The effect of freshwater UV-irradiation prior to resin preconcentration oftrace metals

Trace metal concentrations in natural freshwater samples are often below de tection limits for determination by inductively coupled plasma-mass spectro metry (ICP-MS). This is especially so following size fractionation of the s ample. Preconcentration is therefore necessary, and sorption on a chelating resin such as Chelex-100 is often used. In order to chelate metals strongl y complexed with organics, the metal-organic association has to be severed. In this study, ultra violet (UV)-irradiation was used to oxidize organic m atter in a humic acid reference solution, and in a natural sample spiked wi th Ag, Cd, Cu and Ph, where the recoveries of the metals were calculated. E xcept for Ag, recoveries of Cd, Cu and Pb increased significantly up to alm ost 100% after irradiation. If preconcentration on Chelex-100 is used, W-ir radiation appears to be an essential step in achieving accurate concentrati ons of organically chelated trace metals in freshwater. (C) 1999 Elsevier S cience B.V. All rights reserved.