ATMOSPHERIC PEROXY RADICAL MEASUREMENTS BY ION-MOLECULE REACTION MASS-SPECTROMETRY - A NOVEL ANALYTICAL METHOD USING AMPLIFYING CHEMICAL CONVERSION TO SULFURIC-ACID

A novel method for measuring atmospheric peroxy radical concentrations has been developed and tested in various field and laboratory studies . The method relies on amplifying chemical conversion of peroxy radica ls to gaseous sulfuric acid via the chain reaction with NO and SO2 (NO /SO2 chemical amplifier) and detection of the reaction product sulfuri c acid by ion molecule reaction-mass spectrometry (IMR-MS). The high s ensitivity of LMR-MS and the low atmospheric background of gaseous H2S O4 allows for work with small chain lengths and short reaction times, which reduces the impact of potential interference and loss processes. The basic kinetic foundations of the amplification process including its sensitivity to interference and radical loss processes are discuss ed. Field and laboratory measurements indicate nominal operation of th e NO/SO2 chemical amplifier system and its suitability for highly sens itive peroxy radical measurements even under atmospheric conditions ch aracterized by low peroxy radical concentrations such as nighttime, wi nter, and high-latitude conditions.