Sensitive Assessment of Hexavalent Chromium Using Various Uniform and Non-uniform Color Space Signals Derived from Digital Images

Digital imaging using conventional camera, mobile phone camera, or computer scanner can be a convenient and low-cost approach for the highly sensitive assessment of hexavalent chromium in natural and waste waters. An aliquot sample containing Cr(VI) is reacted with diphenylcarbazide to yield a characteristic violet color. Image analysis of the violet-colored product gave the red, green, and blue (RGB) intensities that are converted into ten uniform and non-uniform color spaces and two color difference parameters, which are used and compared here, for the first time, as analytical signaling tools for the assessment of hexavalent chromium. Many of the acquired signals displayed outstanding analytical performance and statistically surpassed the regularly used RGB signals and competed well with signals of a sophisticated Shimadzu 1650 PC spectrophotometer. The sensitivity and simplicity and low cost of this strategy make it an outstanding competitor for commercial hexavalent chromium analyzers and advanced spectrophotometers. Graphical abstract