Anion Exchange Solid Phase Extraction of Humic Substances for the Determination of Complexed Heavy Metals in Natural Waters with High Dissolved Organic Carbon Contents

Abstract

A solid phase extraction material based on a copolymer of styrene and divinylbenzene was developed for the extraction of heavy metals complexed by humic and fulvic acids in water. The sorbent was synthesized by a modi®ed multistep activated swelling polymerization procedure; anion exchange functionalities were introduced by chemical modi®cation or by coating of the particle surface. These materials allowed the extraction of humic substances from water samples at their natural pH. The extract or the sorbent containing the humic substances was digested by dry ashing with sulfuric acid, and the metals Cu, Zn, Pb, and Cd were determined by differential pulse anodic stripping voltammetry. With this method, the four metals could be determined with recoveries between 87 and 99% at concentrations down to 50 ng/l.