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

摘要

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 l-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-CLS), 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~(-1) of 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.