dc.description.abstract
It is more than 50 years ago that Giddings described the concept of low pressure- or vacuum outlet-gas chromatography (LP- or VO-GC) [1]. Nevertheless, it should take almost 30 years until the theoretical potential of this technique was also transferred into practice [2].
For vacuum outlet GC, short, wide bore capillary columns are typically used (e.g. 5-10 m long, 0.53 mm ID) that are operated under vacuum conditions [3]. This is normally achieved by the coupling to a mass spectrometer as a detector. To limit the flow to the mass spectrometer to an acceptable value, a restriction is used that often consists of a short piece of a narrow inner diameter capillary column which at the same time may serve as a guard column [4]. Under these conditions, the vacuum extends almost throughout the entire analytical column and, as a consequence of the reduced density and viscosity of the mobile phase, mass transfer is significantly enhanced. This allows for a much faster chromatography than under normal pressure conditions, although separation efficiency is compromised due to the short columns used. This latter disadvantage is mostly compensated by the use of the MS as a selective detector [5].
In addition to speed of separation, higher sample throughput, lower detection limits, less analyte degradation, reduced peak tailing, increased sample capacity, and greater ruggedness are often claimed as further advantages of this technique.
It is evident that these advantages are more important with semi- and less volatile organic compounds, and thus the majority of applications so far have come from the analysis of semi-volatile organic compounds. The critical evaluation of the practical implementation of this technique will highlight its advantages and also discuss its shortcomings which become particularly evident as very volatile analytes are analysed. The LP-GC/MS technique is compared and contrasted with other chromatographic techniques that allow for fast separations. The individual merits and shortcomings of each technique are compared, making eventually clear that there is no single technique that combines all desirable features of chromatography, and that certain trade-offs must be made when the focus is on fast chromatography. However, vacuum outlet-GC/MS indeed combines many attractive features and is thus a most suitable method for achieving fast chromatographic separations.
Keywords: fast chromatography, gas chromatography, mass spectrometry, trace analysis
References:
1. J.C. Giddings, Anal. Chem., (1962) 34 314-319.
2. M.E. Hail, R.A. Yost, Anal. Chem. (1989) 61 2402-2410.
3. M. van Deursen, H. G. Janssen, J. Beens, P. Lipman, R. Reinierkens, G. Rutten, C. Cramers, J. Microcol. Sep., (2000) 12 613‐622.
4. J. de Zeeuw, J. Peene, H.-G.Janssen, X. Lou, J. High Resol. Chromatogr., (2000) 23 677-680.
5. Y. Sapozhnikova, S.J. Lehotay, Anal. Chim. Acta (2015) 899 13-22.
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