A simple device for quantitative colorimetric diffuse reflectance measurements

A very simple and low cost reflectometer, for colorimetric diffuse reflectance measurements is described. The proposed instrument uses a light dependent resistor (LDR), as a sensor, and a light emitter diode (LED), as light source. The performance of the device was compared with that of a commercial instrument, measuring the reflectance of the Pantone® Process Black Uncoated Palette. The quantitative analysis of nickel, in a catalyst, using dimethylglyoxime as colorimetric reagent, was also used to test the device. The observed precision was about 6% (R.S.D.). These results were compared with those obtained by the gravimetric method using the same reaction, through the statistical Student’s t-test procedure. A complete agreement was observed. The good quality of all the obtained results allows the recommendation of the instrument for diffuse reflectance measurements including quantitative analytical procedures.