A simple homemade colorimetric analyzer based on mobile phone for determination of nitrite in different samples

One of the trends in modern analytical chemistry is the creation of easy-to-use and universally accessible means of chemical analysis. Nowadays, image analysis based analytical procedures are becoming important because of their ability to perform fast, non-invasive and low-cost analysis on products and processes [1]. Nitrites are widely used as indicators for information about environmental pollution and for food control. The presence of high level of nitrite in drinking water can cause several diseases in human health such as methemoglobinemia and stomach cancer by the production of N-nitrosamines [2]. In this work, an image analysis procedure has been proposed using a homemade colorimetric analyzer. The proposed method is based on the direct acquisition of digital images of the sample or sample extract in a conic tube using a smart phone and a free app to convert RGB-values. For this purpose, a colorimetric analyzer with 10cm high, 15cm wide and 12cm deep was made on which a hole was embedded for inserting 15-ml Falcon polypropylene centrifuge tube with conical bottom. A white light LED lace was placed inside the box. To evaluate the performance of the homemade colorimetric analyzer, nitrite was selected as the model analyte. In order to convert nitrite to a colored product, p-nitroaniline and naphth-1-ol were used. The proposed procedure avoids the drawbacks of UV-vis spectrometric measurements caused by the restricted volume of the sample, such as reduction of the optical path or need for dilution. The proposed procedure was used successfully for determination of nitrite in different environmental samples.