Exploring preconcentration procedures based on trioctylmethylammonium thiosalicylate (TOMATS) to facilitate mercury detection in natural waters

Abstract

Mercury, Hg, is a hazardous contaminant that is present in the environment because of natural and anthropogenic sources. Due to its high toxicity and its presence in aquatic systems, it is important to develop methodologies to control its existence in the environment. In this study we have developed preconcentration procedures using the Task Specific Ionic Liquid (TSIL) trioctylmethylammonium thiosalicylate (TOMATS) to facilitate the detection of mercury in natural waters. Two different approaches have been investigated: the incorporation of TOMATS in a polymer inclusion membrane and its use to impregnate solid sorbents. In the case of PIMs, we first investigated the effect of membrane composition. For that, different membranes were prepared using cellulose triacetate (CTA) or polyvinylchloride (PVC) as polymers, TOMATS as a carrier, and different plasticizers bearing long aliphatic chains, and were incorporated in a special device to perform Hg preconcentration. 50% CTA+ 30% TOMATS+ 20% NPOE membrane was used for the following studies. The effect of other metals on Hg transport was evaluated. It was observed that all metals were transported through the PIM and were preconcentrated in the stripping phase. Using this PIM-device an application with different natural waters showed that it is a good procedure to preconcentrate Hg. Also, novel sorbents based on silicon dioxide (SiO2) nanoparticles and cellulose powder were modified with TOMATS in order to design extraction studies and elution with cysteine. They were compared with non-impregnated sorbents and it was observed that in both cases the extraction was really efficient, showing that the impregnation was done successfully. It was observed that its kinetics is fast. These experiments were also performed with less amount of impregnated sorbent and different volumes in order to calculate their capacity of mercury extraction. The impregnated sorbents were also studied, in terms of extraction and elution, incorporated in a gel of agarose, the binding gel of the DGT technique, without losing extraction efficiency towards mercury