Determinação de cloreto em águas por imagens digitais

Abstract

Chloride is one of the parameters used in checking the quality of water, chloride ions can be found in waters from mineral deposits and from polluted sources such as sewage and industrial waste. The chloride (Cl-) anion can be determined by gravimetric, volumetric, potentiometric and colorimetric methods. However, for substances that form colored compounds, the measurement of the intensity of the formed color allows to determine the amount of analyte in the sample. Thus, digital images can be used for the quantitative determination of an analyte in the sample, that is, it allows the determination of the chlorine content. In this work, a titration based on digital images obtained by webcam was used to determine the chloride content in tubular wells for water supply in the municipality of Itacoatiara-AM. In order to determine the chloride content by the proposed method, the acquired samples were submitted to a Classical titration based on digital images with webcam capture, with each addition of titrant (AgNO3). Then all images were processed using ImageJ software, being converted into numerical values proportional to each channel of the RGB color system used to obtain the norm, � = √�2 + �2 + �2 . The values obtained by the standard were used in the construction of the titration curve as a function of titrant volume. According to the paired t-test, there are no statistically significant differences in the 95% confidence interval between the two methodologies. The relative standard deviations were less than 5%, being within the stipulated standard. Therefore, the proposed method proved to be reliable for determining the chloride content.