Cryogen-Free Automated Gas Chromatograph System for Monitoring of Halocarbons in the Atmosphere at Background Concentration Levels

Abstract

An automated gas chromatograph/electron capture detector (GC/ECD) system is developed for the monitoring of major seven halocarbons in the atmosphere (CCl₂F₂: CFC-12, CCl₃F: CFC-11, CCl₂FCClF₂: CFC-113, CH₃CCl₃, CCl₄, CHCl=CCl₂, and CCl₂=CCl₂) at the tropospheric background concentration levels. By using two columns in series for each of two groups divided by the volatility of the compounds, the system requires neither cryogen for preconcentration nor any physical/chemical dryer for water removing. A sample amount of ca.18 ml STP is sufficient to detect these species, and analysis of sub-ambient atmospheric-pressure sample in a canister is also possible. Monitoring of these halo-carbon concentrations was carried out at 90-min intervals in the urban area.