An environmentally friendly analytical approach based on spot test and digital image to evaluate the conformity of bleaching products

摘要

A new, simple, and low residue analytical method is proposed to check the conformity of bleach products containing hypochlorite. The method is economical and environmentally friendly because it uses low cost materials based on natural indicators and generates only 600 μL of waste per test and it allows 12 analyses within 5 min using only one digital image. The method consists of capturing a digital image of the hypochlorite colorimetric reaction with anthocyanins using a smartphone and a system built with low cost materials to optimize the acquisition of data. Under optimized reaction conditions, the analytical curve was linear in a hypochlorite concentration range of 1.23 × 10~(-4) to 3.69 × 10~(-4) mol L~(- 1), with limits of detection and quantification of 3.5 × 10-5 mol L~(- 1) and 1.16 × 10~(-4) mol L~(- 1), respectively. The obtained results are in agreement with those obtained using the titrimetric method recommended by the American Society for Testing and Materials (ASTM) with a confidence level of 95%. Moreover, the method provided 100 times lower residue per analysis than that obtained by iodometric titration, and it does not present toxicity when compared to other methods reported in the literature.