Determination of nickel using cold-induced aggregation microextraction based on ionic liquid followed by flame atomic absorption spectrometry

Cold-induced aggregation microextraction (CIAME) combined with flame atomic absorption spectrometry (FAAS) was applied to preconcentration and determination of nickel(II) ions in natural water samples. The proposed method used 1-hexyl-3-methylimidazolium hexafluorophosphate (Hmim]PF ₆ ]) as the extraction solvent and 1-(2-thiazolylazo)-2-naphthol (TAN) as the complexing agent. The extraction solvent was dissolved in the sample solution at 45°C. After dissolving, the solution was cooled in the ice bath and a cloudy solution of IL fine droplets was formed due to the decrease of IL solubility. After centrifugation, the fine droplets of extractant phase were settled at the bottom of the conical-bottom centrifuge tube. Analysis was carried out by a FAAS. Several important parameters influencing the CIAME extraction efficiency such as pH, complexing agent concentration, extraction solvent volume, salt effect, solution temperature, extraction time, centrifugation time and heating time were investigated and optimized. Under the optimum conditions, the limit of detection (LOD) was 0.8 ng/mL, and the relative standard deviation (RSD) was 3.4% for 50 ng/mL of nickel. The performance of the method was evaluated for extraction and determination of nickel in tap, mineral and seawater samples, and satisfactory results were obtained.