Digital-imaging colorimetry of reaction between formaldehyde and purpald reagent on paper-based analytical device
Digital-image colorimetry has been used for the determination of formaldehyde using purpald reaction on a simply fabricated paper-based analytical device (PAD). The PAD can be simply fabricated by cutting filter paper to small piece (6 mm diameter) using a puncher. The reaction between formaldehyde and purpald reagent was performed and generated the purple product on the PAD. A photograph of the resulting PAD, placed in a home-made mini-studio box, was taken by a smart phone’s camera with the fixed camera settings: ISO value, white balance and shutter speed. The photograph then was analyzed the color intensity by ImageJ computer software. Using 5.0 μL of purpald reagent and the reaction time of 720 s, the standard calibration graph was in linear-log model at the range of 1.0-20 mg L-1 formaldehyde with R2 of 0.9919. This method will be an alternative method which is simple and low-cost for the formaldehyde determination.
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