A method is described for the spectrophotometric determination of atmospheric H2O2at the ppb level. H2O2reacts with pyridine-2,6-dicarboxylic acid and vanadate(V) in acidic solutions forming the stable orange-red coloured oxo-peroxo-pyridine-2,6-dicarboxylato-vanadate(V) chelate. The fairly intense light absorption of this complex at 432 nm is widely unaffected by other atmospheric constituents such as NOx, SO2,O3, aldehydes, HCs and metal ions. No changes occurred with variation in pH or reagent concentrations over a wide range. The complex is formed very fast and remains stable for at least several hours. Sampling of atmospheric H2O2is carried out in either a discontinuous manual or a continuous automatic manner. Particular sampling devices have been developed ensuring quantitative absorption of H2O2over wide ranges of H2O2concentration and of sample air flow rate. From preliminary experiments the detection limit has been derived to be about 1 ppbv H2O2. The performance characteristics of the method have been determined with the aid of test atmospheres. For the preparation of the test atmospheres two methods were developed. © 1987.
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