ANION-EXCHANGE SOLID-PHASE EXTRACTION OF HUMIC SUBSTANCES FOR THE DETERMINATION OF COMPLEXED HEAVY-METALS IN NATURAL-WATERS WITH HIGH DISSOLVED ORGANIC-CARBON CONTENTS

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