Development of an analytical method using smartphones for the assessment of phenolic compounds

Abstract

Phenolic compounds exhibit antioxidant activity, which is of nutritional interest, as it has been associated with the prevention of various diseases. Therefore, the present study aimed to develop a method for quantifying these compounds in various food matrices using the mobile application PhotoMetrix UVC, a portable, fast, simple, and cost-effective colorimetric tool. Initially, an optimization of the application for the Folin-Ciocalteau method was carried out using a 24 experimental design. In the optimization, grape peel flour samples were used. Different cuvettes, the distance between the endoscope and the samples, the intensity of the image capture light, and the mode of acquisition (RGB and multiple channels) were also varied. It was possible to verify that the conditions that yielded the best results were: glass cuvette, 100 lux brightness, a distance of 0.03 cm between the endoscope and the sample, and acquisition mode in multiple channels. Samples of whiskey, coconut water, and grape seed flour were analyzed. The results were compared with the official spectrophotometric analysis method using a digital spectrophotometer. The method’s accuracy and limits of quantification and detection were calculated following EURACHEM standards. The accuracies obtained in relation to the traditional method were 93.3% for grape seed flour, 91.6% for whiskey, and 95.1% for coconut water. It was possible to conclude that the developed method showed good accuracy values. Thus, it was successfully validated, with detection and quantification limits corresponding to 7.98 mg/L and 26.61 mg/L, respectively, which are satisfactory limits since the minimum working value was 44 mg/L.