An integrated microfluidic chip for formaldehyde analysis in Chinese herbs

• A novel integrated microfluidic chip is proposed for formaldehyde analysis.
• The validity of the proposed device is confirmed with formaldehyde concentrations ranging from 1 to 50 ppm.
• The real-world applicability is then demonstrated by measuring the formaldehyde concentration in commercial Chinese herbs.
• The measurement results deviate by no more than 3.7% from those results obtained using colorimetric method.

A novel integrated microfluidic chip with a three-layer polymethyl methacrylate (PMMA) structure is proposed for formaldehyde concentration detection applications. In the proposed device, the sample and a fluorescence derivatization reagent (Fluoral-P) are mixed in a circular mixing chamber and then flow through a serpentine reaction channel heated to a temperature of 30 °C by an integrated hotplate. Following a reaction time of 4 min, the microchip is removed from the hotplate and placed in the microscope stage of a laser-induced fluorescence (LIF) detection system. The formaldehyde concentration of the sample is then inversely derived from the measured value of the fluorescence intensity. The validity of the proposed device is confirmed by comparing the detection results obtained for standard samples with known formaldehyde concentrations ranging from 1 to 50 ppm with those obtained using a traditional UV/VIS absorption spectrometry. The real-world applicability of the proposed device is then demonstrated by measuring the formaldehyde concentration in ten commercial Chinese herbs. It is shown that the measurement results deviate by no more than 3.7% from those results obtained using colorimetric method by CAAPIC. Overall, the results presented in this study show that the proposed microchip provides a rapid and reliable tool for formaldehyde concentration measurement purposes.

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