Kinetic spectrophotometric determination of trace formaldehyde on the oxidation of ethyl orange with potassium bromate

A kinetic spectrophotometric method for the determination of trace formaldehyde was proposed, which is based on the kinetic effect of formaldehyde on the discoloring reaction of ethyl orange oxidized by potassium bromate in the dilute sulfuric acid solution. Under the optimum conditions, the decrease in absorbance was measured at 507 nm at a fixed time interval, and the linear range for formaldehyde is 0～0.24 mg/L with a detection limit of 0.004 mg/L. The method was applied to the determination of trace formaldehyde in drink and waste water and air samples with satisfactory results of RSD less than 3%(n=6) and recovery of 102%.