Comparison of gas chromatography detection limits and relative responses of common alternative fluorocarbons using electron capture, atomic emission, and mass spectrometry detection

Abstract

Detection limits for several common alternative fluorocarbons (AFCs) using electron capture detector (ECD), mass spectrometry (MS) and atomic emission detector (AED) gas chromatography (GC) are determined and compared. Mass detection limits for chlorofluorocarbon (CFC) CFC-12, and hydrochlorofluorocarbons (HCFCs) HCFC-22, HCFC-123 and HCFC-124 are found to be in the picogram range. Those of hydrofluorocarbons (HFCs) HFC-125, HFC-134a and HFC-152a are found to be in nanograms using ECD and in the picogram range for the MS and AED. HFC-152a was not detected by the ECD. Relative ECD responses for all AFCs are at least one order of magnitude lower than that for CFC-12. The relative MS responses are found to be in the same order of magnitude of that for CFC-12. For the AED, all AFCs had somewhat higher responses than CFC-12 with the exception of HFC-152a, which showed the same response than CFC-12. The mass detection limits for 1 L sample with a signal-to-noise of 3 σ is in the low ppt (v/v) for AED and MS. ECD has a limit of detection of about one order of magnitude higher than other detectors for the HCFCs, and a limit of detection in the nanogram range for the HFCs. MS has slightly higher sensitivity than the AED, and both detector proved to be far better for the detection of the AFCs than the ECD. Preconcentration of whole-air sample is required for all tested methods to make measurements at predicted levels. An amount of 1–10 L samples are needed for AED and MS while ECD requires 10–100 L samples for HCFCs and over 100 L for the HFCs. A more sensitive detector is still needed to perform in situ analysis without preconcentration for the current atmospheric concentrations.