Catalytic kinetic spectrophotometric determination of trace formaldehyde with formaldehyde-evans blue-potassium bromate system

A new kinetic spectrophotometric method for the determination of trace formaldehyde has been developed, based on the catalytic effect of trace amount of formaldehyde on the discoloring oxidation reaction between potassium bromate and evans blue in dilute H3PO4 medium. The decrease in the absorbance has a quantitative relationship with the concentration of formaldehyde. The influence of reaction medium, concentration of reagent, reaction temperature and time, and coexisting ions on the reaction were discussed. Under the selected conditions, the linear range of determination is 0.015-0.30 μg/mL and the detection limit is 8.6 × 10-8 g/mL. The method has been applied to the determination of trace formaldehyde in waste water and air samples with the recovery of 99%-102% and the RSD of less than 2.50% (n = 6). The results are in good agreement with those obtained by MBTH method.