Digital Image Analysis for the Colorimetric Determination of Aluminum, Total Iron, Nitrite and Soluble Phosphorus in Waters

ABSTRACTA webcam was used to determine Al(III), total Fe, , and in waters by digital image colorimetry. Least squares regression was used to obtain a quadratic equation based on the red, green, blue, hue, saturation, and brightness color values, which allowed the evaluation of the wavelength of maximum absorption of the analytes. To determine the concentrations, the red, green, and blue intensities were converted into absorbances. For Al(III) and determination, the best results were attained when the absorbances relative to the green color were used. For total Fe and determination, the combined absorbances of green and blue and red and blue color led to higher sensitivity (slope) and coefficients of determination. The limits of detection for Al(III), total Fe, , and determinations were 2.59 × 10−7, 3.58 × 10−7, 1.09 × 10−7, and 1.65 × 10−7 mol L−1, respectively. The values for total Fe, , and were lower than comparative spectrophotometric techniques. The limits of detection were compatible with the Brazil...