MEASUREMENT OF ORGANIC ATMOSPHERIC TRANSFORMATION PRODUCTS BY GAS-CHROMATOGRAPHY

The photooxidation of hydrocarbons in the atmosphere leads to the form ation of organic species which are typically more polar in character t han the parent compounds. In recent years, detailed hydrocarbon measur ements for C1 to C10 alkanes, alkenes, and aromatics in the atmosphere have involved the use of deactivated canisters and gas chromatography , similar to that described by EPA Method TO-14. However, quantitative measurements of atmospheric polar organic compounds by this method ar e unreliable. Work in this laboratory frequently involves the analysis of sample mixtures from smog chambers that are used to simulate urban atmospheres for studying the formation of ozone and other potentially hazardous compounds. Over the past several years we have developed an inert cryogenic sampling system and related GC methods for the analys is of the photochemical mixtures which are sensitive, reproducible and provide adequate separation for non-polar hydrocarbons and their pola r transformation products. These improvements have allowed a number of kinetic and mechanistic studies to be conducted, which in the past ha ve only been possible using in-situ Fourier Transform Infrared Spectro scopy. This paper describes the system development including current s trengths and limitations as applicable to experimental programs requir ing measurements of polar organic compounds at near-atmospheric concen trations.