Non-chromatographic speciation of arsenic by successive dispersive liquid-liquid microextraction and in situ formation of an ionic liquid in water samples

Abstract

Arsenic is an element present in waters in its different species which can cause a serious risk to human health due to the consumption of these waters. However, the toxicity of each species is very different. Because of that, in analytical chemistry there is a great interest in developing methods that allow the quantification of low concentrations and speciation of arsenic. Accordingly, this work introduces a novel method applied to determine very low concentrations of arsenic species (As (III), As (V), monomethylarsonic acid (MA), dimethylarsinic acid (DMA) and arsenobetaine (AB)) in water samples. The procedure provides high enrichment factors and great sensitivity in a simple and non-chromatographic way using electrothermal atomic absorption spectrometry. The in-situ formation of an ionic liquid (IL) results in a dispersion through the formation of a cloud of IL droplets that allows the instantaneous extraction of the arsenic species. After centrifugation, they can be quantified by direct injection of the extract (IL + arsenic species) into the detector. The different experimental conditions such as pH and the use of complexing agents allow the selective extraction of each species. An enrichment factor of 295 is obtained by using this procedure. Additionally, high sensitivity and a low detection limit (0.02 µg L−1) for all species are achieved, enabling the method as an alternative for the chromatographic techniques.