Catalytic kinetic spectrophotometric determination of trace formaldehyde with formaldehyde-acid chrome blue K-potassium bromate system

A new kinetic spectrophotometric method for the determination of trace formaldehyde has been developed,based on the catalytic effect of trace amounts of formaldehyde on the discoloring reaction of acid chrome blue K with potassium bromate in dilute H2SO4 solution.The decrease in the absorbance has a quantitative relationship with the concertration of formaldehyde.The factor including reaction medium,concentration of reagent,temperature and time of reaction,influence of coexisting ions on the reaction are discussed.The apparent activation energy of the reaction is 1.78 kJ/mol.Under the selected conditions,the linear range of determination is 0.004 1-0.20 μg/mL and the detection limit is 4.6×10-10 g/mL for formaldehyde.The recovery is between 98%-99% and the RSD is less than 2.50%(n=5).The method has been applied to the detection of trace formaldehyde in waste water and air samples with satisfactory results.