CONTINUOUS DETERMINATION OF GASEOUS FORMALDEHYDE BY A CHEMILUMINESCENCE METHOD

A continuous flow method for the determination of formaldehyde in urba n air has been developed based on the chemiluminescence reaction betwe en hydrogen peroxide solution and gaseous formaldehyde in the presence of 3,4,5-trihydroxybenzonic acid (gallic acid) in alkaline solution. The emission produced by the chemiluminescence reaction is proportiona te to the formaldehyde concentration from 10 ppb (10(9)) v/v to 50 ppm v/v. The limit of detection [signal-to-noise (SM) = 3] for gaseous fo rmaldehyde is 10 ppb. The relative standard deviation for six measurem ents of 25 ppb v/v of formaldehyde is 7.1%. Hydrocarbon, sulfur dioxid e, carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, oz one, acrolein and benzaldehyde do not interfere; however, propinaldehy de and acetaldehyde interfere slightly. Generally, the concentrations of propinaldehyde and acetaldehyde in urban air are less than formalde hyde, therefore their interferences can de considered negligible.