Binary colorimetry in chemical analysis of drinking, natural, and waste water: comparison with photometry

The article presents the results of a comparative study on the applicability of binary colorimetry versus photometry in the chemical analysis of drinking, natural, and waste waters for iron (II, III), nickel (II), and copper (II) contents. Sample preparation was identical for both methods under consideration. For digital photography of the solutions analised a mobile device under controlled conditions was used. To minimize external light interference, photography was conducted in a darkened room. An assessment of the influence of scattered light showed no significant contribution to the colorimetric measurement results. The obtained images were processed using specialized software and converted to a binary format, subsequently determining the binarization threshold, which was used as the analytical signal. It was found that the relative standard deviations of the results obtained by binary colorimetry and photometry do not exceed 0.12 and 0.06, respectively. Two-way analysis of variance revealed no statistically significant differences in the accuracy of the methods under consideration. However, their difference was demonstrated at different concentration levels of Fe, Ni, and Cu. It was established that in the concentration ranges of 0.10 – 2.00 mg/L Fe, 0.02 – 0.10 mg/L Ni, and 0.25 – 1.50 mg/L Cu, the sensitivity characteristics of binary colorimetry are predictably inferior to those of photometry. It was shown that for the colorimetric determination of Fe (II, III), Ni (II), and Cu (II) at concentration levels close to the detection limits of these ions, the analyzed water sample should be preconcentrated. The results of the conducted study indicate that binary colorimetry can be considered an accessible alternative in the absence of a photometer for the determination of Fe (II, III), Ni (II), and Cu (II) in water.

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