Abstract
Developments in the liquid micro-extraction of trace metals from aqueous phases have proven to be limited when extended from pure water to more complex and demanding matrices such as sea water or wastewater treatment effluents. To establish a system that works under such matrices, we successfully tested three task-specific ionic liquids, namely trihexyltetradecyl- phosphonium-, methyltrioctylphosphonium- and methyltrioctylammonium 3-hydroxy-2-naphthoate in two-phase solvent bar micro-extraction (SBME) experiments. We describe the influence of pH, organic additives, time, stirring rate and volume of ionic liquid for multi-elemental micro-extraction of Cu, Ag, Cd and Pb from various synthetic and natural aqueous feed solutions. Highest extraction for all metals was achieved at pH 8.0. Minimal leaching of the ionic liquids into the aqueous phase was demonstrated, with values < 30 mg L−1 DOC in all cases. Sample salinities of up to 60 g L−1 NaCl had a positive effect on the extraction of Cd, possibly due to an efficient extraction mechanism of the present chlorido complexes. In metal-spiked natural feed solutions, the selected SBME setups showed unchanged stability under all conditions tested. We could efficiently (≥85%) extract Cu and Ag from drinking water and achieved high efficacies for Ag and Cd from natural sea water and hypersaline water, respectively. The method presented here proves to be a useful tool for an efficient SBME of heavy metals from natural waters without the need to pretreat or modify the sample.
Highlights
In view of the ongoing pollution of waterbodies with heavy metals from anthropogenic sources and the rise of emerging pollutants such as silver [1,2,3], research in adapting extraction methods to meet these challenges is increasingly important [4]
We describe the effects of varying physico-chemical parameters in the
Organic additives are generally used in solvent bar micro-extraction (SBME) to increase the diffusion of metals into the fiber lumen when utilizing viscous task-specific ionic liquids (TSILs)
Summary
In view of the ongoing pollution of waterbodies with heavy metals from anthropogenic sources and the rise of emerging pollutants such as silver [1,2,3], research in adapting extraction methods to meet these challenges is increasingly important [4]. Several studies have incorporated micro-extraction approaches, highlighting liquid- or solid-phase micro-extraction setups for trace metals [7,8]. Despite their potential for green extraction, liquid micro-extraction methods still require improvement for their application to natural- and to saline waters. This is due to the lack of efficient extractants and organic solvents that offer sufficient stability during extraction [9,10]
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