interstitial volume

in gas chromatography
https://doi.org/10.1351/goldbook.I03122
The volume $$V_{\text{G}}$$ of the column not occupied by the liquid phase and its solid support, or by the @A00109@. It does not include any volume external to the column, such as the volume of the sample injector or of the detector.
Source:
Orange Book, 2nd ed., p. 99 [Terms]