A fully integrated 3D printed platform for sulfite determination in beverages via gas diffusion membrane extraction and digital video treatment

In this study, we have described a miniaturized, simple, and low-cost device for sulfite determination in beverages by coupling Gas Diffusion Microextraction to paper-based analytical devices. The color change of an acid-base indicator - promoted by the generated gaseous SO₂ - impregnated onto the paper surface was monitored in the function of time by video recording using a smartphone. The analytical information was related to the Hue, Saturation, Value (HSV) color space extracted from the video file. The complete analytical platform was built using a 3D printer, allowing the easy fabrication of a low-cost tailored device. Under optimized conditions, a linear relation from 5 to 90 mg L^-1 was obtained using 30 µL of the reagent, 1 mL of sample, and 10 min of analysis. The relative standard deviation and the limit of detection were 2.2 % and 1.6 mg L^-1, respectively. The method was successfully employed in several beverages, such as juices, soda, and coconut water.