Page 208 - Illustrated Pocket Dictionary of Chromatography

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VOID VOLUME, V M
visualization reagent/technique In thin-layer chromatography
a visualization reagent is used to make an analyte band appear on
a plate. The reagent used can be compound- or class specific (e.g.,
ninhydrin for amines) or general (sorbent contains a fluorescent
label that is quenched by the presence of the analyte).
void An empty volume found at the top of the packing bed of a
column. Voids often occur at the top of a column, where packing mate-
rial is slowly dissolved and carried away by the mobile phase. Empty
volume that occurs within the column packing bed is called channel-
ing. Both result in decreased efficiency, often seen as tailing. Severe
enough voids/channeling will result in split peaks.

void time, t o The time required for an unretained unexcluded
analyte to travel from the injector to the detector.

void volume, V M Determined from the void time, t o, and flow rate,
F:
V M = t o ¥ F

Note that this is not the column volume alone but includes the injec-
tor, connecting tubing, and detector volume as well.