Multifunctional microchip-based distillation apparatus II - Aerated distillation for sulfur dioxide detection.

A multifunctional microchip-based distillation apparatus is presented for the distilled of sulfur dioxide (SO2) in food products. The microchip is fabricated on poly(methyl methacrylate) (PMMA) substrates, and comprises a sample zone, a buffer zone, a serpentine distillation column, and a collection zone. In the process, the sample is introduced into the sample zone and is heated under carefully controlled temperature and time conditions. The resulting SO2 and water vapor are carried by nitrogen (N2) gas to the distillation column, where the SO2 is separated from the water vapor via the condensing effects of a continuous cold water flow. Finally, the SO2 is transported to the collection zone, where it is collected with hydrogen peroxide (H2O2) and its concentration determined using an alkali-based titration and paper-based detection method. A distillation efficiency of 90.5% is obtained under the optimal distillation conditions at concentrations of 20-4000 ppm. Moreover, a linear correlation (R2 = 0.9997) is observed between the experimental measurements of the SO2 concentration and the known concentration. The validity of the presented microchip-based distillation apparatus is further investigated by distilling the SO2 concentrations of 25 commodity samples. The detection results show that the deviation does not exceed 5.4% compared with the traditional official method.