The Determination Of Hexavalent Chromium As A Requisite To Comply With The Packaging Directive (In Italian)

EC Directive 94/62 imposes the concentration limits of heavy metals such as Pb, Cd, Hg and hexavalent chromium in packaging materials starting 30 June 1998. In the absence of a standard procedure, this paper describes a method which allows the eventual presence of hexavalent chrome to be detected and measured also in glasses with a high content in trivalent chromium, to which it is sometimes erroneously assimilated. The glass sample is decomposed in a cold mixture of H2SO4 and NH4HF2. By adding diphenylcarbazide a pink coloured comples is obtained, whose absorbance is measured at 840nm. The detection limit is 5ppm Cr03 (mg/Kg glass).