A Simple Test to Determine the Propensity of a Sample of Leather to the Formation of Chromium (VI)

Abstract

Since the EU Commission Regulation of chromium(VI) in leatherarticles, there is a huge demand of analyses and controls in theleather sector for this parameter.However, for many tanners and leather dealers, the necessary costto have a laboratory capable to carry out the analyses according toan ISO method is not affordable.An easy test has been developed to carry out a screening of a leathersample in order to check out its compliance with the Cr(VI)restriction. This test is able to distinguish leathers that containchromium(VI) or show signs of tendency to develop it, from leathersthat even after thermal ageing exposure remain free of it.The test is based on the scientist principle of the ISO 17075-1method. Some operations of this Standard have been adapted withthe aim of saving costs and simplifying and shortening theworkload of the test. The essential criterion of this adaptation hasbeen that the developed test does not lead to false negatives.The only required devices are a laboratory oven, a balance of 0.01gof resolution, and a shaker. Neither a spectrophotometer nor acolorimeter is necessary.The method has four main steps. The first one is an ageing processat 80°C during 24 hours. After cooling down for 30 minutes, thesample is extracted for one hour, using an overhead rotatoryshaker or a magnetic stirrer. The third step is the discoloration ofthe extract, to remove the dyes of the colored solution so as toeliminate interferences. Finally, the extract is assessed by visualcolorimetry. The workload per sample is about 40 minutes.So far, more than 300 samples of leather have been tested. The kitperformed very well and only gave 5% of false positives. The kitdid not commit any false negative.