Paper-based devices for formaldehyde analysis

Abstract

A rapid and simple paper-based analytical device (PAD) for quantitative analysis of formaldehyde in food samples has been developed. The analysis was based on sulfite assay where the formaldehyde (FA) was reacted with excess amount of sulfite to generate sodium hydroxide and the product consequently quantified using acid-based titration on the PAD. The acid-based titration PAD consisted of a central sample zone connected to ten reaction and detection zones. Polyethylene glycol and phenolphthalein (indicator) were deposited to the detection zones, and different amounts of titrant, potassium hydrogen phthalate (KHP), were added to the reaction zones. The formaldehyde concentration can be quantified from the number of colorchanged detection zone(s) which are correlated to known amount of KHP on reaction zone. The areas of each zone and volumes of the reagents added to the corresponding zones were optimized. The PAD gave range of FA analysis from 100 to 1000 ppm and the LOD was 100 ppm. The PADs were stable for up to a month under dark and cold conditions. The analysis of formaldehyde in food samples was demonstrated using the PAD can be completed within 5 minutes, and the results agreed well with those obtained from the classical titration.