A Simple,Portable and Low Cost Device for a Colorimetric Spot-Test Quantitative Analysis

ABSTRACT

This paper describes a very simple device that can be used for colorimetric quantitative determinations, including spot-test analysis. The sensor is a light detector resistor (LDR) placed into a black PTFE cell and coupled to a low cost multimeter (Ohmmeter). The device has been tested and is easy and fast to use. Quantitative studies were performed with KMnO4 solutions and with the vanadium (V)/PAR/H₂O₂ system. Calibration curves were obtained by plotting the electric resistance of the LDR against the concentration of the colored species from 0 (blank) to 4.0 × 10^-3 mol L^-1 for permanganate and from 0 (blank) to 5.0 × 10^-5 mol L^-1 for vanadium. The detection limit (3σ) was found to be about 5.0 × 10^-5 mol L^-1 for permanganate and 4.0 × 10^-6 mol L^-1 for vanadium. The device was used to analyze total vanadium, as vanadium (V), in wastes from an adipic acid plant. The results obtained clearly show that the device can be used for accurate, precise, fast, in situ and low cost colorimetric analysis including quantitative spot-test procedures.