Avaliação da colorimetria por imagens digitais empregando smartphones para determinação da dureza em águas

Abstract

This work aims to develop and evaluate a method for quantification of hardness in water by colorimetric digital imaging using smartphones. Hardness is a physical-chemical property of water that expresses the concentration of dissolved calcium carbonate and magnesium carbonate, which, although not harmful to health, can cause damage in industrial systems and cleaning processes. The official method, complexation volumetry, involves the use of large volumes of samples and reagents and is time consuming. The proposed method aims to be more practical and accessible, besides being low cost and possible to use at the collection site. The procedure involves collecting the sample, adding buffer and indicator, capturing an image of the sample using a smartphone, and then determining the color presented by this sample. First the process was optimized to find the best reagent concentration, then a calibration curve was drawn, and finally validation of the method against the official method. The results obtained indicated that the proposed method is valid and feasible, but presented a low response range due to the indicator used and high percentage error due to the sensibility of the capture process.