Spectroscopic measurement of trivalent and hexavalent chromium

Human health and considerate approach to the environment are very topical nowadays. Both are inseparably related to the waste of leather industry management and their efficient processing. The research dealing with the automation of process control of complex hydrolytic processing of tannery waste materials has been solved in a long term scale on our faculty. In this paper a contribution to this issue concerning spectroscopic measurement of two prevalent forms of chromium is presented. Trivalent chromium is largely beneficial, whereas compounds of hexavalent chromium are classified as carcinogens. Salts of trivalent chromium participate within the process of the most widely used method for tanning the hides. Risk of chromium-containing materials consists in the possibility of spontaneous oxidation of compounds of trivalent to hexavalent chromium compounds. In terms of thermodynamics, this conversion is possible due to the values of the free enthalpy for the oxidation reactions. The direct contact of hexavalent chromium with the human body can cause serious health problems. For the analysis two spectroscopic methods were used. UV-VIS spectrophotometry as the most common method for detection chromium compounds in liquids and their quantitative evaluation and an innovative method Raman spectroscopy. Raman spectroscopy was used for the study of valence of chromium compounds contained in leather samples, shavings and dry matter of collagen hydrolysate as an efficient tool for material identification. Raman spectroscopy brings advantages over traditional laboratory techniques in terms of effective, rapid, non-contact and reagent-free way of measurements. The possibility to distinguish trivalent and hexavalent chromium was proved. For the samples performing luminescence Surface Enhanced Raman Spectroscopy was applied. The results show that Raman spectroscopy is a potential technique for hazardous hexavalent chromium detection with the benefit of direct determination ofvalences.