Vapor generation atomic absorption spectrometric determination of cadmium in environmental samples with in-line anion exchange separation

A novel in-line anion exchange separation method is described for the removal of Mn²⁺, Fe³⁺, Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺, and Pb²⁺ from Cd²⁺ and for its subsequent determination by vapor generation atomic absorption spectrometry. High Cd²⁺ retention efficiency and maximum exclusion of other metal ions were achieved by using Cl^-, Br^-, or I^- loaded strong base anion exchange resin and fiber in chloride medium. SO₄ ^2- and NO₃ ^- affected the retention of Cd²⁺ on Cl^- or Br^- loaded exchangers but were beneficial for elution from I^- loaded exchangers. Fast and efficient elution from the exchangers was achieved by using ethylenediamine solution. The removal of Zn²⁺ was unnecessary as it prevents a decline in the sensitivity of cadmium response when ethylenediamine and high acid concentration were used. Under optimum conditions, the achievable detection limits (3σ) with sample loadings of 0.48 and 9.6 mL were 40 ng L^-1 and 3 ng L^-1, respectively. Interference of residual organic matrix, in sample digests, with the separation and retention of cadmium were eliminated by use of microwave assisted digestion. The method was successfully applied to the determination of Cd in river sediment, fish liver, and water samples.