Liquid phase microextraction and ultratrace determination of cadmium by modified graphite furnace atomic absorption spectrometry

A powerful microextraction technique was used for determination of cadmium in water samples using liquid phase microextraction (LPME) followed by graphite furnace atomic absorption spectrometry (GF-AAS). In a preconcentration step, cadmium was extracted from a 2 ml of its aqueous sample in the pH 7 as 5,7-dibromoquinoline-8-ol (DBQ) complex into a 4 μl drop of benzyl alcohol. After extraction, the micro drop was retracted and directly transferred into a graphite tube modified by [W.Rh.Pd](c). Some effective parameters on extraction and complex formation, such as type and volume of organic solvent, pH, concentration of chelating agent, extraction time and stirring rate were optimized. Under the optimum conditions, the enrichment factor and recovery were 450% and 90%, respectively. The calibration graph was linear in the range of 0.008-1 μg L-1 with correlation coefficient of 0.9961 under the optimum conditions of the recommended procedure. The detection limit based on the 3Sb criterion was 0.0035 μg L-1 and relative standard deviation (RSD) for eight replicate measurement of 0.1 μg L-1 and 0.4 μg L-1 cadmium was 5.2% and 4.5%, respectively. The characteristic concentration was 0.0032 μg L-1 equivalent to a characteristic mass of 12.8 fg. In order to evaluate the accuracy and recovery of the presented method the procedure was applied to the analysis of reference materials and seawater.