Publications in Scientific Journals:

J. Laimer, G. Misslinger, H. Störi:
"Limitations in the time resolution of quadrupole mass spectrometry using a flushed extraction probe ";
International Journal of Mass Spectrometry, 223-224 (2003), 301 - 312.

English abstract:
At gas pressures higher than approximately 5 mbar it is common practice to use a two-stage pressure reduction set-up to accomplish the needed transition down to the operating pressure of a quadrupole mass spectrometer (QMS). We have demonstrated that, by using a specially constructed helium flushed probe system, a quick transport of species extracted from a process gas to a QMS can be achieved. An experimental investigation using a very fast chemical decomposition process revealed a delay of the signal of more than 50 ms, but a time resolution of only a few milliseconds for this set-up. The broadening of the signal can be explained and described by a combined effect of diffusion during the transport of the species within the probe system and the mean residence time of the species in the ionisation chamber of the QMS. An investigation of the contributions of different effects on the limited time resolution revealed that the present set-up is close to the experimentally possible limits of this technique. However, as an instrument function describing the measurement system was derived with good accuracy, a deconvolution of measurements with the instrument function would allow a time resolution down to 2 ms.

Keywords: Mass spectrometry; Gas sampling probe; Time resolution

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