Poster Presentations
Day 2, June 11（Thu.） Room P (5F 501+502)
- 2P-31
Ethylene-doped nitrogen carrier gas enables sensitivity enhancement while preserving EI-like spectra in GC–MS
(Kyoto Inst. Tech.)
oYasuro Fuse, Xue Chu
Helium scarcity is accelerating the shift to nitrogen carrier gas in GC–MS; however, conventional EI in N₂ often causes severe sensitivity loss and poorer library matching. This work establishes a helium-free, EI-compatible workflow by combining ethylene-assisted sensitivity recovery with systematic method optimization. Introducing trace ethylene into an N₂ carrier stream restores and tunably enhances ionization efficiency while preserving EI-like fragmentation for representative semi-volatile organics, including PAHs and phthalates. By varying pressure, flow rate, and dopant fraction, we identify an operating regime where collision-assisted energy relay becomes dominant. In this regime, N₂-derived primary ions and excited species transfer energy and/or charge to ethylene, producing longer-lived intermediates that efficiently ionize analytes without changing spectral fingerprints. Performance is evaluated using signal-to-noise ratio, detection limits, and a practical “energy relay efficiency” metric. Incorporating rarefaction (Knudsen number) considerations, we define operating windows that balance electron transmission and collisional activation. The approach requires no major hardware changes beyond a controlled dopant inlet and is compatible with routine quadrupole GC–MS platforms.