Automated measurement system for H2O2 in the atmosphere by diffusion scrubber sampling and HPLC analysis of Ti(iv)–PAR–H2O2 complex

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Abstract
An automated selective measurement system for monitoring hydrogen peroxide (H2O2) in the atmosphere was developed (using a diffusion scrubber coupled to a high performance liquid chromatograph) due to the importance of H2O2 in understanding tropospheric chemistry and its harmful effects on vegetation. H2O2 in the atmosphere was effectively collected by a diffusion scrubber, which consisted of a hydrophobic porous polytetrafluoroethylene (PTFE) tube positioned concentrically within a Pyrex glass tube. Titanium(IV)–4-(2-pyridylazo)resorcinol (Ti(IV)–PAR) solution acidified at pH 2.2 was used as the scrubbing solution for the diffusion scrubber. After the collection of the air sample by the diffusion scrubber, the pH value of the Ti(IV)–PAR scrubbing solution was adjusted to pH 11.9 to form a stable complex of Ti(IV)–PAR–H2O2. An aliquot of the sample solution was injected into a high performance liquid chromatograph equipped with a semi-micro-reversed-phase column and a spectrophotometric detector set at 508 nm for separating and determining the Ti(IV)–PAR–H2O2 complex. The automated measurement could be performed at 60 min intervals. The collection efficiency of H2O2 was higher than 98% at an air flow rate of 1.0 l min−1. The detection limit (3σ of the blank value) of H2O2 was 9 parts per trillion by volume (pptv) for an air sampling volume of 55 l. The interference from coexisting O3 or SO2 in the atmosphere was negligible during the collection of H2O2 by the diffusion scrubber. The developed automated measurement system was suitable for monitoring H2O2 in the atmosphere.