Influence Factor of Test Formaldehyde in Air by Iodine-Starch Spectrophotometry

A new spectrophotometric method for the determination of formaldehyde was proposed.The method 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.Then starch was added and a blue complex was formed,which had the maximum absorbance at 596nm.The optimum experimental conditions for the determination were studied.Beer's law was obeyed between concentration of formaldehyde(0.225—7.875μg/mL) and the decrease of the absorbance.The regressive equation was A596=0.1476C(μg/mL)+0.00199,the relative coefficient was 0.9994 and e=4.428×103L·mol-1·cm-1.The method was applied to determine free formaldehyde in the air.A comparison was done between the proposed method and the acetyl acetone spectrophotometry.The results obtained from the two methods show no obvious difference.