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

Abstract

The reaction of Pd(II) with 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene- 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 5×10-6 - 5×10-5 M, 5×10-7 - 5×10-6 and 2.5×10-8 - 2.5×10-7 M when using 10, 100 and 200 ml of sample solution, respectively. With a 200 ml sample, the detection limit was 2.5×10-7 M Pd(II). Most metals, except Cu(II), did not interfere when present in up to 100 times the concentration of Pd(II).