Improved titanium method for determination of atmospheric H2O2

Gaseous H2O2 is sampled on a Ti(IV)-H2SO4 coated filter, where titanium peroxy complex is formed. After sampling the filter is leached in a phosphate buffer (pH 7) and the peroxide concentration analysed spectrophotometrically at 505 nm after having added 4-(2-pyridylazo)resorcinol (PAR). The triple complex formed shows an extinction coefficient (3.5 × 104 1 mol−1 cm−1) about 2.5 times higher than that of the [FeNCS]2+ complex, which is formed when the titanium complex is broken by addition of ferrous thiocyanate reagent. The detection limit of H2O2 for 1-h sampling can be lowered to 0.03 ppb when this new reagent is used.