Determination of trace amounts of formaldehyde by ion-exchange resin thin-layer spectrophotometry

Abstract

A simple but highly sensitive method has been developed for the determination of trace amounts of formaldehyde. The method proceeds as follows: (1) formaldehyde is reacted in alkaline media with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole; (2) the reaction product is oxidised with potassium periodate to a reddish purple complex; (3) the complex is concentrated and fixed on a finely divided anion-exchange resin using the batch method; (4) the resin is mixed with a finely divided cation-exchange resin and the mixed resins are filtered, leaving on the membrane filter a coloured thin-layer disc, 17 mm in diameter and about 0.2 mm thick; (5) the absorbance of this thin layer is measured directly with a spectrophotometer. The method was applied to the determination of formaldehyde in an air sample.