Spectrophotometric determination of hydrogen peroxide in rainwater

Hydrogen peroxide in rainwater has been determined from the measurement of absorption at 432 nm after the formation of the stable oxo-peroxo-pyridine-2,6-dicarboxylatovanadate(V) complex (OPDV) in acid media. Determinations were in good agreement with those using a modified p-hydroxyphenylacetic acid (PHPA) emission method. The linear range for the OPDV method is from 0.05 to 50 ppm H 2O 2, and the limit of detection under the analytical conditions employed was 5.8 nmol H 2O 2 for a 20 cm 3 rainwater sample. The volume weighted mean H 2O 2 concentration in rainwater collected at roof-top level in central Kowloon was 15.9 μM ( N=10), and the ratio of non-sea salt sulphate and H 2O 2 concentrations was significantly correlated with pH. The OPDV absorption method was also employed for the determination of ambient gaseous H 2O 2, and liquid-nitrogen cold-trap collection gave results about 30% lower than impinger sampling, where artifact H 2O 2 formation occurred.