Separation of picogram quantities of Cr( iii ) and Cr( vi ) species in aqueous solutions and determination by graphite furnace atomic absorption spectrometry

A procedure was developed for the separation and independent determination of picogram quantities of Cr(III) and Cr(VI) in aqueous solution. Cr(VI) was adsorbed onto iron-loaded activated charcoal (FeC*), while Cr(III) was left in the filtrate and was measured directly by graphite furnace atomic absorption spectrometry (GFAAS). The Cr(VI) adsorbed on FeC* was released with 2.0 M HCl before measurement by GFAAS. The detection limits were 7.0 pg for total Cr, 1.9 pg for Cr(III) and 6.8 pg for Cr(VI). The recoveries were 98 ± 4 for total Cr, for Cr(III) 97 ± 3 and for Cr(VI) 101 ± 7. The procedure was tested with the Ground Water and Waste Pollution Control Check Standard WP-15 spiked with Cr(VI) and with samples from the plating industry.