Determination of the water-soluble chromate content

The European chromate directive 2003/53/EC stipulates that cements or cementitious mixtures must not contain more than 2 ppm water-soluble chromate relative to the dry cement mass.

In Germany, the chromium(VI) content can be determined either according to TRGS 613 (Technical Rules on Hazardous Substances) or according to EN 196-10 at present. Both methods provide for the photometric detection of the water-soluble chromate content by dyeing with diphenyl carbazide. They differ, however, in the way the chromate is extracted from the cements.

TRGS 613 describes an extraction process that consists of stirring 10 g cement with 40 g water for 15 minutes and subsequently filtering it out. The subsequent analysis is carried out either by measuring the acidified solution immediately, or following the reduction of oxidising constituents with bromine.

Analysis according to EN 196-10 consists of producing mortar according to EN 196-1. After filtering out the mortar suspension, the chromate content of the extract is determined photometrically.