Fabrication of an Automatic Analyzer Based on an Integrated Gas Diffusion System and Optical Sensor for the Determination of Sulfite in Beverages and Dried Fruits

Abstract

Sulfite compounds are frequently utilized as antibacterial agents in the production of foods and beverages; however, they have the potential to cause allergic reactions in some individuals. In this work, a miniaturized automatic analyzer based on the integration of a microflow gas diffusion unit (GDU) with an optical sensor was developed. The GDU was microfabricated from polymethyl methacrylate (PMMA). In the donor stream of GDU, sulfite was reacted with HCl to produce sulfur dioxide gas (SO₂), which was then diffused through a PTFE hydrophobic membrane into a receiver segment holding Fe(III) and the colorimetric agent (1,10-phenanthroline). The released SO₂ gas reduced Fe(III) to Fe(II) and the resulting Fe(II)-phenanthroline complex was optically detected by a laboratory-made optical sensor. The automated system permitted the evaluation of sulfite amount in mg L^-1 (SO₂). The nonlinear calibration graph was obtained in the range of 1.0-35.0 mg L^-1 (R² = 0.9991) with the limit of detection (3) down to 0.3 mg L^-1. The developed system offers greater levels of automation and user-friendliness and demonstrates adequate applicability for the determination of sulfite in fruit and beverage drinks samples from a local market of Thailand.