Determination of Formaldehyde Based on the Fading Reaction of Methyl Orange by Reversed Flow Injection Spectrophotometry

A rapid method for determination of formaldehyde in paint and indoor air by flow injection spectrophotometry based on the catalytic effects of formaldehyde on the oxidation reaction of methyl orange by potassium bromate in sulfuric acid medium was established. The relationship of the reduced absorbency to the concentration of formaldehyde was good linearity and the maximum absorption peak located at 508 nm. The affecting factors on the strength of absorption including temperature, acidity, dosage, coexisting ions and so on, and the optimal conditions of the reaction in the system were investigated. Calibration graphs were linear for ranges of 0 to 1.0 mg/L and a detection limit of 1.1×10-8 g/mL formaldehyde was achieved. The proposed method was successfully applied to the analyses of paint and indoor air samples, with relative standard deviation of less than 1.8% and the recoveries are 94.6％ to 106.2％for the determination of formaldehyde.