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

Abstract

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.

Keywords: Aerated distillation; Alkali-based titration; Microchip; Paper-based; Sulfur dioxide.