Rapid integrated microfluidic paper-based system for sulfur dioxide detection

An integrated platform consisting of a microfluidic paper-based/PMMA (Polymethyl-Methacrylate) chip and a small battery-operated detection system is proposed for the concentration detection of sulfur dioxide (SO 2 ). In the proposed method, a small strip of filter paper is coated with acid-base indicator and then inserted into a PMMA microchip. The SO 2 sample is then injected into the reservoir of the chip; prompting a reaction with the acid-base indicator. The chip is transferred to the detection system, where the reaction-induced color change is captured by a CMOS (Complementary Metal-Oxide Semiconductor) camera. Finally, the CMOS image is transferred to a cell phone via a USB (Universal Serial Bus) connector and the SO 2 concentration is derived using self-written RGB color analysis software. The experimental results obtained for 10 control samples show that the correlation coefficient for the variation of the R(ed) signal intensity with the SO 2 concentration is equal to R 2 = 0.9971 in the low-concentration range (20 ∼ 600 ppm) and R 2 = 0.9920 in the high-concentration range (600 ∼ 5000 ppm). The real-world applicability of the proposed platform is demonstrated by measuring the SO 2 concentrations of fifteen commercial food samples. The concentration measurements deviate by no more than 4.29% from those obtained using a standard macroscale technique. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based system provides a cheap, compact and reliable method for SO 2 concentration measurement purposes.