Determination of ultra-trace amount of halo-hydrocarbon in nitrogen by atmospheric pressure ionization mass spectrometry

The monitoring of halo hydrocarbons such as R134a in atmosphere has attract great attention due to its strong global warming effect. In this study, on-line atmospheric pressure ionization (API) and electron impact ionization (EI) mass spectroscopy was used to measure R134a at ambient level (ppt, 10(-12) mol/mol). A dilution system was developed to test the linearity of API/EI MS. Results showed that the sensitivity of API MS was much higher than that of EI MS. A good linearity could be obtained at the range of 10-75 ppt for API MS. The API MS could directly measure R134a at ambient level without preconcentration devices.