Estimation of Toxic Hexavalent Chromium (Cr6+) in Metal Components Present in Electronic and Electrical Materials with or without using Coordinating Ligands

Abstract

The aqueous solutions of toxic hexavalent chromium have been analyzed using diphenyl carbazide (DPC) dissolved in organic solvents as a coordinating ligand since early nineteen hundreds. The chemistry is not clear due to the formation of an unstable, suggested organometallic complex, which is only An intermediary. The structure of the same could not be determined or is hypothetical even today with a further suggested, molecular structure in which instead of pi bonded delocalization of benzene rings expected to be as in sandwich compounds, electron empty d-orbital of hexavalent chromium facilitating the electron transfer and giving the observed color of the obtained complex as in inner field coordinating complexes.  The electrical and electronic equipment requires the estimation of hexavalent chromium up to ~0.2 % (~2000 ppm) present in high chromium containing solid matrix, with DPC using standard International Electro-technical Commission (IEC) method. However, the visible yellow color can be directly measured on UV-Vis spectrophotometer with the hexavalent chromium stripped or leached out into acidic aqueous solutions from these materials using the known IEC method for leaching.  The presence of interfering ions is ruled out with the leaching procedure given in it. Therefore, the stability of these aqueous acidic solutions containing hexavalent chromium was checked for 16 days. So that direct measurement can be done without DPC. Screws, Fork Pivot Bore and Rat Trap Box containing hexavalent chromium were analyzed and compared with and without DPC. It is noted that the analysis of these materials can satisfactorily be achieved easily or simply without adding DPC on UV-Vis spectrophotometer or any other organic ligands or using high-end equipment such as Ion Chromatography (IC).