Speciation and determination of trace lead : methodology development and analysis of natural waters using Chelex-100 and GFAAS

The development of a method for speciation, preconcentration, and determination of lead was successfully conducted using Chelex-100 and graphite furnace atomic absorption spectroscopy (GFAAS). Sorption under static conditions and direct measurements in the bead slurry or after fast elution of lead from beads with HNO3 solution was used. The effects of buffers, sorption kinetics, filtration criteria, sample concentration, resin particle size and temperature program for the GFAAS were carefully studied. In this study, synthetic aqueous samples containing lead were preconcentrated under static conditions using the ion exchange resin, Chelex-100, and the resin was directly analyzed using GFAAS. The batch preconcentration process was optimized using 250 ml (0.3 ppb Pb) of synthetic lead sample with addition of 0.25g Chelex-100, buffered at pH=5.0 and sorption for 1.5 hours under magnetic stirring. The Chelex-100 resins were separated from the equilibrated solution by filtering under vacuum. Nitric acid (5 ml, 5% v/v) was then used to desorb lead from Chelex-100 resins. Three natural waters, lake, canal and river waters were studied, comparing the Chelex-100 with evaporation methods. The distribution of lead species among suspended solids, colloids or complexes, and ionic form was successfully differentiated with this combination method