Preconcentration of trace amounts of silver and cadmium by ion exchange and micro-extraction from water for flame atomic absorption spectrometry
A method based on a combination of ion exchange and micro-extraction is suggested for preconcentrating silver and cadmium from lake water. These metals were sorbed on a mini-column loaded with a strongly basic anion-exchange resin in the form of halide complex anions, and then silver was eluted with 6 mol l–1 hydrochloric acid and cadmium with 2 mol l–1 nitric acid. The metals were further concentrated into 0.2 ml of butyl acetate with potassium iodide and Zephiramine as extraction agents. For flame atomic absorption spectrometric determination, 20 µl of the organic phase were nebulized. Optimum conditions for ion exchange and liquid–liquid extraction were established, and data on interferences, precision and detection limits were determined. Using calibration graphs, the contamination level of cadmium in preconcentration processes was also estimated. Sub-µg l–1 levels of silver and cadmium in water could be determined with a concentration factor of 10 000 by the proposed method.