A continuous approach for the determination of Cr(VI) in sediment and soil based on the coupling of microwave-assisted water extraction, preconcentration, derivatization and photometric detection

A dynamic system for the continuous leaching of Cr(VI) from sediment and soil based on both microwave assistance and iterative change of the flow direction of the extractant through the sample cell has been developed. The microwave-assisted extractor has been coupled to a photometric detector through a flow injection interface in order to develop a fully automated method. The Cr(VI) extracted was monitored after derivatization with 1,5-diphenylcarbazide. Two approaches are proposed which differ in the inclusion of a preconcentration minicolumn packed with a strong anion exchange resin. A 0.04 M ammonium buffer solution was used as extractant and 0.2 g of sample-river sediment spiked with 50 and 5 mug g(-1) for the method without preconcentration (method A) and with preconcentration (method B)-was subjected to 8-14 min of 300 W microwave-assisted extraction. The within-laboratory reproducibility and repeatability were 2.6 and 1.9 for method A, and 4.0 and 2.6 for method B. The proposed methods have been compared with the reference EPA method 3060/7196. (C) 2004 Elsevier 13N. All rights reserved.