Smartphone-based miniaturized, green and rapid methods for the colorimetric determination of sugar in soft drinks

Total sugar content of soft drinks was determined in a 3D-printed chamber equipped with an USB camera attached to the smartphone to take pictures directly from the vessels used for the reaction of monosaccharides with cupric ion from Benedict's reagent. The freely available PhotoMetrix UVC application was used to control the device and process images. Reaction time, total volume of solution and illumination were evaluated. Images were captured before and after centrifugation and the results were compared with official method (AOAC 923.09, Lane-Eynon titration). Partial least squares calibration was used reaching suitable values (R2 above 0.99; Root mean square error of calibration (RMSEC) and Root mean square error in cross-validation (RMSECV) values lower than 0.07 and 0.23 mg mL−1, respectively). The proposed methods presented agreements from 95.3 to 108.7% to the official one. Hundreds of samples can be analyzed in one hour and reductions in energy expenditure by 5.5 times and waste volume by 78 times were obtained in relation to the AOAC method.