Analysis of VOCs in Drinking Water with Headspace GC/MS Using Hydrogen Carrier Gas and a Hydrogen Optimized Source

Drinking Water
Oral Presentation

Presented by A. Willey
Prepared by B. Quimby, E. Fausett
Agilent Technologies, 2850 Centerville Rd., Wilmington, DE, 19808, United States


Contact Information: [email protected]; 302-636-3667

ABSTRACT

An Agilent 8890/5977C GC/MSD system coupled with an Agilent 8697 headspace sampler was optimized and successfully used with hydrogen carrier gas for the analysis of volatile organic compounds (VOCs) in drinking water. Recent concerns with the price and availability of helium have led laboratories to look for alternative carrier gases for their GC/MS methods. For GC/MS, hydrogen is the best alternative to helium, and offers potential advantages in terms of chromatographic speed and resolution. However, 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, peak tailing, and nonlinear calibration for some analytes. Therefore, a new EI source for GC/MS and GC/MS/MS was developed and optimized for use with hydrogen carrier gas. The new source, named HydroInert, was used in the system evaluated here. In addition to the HydroInert source, the chromatographic conditions were optimized to provide separation of 80 volatile compounds in seven minutes. Standards and samples were analyzed in both scan and SIM data acquisition modes. For the scan data, spectra were deconvoluted with MassHunter Unknowns Analysis software and searched against NIST 20 to assess the spectral fidelity resulting in an average library match score of 94. In both modes, quantitative calibration was performed for the 80 compounds over the range of 0.05 µg/L to 25 µg/L. The measured method detection limits (MDLs) were in the ppt range. This presentation demonstrates that with optimization, hydrogen carrier gas can give excellent results for the analysis of VOCs in drinking water.