Development of a low-cost colorimeter and its application for determination of environmental pollutants

Herein, a novel colorimeter based on the Beer-Lambert law was designed for detection of environmental pollutants in water with a high precision, simple, and miniaturized device using a tetracycline-Eu³⁺ complex, cadmium reduction, diazotization, 1,10-phenanthroline, and periodate oxidation. The newly developed colorimeter could detect many environmental pollutants including tetracycline, nitrate, nitrite, Fe, and Mn, which were used to evaluate its performance. Simultaneously, a modified algorithm was applied to extend the linear response range. The colorimeter was comprised of an Red Green Blue Light Emitting Diode (RGB LED) light, focusing len, 3D printed stand for the cuvette, and light-sensitive photodiode detector. Microcontroller Arduino Uno processing technology was used to form a stable integrated structure. With the use of a novel algorithm, the device exhibited a wide linear response, ranging from 0-20, 0-17, 0-0.3, 0-1.75, and 0-15 mg/L for tetracycline, N-NO₃^-, N-NO₂^-, Fe, and Mn, respectively, and low limits of detection (0.88, 0.34, 0.031, 0.08, and 0.47 mg/L for tetracycline, N-NO₃^-, N-NO₂^-, Fe, and Mn, respectively). The advantages of high precision and low cost allow the novel design to be used for the detection of environmental pollutants.