Recent concerns with the price and availability of helium have led laboratories to look for alternative carrier gases for their GC/MS and GC/MS/MS systems. For GC/MS, hydrogen is the best alternative to helium. Among the problems encountered when converting to hydrogen carrier gas in GC/MS is that hydrogen is not an inert gas and may cause chemical reactions in the mass spectrometer electron ionization (EI) source. This can lead to disturbed ion ratios in the mass spectrum, spectral infidelity, and peak tailing. Therefore, a novel EI source for GC/MS and GC/MS/MS was developed and optimized for use with hydrogen carrier gas.
To evaluate the novel EI source performance, several classes of compounds including SVOCs, VOCs, PAHs, PCBs, phthalates, and pesticides were analyzed with GC/MS and GC/MS/MS using hydrogen as the carrier gas. The results demonstrated:
- Good spectral fidelity for compounds susceptible to hydrogenation in the source resulting in higher library match scores observed against the NIST spectral library when compared to the conventional EI source. This effect was especially pronounced for nitrobenzene and other nitro-compounds
- Excellent chromatographic peak shape, especially for late-eluting PAHs with a fast analysis method that is known to amplify any chromatographic peak tailing
- Good performance for the analysis of over 200 pesticides with both GC/MS and GC/MS/MS
- Dramatically improved calibration performance for SVOCs
- Excellent spectral matching and calibration performance for VOCs analyzed with headspace in drinking water
- Demonstrated excellent sensitivity at the sub-ppb level for many analytes including PAHs and PCBs, exceeding that typically seen with hydrogen carrier gas with both GC/MS and GC/MS/MS
- Stable system performance for over 5,000 injections of a heavy soil extract.
The novel EI source addresses one of the operational issues impacting the environmental laboratory industry with using hydrogen as the carrier gas.
Anastasia A. Andrianova
GC/MS Application Scientist
Agilent Technologies, Inc.
Anastasia Andrianova is a GC/MS Applications Scientist in the Mass Spectrometry Division of Agilent Technologies, located in Wilmington, Delaware. She received a Ph.D. in analytical chemistry from the University of North Dakota (Grand Forks) in 2017 and a combined masters’ and bachelor’s degree in analytical chemistry from the Moscow State University (Moscow, Russia) in 2014. Anastasia has been at Agilent Technologies since 2018. She has authored or co-authored over 30 journal articles and application notes, as well as 1 patent in the field of analytical chemistry, focusing on chromatography and mass spectrometry. Anastasia is currently working in GC/MS applications in multiple areas with a focus on food and environmental analysis.