Sorption-spectrophotometric method for the determination of Pd(Ⅱ) in aqueous solutions

摘要

The reaction of Pd(Ⅱ) with 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphtha-lene-3-6-disulphonic acid (PACA) sorbed onto Dowex 1-X8 ion-exchange resin was investigated with the aim of developing an absorption-spectrophotometric analytical method for the determination of low Pd(Ⅱ) concentrations in water. The immobilized reagent formed a 1:1 complex with Pd(Ⅱ) having an absorption maximum at 650 nm. Parameters, such as pH, wavelength and contact time were optimised for a given amount of the sorbed reagent. The linearity range of absorbance vs. Pd(Ⅱ) concentration extended from 5x10~(-6) - 5x10~(-5) M, 5x10~(-7) - 5x10~(-6) and 2.5x10~(-8) -2.5x10~(-7) M when using 10,100 and 200 ml of sample solution, respectively. With a 200 ml sample, the detection limit was 2.5x10~(-7) M Pd(Ⅱ). Most metals, except Cu(Ⅱ), did not interfere when present in up to 100 times the concentration of Pd(Ⅱ).