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

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 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). Ispitana je reakcija Pd(II) i 1,8-dihidroksi-2-(pirazol-5-ilazo)-naftalen-3,6-disulfonske kiseline sorbovane na jonoizmenjivackoj smoli Dowex 1-X8, u cilju razvijanja apsorpciono-spektrofotometrijske metode za odredjivanje niskih koncentracija Pd(II) u vodi. Imobilizovani reagens sa Pd(II) gradi kompleks sastava 1:1, sa apsorpcionim maksimumom na 650 nm. Odredjeni su otpimalni uslovi reakcije (pH talasna duzina, vreme kontakta) za datu kolicinu sorbovanog reagensa. Dobijena je linearna zavisnost apsorbancije od koncentracije Pd(II) u oblasti od 5x10-6 ? 5x10-5 M, 5x10-7 ? 5x10-6 i 2.5x10-8 ? 2.5x10-7 M za sisteme cija je zapremina 10, 100 i 200 ml. Nadjeno je da je detekcioni limit za uzorke zapremine 200 ml 2.5x10-7 M Pd(II). Vecina metalnih jona, osim Cu(II) nema uticaj na kalibracioni grafik pri koncentracijama 100 puta vecim od koncentracije Pd(II).