Colorimetric Paper Indicator Associated with Smarthphone for Formaldehyde Detection in Milk Based and Personal Care Products

Due to its low cost, formaldehyde was used as conservative in hygienic and cosmetic products. However, formaldehyde is strongly reactive and toxic, so its use has been forbidden in several products. Recently, formaldehyde has been illegally added in milk, causing innumerous health problems. In this work we developed a colorimetric paper indicator based on Schiff’s reagent, which can be associated with a smartphone application. The paper stabilizes the Schiff’s reagent, avoiding its decomposition during short periods. The natural color of the paper indicator remains after the treatment with Schiff’s reagent. The tests consist in apply a small amount of the test sample in the paper treated with Schiff’s reagent, so that a new color will show up. If pink appears, the presence of formaldehyde is considered negative, whereas if the color purple shows the presence of formaldehyde in the sample can be considered positive. A smartphone application was developed to help people with difficulties or inability to distinguish those colors. The paper indicator successfully detected the presence of formaldehyde in commercial products such as detergents, shampoos and conditioners. Regarding milk-based products, the paper indicator is especially sensitive to detect formaldehyde, clearly identifying concentrations of 0.01% (v/v), as shown in Figure 1. The paper indicator has low cost and can help the supervision of milk and other products, as a trial test in regulatory agencies or for home consumers.