Determination of hexavalent chromium in cement by the use of HPLC-ICP-MS, FPLC-ETAAS, spectrophotometry and selective extraction techniques

Abstract

Due to the high toxicity of hexavalent Cr, an European directive has recently been issued limiting the content of water-soluble Cr(VI) in cement to a maximal concentration of 2 mg kg⁻¹. In order to fulfil the legislative requirements, it is often necessary to use reducing agents to lower the content of hexavalent Cr in cement. In the present work the abilities of HPLC-ICP-MS, FPLC-ETAAS, spectrophotometry and selective extraction procedure were estimated for the determination of Cr(VI) in aqueous cement extracts, containing high and low Cr(VI) concentrations. After comparison of the analytical performances of the different analytical methods used, water extracts of different cement samples were analysed. A good agreement was obtained for cement samples containing Cr(VI) concentration higher than 6 mg kg⁻¹. Differences between techniques in general did not exceed 10%. With the exception of selective extraction all techniques applied are accurate (recoveries of spiked samples lay between 95–103%) and of adequate sensitivity. The MIBK extraction procedure exhibited limitations in cement samples that were treated with reducing agents due to the gel formation in the organic phase. Because of its accuracy, high sensitivity and the high speed of the analysis, the HPLC-ICP-MS procedure could be recommended as a technique of choice. However, FPLC-ETAAS and spectrophotometry may also be applied for the determination of Cr(VI) in cement samples and cement samples treated with reducing agents.