A Sorption Gel with Titanium Dioxide for Mercury Determination by the Technique of Diffusion Gradient in Thin Film

Abstract

A new polyacrylamide sorption gel with titanium dioxide has been tested as a new alternative for the determination of labile mercury species in aquatic systems by diffusive gradients in a thin film (DGT) technique. The deployment experiments in model solutions gave linear mass uptake over time corresponding to the Fick's 1^st law of diffusion. The titanium dioxide resin gel provides reliable results in the pH range 4–8, independently of ionic strength (1 mmol dm^–3 – 0.01 mol dm^–3 NaNO₃), which is a typical range for natural waters. The formation of strong and stable complexes of mercury ions with chlorides decreases DGT response and limits its application in seawater. In contrast, the interference of humic acids in the sorption of mercury on titanium dioxide resin gel is several orders of magnitude lower in comparison with the commonly used Chelex-100 based resin, which favorites the new resin gel.