Cation-exchange Separation of Interfering Metals from Acid Mine Waters for Accurate Determination of Total Arsenic and Arsenic(iii) by Hydride Generation-atomic Absorption Spectrometry

INTRODUCTION Accurate and precise determination of inorganic As (III/V) redox species is important in the interpretation of its toxicity and mobility in acid mine waters. Several analytical methods use arsine generation to separate arsenic species but high metal concentrations can suppress arsine production (Creed and others 1996). The potential inhibition of arsine formation by eleven metal species including Cu, Fe(III), Fe(II), Al, Cd, Mn, Zn, Co, Ni, Cr(III), and Cr(VI) ranging in concentration from 0-1000 mg/L was investigated with a flow injection analysis system (FIAS) and detection by atomic absorption spectrometry. Interfering metal cation species can be removed with cation exchange resin while maintaining existing As(III)/As(T) ratios (As(T)=As(III+V)). The pre-analysis separation of Fe(III) using cation exchange resin for the determination of As redox species using ion chromatography in iron sulfate-sulfuric acid media has been successfully performed in the past (Tan and Dutrizac, 1985). Oxidation of As(III) by Fe(III) was also investigated.