High-speed mass spectrometric detector for gas chromatography

Method TO-14 is the EPA protocol for sampling and analysis of 41 ambient VOCs. It is based on the collection of whole air samples in Summa-polished canisters. Analysis is done by gas chromatographic separation with multiple specific detectors or mass selective detection. Typical run times exceed 25 minutes. As a result, limited numbers of samples can be run in a day, and field studies often lead to large backlogs of samples which have to be stored for extended periods of time before they can be analyzed. Faster sample throughput, could be attained with high-speed gas chromatography using narrow-bandwidth injections (100 ms or less) and high carrier gas velocities. However, detector response times are generally too slow to characterize such narrow peaks adequately. Specially designed electrometers are required to operate at high speed while distinguishing data from electrical noise. Mass spectrometers are ideal gas chromatographic detectors because they are universal (detect everything) and specific (distinguish one co-eluting compound from another). However, typical mass spectrometer scan rates ({approximately}3/sec) are too slow for optimal function, even with conventional capillary chromatography. The Leco FCD-1000 TOF Mass Spectrometer can function as a high-speed gas chromatograph detector of adequate sensitivity. Rapid data acquisition permits characterization ofmore » extremely narrow GC peaks. Mass spectral bias is eliminated because all ions in each mass spectrum depart the ion source simultaneously. Peak deconvolution can be used to resolve analytes which are not separated chromatographically. The instrument can cope with up to 5 mL/min carrier flow, and could replace most GC detectors. 7 figs.« less