SELECTIVE SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF CHROMIUM(VI) USING A FLOW-INJECTION SYSTEM WITH A MICROCOLUMN OF ZIRCONIUM(IV) OXIDE MODIFIED SILICA-GEL

Zirconium(IV) oxide coated on a silica gel surface was found to be very effective for extracting Cr(VI) from aqueous solutions at a pH of about 3. A microcolumn packed with this material was inserted into a flow injection system for the separation and preconcentration of Cr(VI). By this process, a concentration level of 2 ppb was detected with a relative standard deviation of 2.4%. Because of the high selectivity of the immobilized substrate, it was possible to determine Cr(VI) in the presence of larger amounts of other ions. The analysis was also carried out on natural water spiked with Cr(VI), and compared with a standard method.