Abstract
A simple and rapid semiquantitative procedure has been developed for the determination of sub-ppm level of cadmium in environmental aquatic samples by using an analytical micro-column packed with reagent gel beads. Reagent gel beads were prepared by treating the cross-linked polystyrene beads {2 % divinylbenzene, (70100)mesh in dry condition} with 0.02 % chlorobenzene solution of 6-brormo-2-benzothiazolylazo-2-naphthol (BTAN) for 24 h at room temperature. The gel beads were packed into a glass column (2.5 mm bore, 120 mm length). When a sample solution containing cadmium, buffered to pH 10 with Clark-Lubs buffer, was passed through the BTAN gel column at a flow rate of 0.2 ml/min, the original pink color of the reagent gel turned to redviolet from the up-stream of the column. As the length of colored band was proportional to the total amount of cadmium in the sample solution passed through the column, the concentration of cadmium can be determined from the calibration line which had been prepared by using the standard solution. Cadmium ion at (0.050.1) ppm and (0.20.5) ppm levels could be determined with ± 10 % and ±5 % relative errors, respectively. Of the foreign metals, 40-fold excess of Cr (VI), 20-fold excess of Al and Ni, 10-fold excess of Co (II), Hg(II), Fe (III) and Ag, and 5-fold excess of Cu (II) could be masked with Zincon, Tiron, thiourea and sodium fluoride. As for Zn (II), interferences could be masked up to identical amount with Cd with Zincon. This method was successfully applied to the analysis of cadmium in environmental aquatic samples.
