from 70 to 114%, with RSD values ≤ 16% (n = 3). The developed procedure allows quantitation of benzotriazoles at concentrations far below the environmental trigger limits. HA-C@silica turned out to be appealing in comparison with the commercial sorbents in terms of cost, recovery and pre-concentration for determination of such pollutants in actual surface waters. Good reproducibility was observed on independent HA-C@silica preparations.