Application of a dispersive micro-solid-phase extraction method for pre-concentration and ultra-trace determination of cadmium ions in water and biological samples

A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic-assisted dispersive micro-solid-phase extraction (UA-D-SPE) was developed. Silica-coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X-ray diffraction. Following UA-D-SPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box-Behnken design was used for optimization of important sorption and desorption parameters in UA-D-SPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3min; sorption amount, 35mg; type and concentration of eluent, HCl and 1.1mol l(-1); volume of eluent, 360 l; sonication time for desorption, 110s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA-D-SPE were found to be 0.8ng l(-1) and <6%, respectively.