Ionic liquid-based, single-drop microextraction for preconcentration of cobalt before its determination by electrothermal atomic absorption spectrometry

Abstract

An effective and environmentally friendly single-drop microextraction method was developed for the preconcentration of ultratraces of cobalt before its determination by electrothermal atomic absorption spectrometry (ETAAS). A microdrop of 1-hexyl-3-methylimidazolium hexafluorophosphate, [C 6MIM][PF6] was used to extract Co(II) ions as an ammonium pyrroldinedithiocarbamate (APDC) complex. The sensitivity was improved by increasing the volume of the suspended drop. Several variables affecting microextraction efficiency and the ETAAS signal-such as pyrolysis and atomization temperature, pH, APDC concentration, extraction time, drop volume, and stirring rate-were investigated and optimized. Under the optimum experimental conditions, the detection limit (3 SD) was 0.04 μ/L, and the enrichment factor was 120. The RSD for five replicate determinations of Co(II) at 0.5 μ/L was 4.5%. The developed method was validated by analysis of a Standard Reference Material and applied to the determination of cobalt in water samples.