A portable colorimetric device based on PVDF indicator gel for formaldehyde detection in food and wood products

A novel indicator gel for formaldehyde detection is described. The poly(vinylidene fluoride) polymer (PVDF) gel was used in a portable colorimetric sensor to screen for formaldehyde in food and wood products. The gel presented excellent entrapment properties based on the porous structure of PVDF. Color changes from orange to brown, green, and blue could be observed with the naked eye. Images of colorimetric products were captured using the digital camera in a mobile phone. Our sensor produced two linear ranges in the calibration curves: from 0.0 to 100 mg/L and 100 to 6000 mg/L. The limit of detection was 0.47 mg/L. Reproducibility was good. The PVDF indicator gel was stable for up to 70, and 28 days storage at 4 and 25 °C, respectively. The proposed sensor provided good accuracy with recoveries of 96.10–102.03 % for formaldehyde in real samples. The determination of formaldehyde in real samples agreed well with the reference spectrophotometric method at the 95 % confidence level. The proposed integrated colorimetric sensor provides a compact, inexpensive, portable, and semi-quantitative method of determining formaldehyde on-site.