Solid phase extraction of cadmium on 2-mercaptobenzothiazole loaded on sulfur powder in the medium of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and cold vapor generation–atomic absorption spectrometric determination

Abstract

A novel solid phase extractor for preconcentration of cadmium at ng L −1 levels has been developed. Cadmium ions were retained on a column packed with sulfur powder modified with 2-mercaptobenzothiazole (2-MBT) in the medium of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] +PF 6 −) ionic liquid. The presence of ionic liquid during modification of sulfur enhanced the retention of cadmium ions on the column. The retained cadmium ions were eluted with 2 mol L −1 solution of HCl and measured by cold vapor generation–atomic absorption spectrometry (CVG–AAS). By using reaction cell-gas liquid separator (RC-GLS), gaseous cadmium vapors were produced and reached the atomic absorption spectrometer, instantaneously. The influence of different variables on both processes of solid phase extraction and CVG–AAS determination of cadmium ions was investigated. The calibration curve was linear in the range of 10–200 ng L −1of cadmium in the initial solution with r = 0.9992 ( n = 8) under optimum conditions. The limit of detection based on three times the standard deviation of the blank (3S b, n = 10) was 4.6 ng L −1. The relative standard deviation (R.S.D.) of 25 and 150 ng L −1 of cadmium was 4.1 and 2.2% ( n = 8), respectively. The procedure was validated by the analysis of a certified reference material (DORM-3), water and fish samples.