The use of a hollow cathode glow discharge (HCGD) as an atomic emission spectrometric element specific detector for chlorine and bromine in gas chromatography

The use of a dc hollow cathode glow discharge (HCGD) as an element specific detector for chlorinated and brominated hydrocarbons was investigated. An interface was constructed which allows the coupling of a gas chromatograph with a demountable HCGD using metal (Cu, Al, Mg) or graphite cathodes, helium as the working gas (pressure 0.8 kPa) and currents of about 30-60 mA at preset voltages ranging from 350 to 1000 V. In order to obtain optimum conditions for the determination of halogenated hydrocarbons, the influence of the dimensions and the materials of the cathode on the signals for the Cl and Br lines in the visible region was evaluated. After optimising the plasma parameters with the Cl II 479.454 nm and Br II 478.550 nm atomic emission lines, detection limits of 3 pg s(-1) for chlorine and 5 pg s(-1) for bromine were obtained, which depended on dilution of the working gas with the organohalogen compounds. The linear dynamic ranges were found to extend from 50 to 1500 pg s(-1) for Cl and from 100 to 3500 pg s(-1) for Br. The detection of 1-bromo-3-chloropropane, 1-bromo-2-chloroethane and dichloromethane at the low pg s(-1) level was possible.