IN-LINE ULTRAVIOLET-DIGESTION OF NATURAL-WATER SAMPLES FOR TRACE-METAL DETERMINATION USING AN AUTOMATED VOLTAMMETRIC SYSTEM

The use of in-line UV-digestion for breakdown of dissolved organic mat ter (DOM), prior to voltammetric determination of trace metals in natu ral samples, is discussed in this paper. Destruction of DOM is necessa ry to free trace metals that are organically complexed and to remove i nterfering organic surfactants. Complete breakdown of DOM in natural w ater samples is achieved by in-line UV-digestion using a 100 W medium pressure mercury vapour lamp and a silica coil, at a sample digestion time of 4.5 min. The efficiency of the system is tested with destructi on of humic acid, conversion of Cr(III) to Cr(VI), and the release of Ni and Cu from organic complexes in sea water. The in-line application of UV is illustrated by automated voltammetry of nanomolar levels of Cu and Ni in samples from oceanic origin.