An integrated platform consisting of a microfluidic paper-based analytical device (μPAD) and a portable detection system is proposed for low concentration formaldehyde (CH2O) detection. In the proposed approach, the reaction zone of the μPAD is coated with ammonium acetate (AA) and acetoacetanilide (AAA) indicator and is dried at 40 °C for 30 min. The formaldehyde sample is then dripped on the reaction zone and the μPAD is transferred to a hot plate in the portable detection system. A Hantzsch reaction is induced by heating the μPAD at 30 °C for 10 min. The resulting fluorescent formaldehyde-Acetoacetanilide complex (dihydropyridine derivative) is observed by a CMOS camera and the color image is transferred to a smartphone by means of a connector. Finally, the CH2O concentration is derived using self-written RGB color analysis mobile software implemented on the phone. The experimental results obtained using control samples with known CH2O concentrations in the range of 0.2–2.5 ppm show that the B (blue) fluorescence intensity (Y) and formaldehyde concentration (X) are related as Y = 29.455 X + 117.64. Moreover, the correlation coefficient is equal to R2 = 0.9937. The real-world applicability of the proposed detection platform is demonstrated by measuring the CH2O concentration in twelve commercial food samples. It is shown that the concentration measurements obtained using the proposed system deviate by no more than 6.2% from those obtained using a conventional spectrophotometric technique. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based system provides a compact and reliable tool for low concentration CH2O measurement purposes.
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