Abstract

Background: Manganese, Mn, is an essential element that is present in steels, and determines steel’s mechanical properties. Traditionally, atomic absorption and X-ray photoelectron spectroscopic methods were used for Mn analysis and complicated instrument operations, sometimes of high cost, are associated, and spectrophotometry/colorimetry is another tool for Mn analysis with simple operations. Nowadays, smartphone is emerging as a new powerful tool with multiple advantages in analytical chemistry.

Objective: This project aimed to develop a simple and reliable smartphone-assisted colorimetric method to analyze Mn in steel samples.

Method: Steel samples were first dissolved in the mixture of nitric acid and phosphoric acid to convert the elemental form of Mn into Mn(II) ions. The Mn(II) ions were then oxidized into the colored permanganate ions whose color was determined via a smartphone. Quantification of Mn was performed by comparing the unknown signal with the standard calibration curve which was constructed by plotting the green value of the solution as a function of the permanganate concentration with a 2nd polynomial regression fitting. The results from the developed method were then compared with the manufacturer values and another UV/vis spectrophotometry, using the Student t-tests, to validate the method.

Results: The concentration of Mn in steel samples was determined by the smartphone-assisted colorimetry to be in the range of 0.56% to 0.97%, which had the same accuracy as the classic spectrophotometry and was in agreement with the manufacturer’s values.

Conclusion: The experimental results proved that the smartphone-assisted method is a good alternative tool for Mn analysis in steels.

Keywords: Smartphone, colorimetry, manganese, steel, permanganate, spectrophotometry.

Graphical Abstract