Sample Pretreatment in Determination of Anions in Mine Waters with High Iron Contents

Abstract

Reliable analysis of anions in mine waters with high iron and sulfate contents is important for their characterization. However, both traditional and LC methods failed in direct anion analysis. The article describes two sample pretreatments – alkalization and cation exchange. The pretreated water samples were analyzed by potentiometric titration, spectrophotometry, ion chromatography with conductivity detector in suppressed regime and HPLC with diode array detector using indirect UV detection at 260 nm. Both the sample pretreatments enable determination of some anions, the former procedure being more suitable for the purpose. Potentiometric titration and spectrophotometry seem to be the most suitable due to low detection limits for all the selected anions ranging from 0.4 to 1.8 mg l^–1. The application of ion chromatography and liquid chromatography with diode array detector for the purpose is also possible. However, due to very high detection limits of samples pretreated by cation exchange (26–121 mg l^–1) and low recoveries of samples pretreated by alkalization (<17 %) for all the selected anions, HPLC‑DAD is not suitable for analysis of real samples. Validation and analytical characteristics of the methods are given and discussed.