Determination of Formaldehyde in Air by Iodine Fading Spectrophotometry

A new spectrophotometric method for the determination of formaldehyde was proposed. It was based on the reaction of formaldehyde and excessive potassium bichromate in sulfuric acid medium. After the reaction,surplus potassium bichromate reacted with potassium iodide and iodine was formed. It had the maximum absorbance at 350nm. The optimum experimental conditions for the determination were studied. Beer's law was obeyed between the concentration of formaldehyde 0.225 to 1.575μg/mL and the decrease of the absorbance. The determined regressive equation was A350=0.005+0.248ρ(μg/mL),and the related coefficient r was 0.999. The method was applied to determine free formaldehyde in the air,and the RSD was between 1.28% and 1.67%.