Page 206 - Illustrated Pocket Dictionary of Chromatography

VISCOSITY, h 209

vespel A polyamide polymer that is used in capillary GC column
unions mainly as the ferrule. Vespel is not easily deformed and there-
fore is excellent for high-pressure use. It can also sometimes be
reused (unlike graphite ferrules). Modified vespel comes impregnated
with 10–40% carbon.
vicinal Literally means “close to” or “nearby” and is used in the
description of surface silanol groups. As opposed to isolated nonin-
teractive silanol groups, vicinal silanols groups are spatially close
enough to hydrogen bond with one another:

Si O
Surface O H

Si O
H
Vicinal silanol group

viscosity, h A measure of the mobile-phase resistance to flow. The
system operating pressure is directly proportional to the viscosity of
the mobile phase. Viscosities of mixtures are not derived from the
mole percent in the mix and the pure viscosity for each component.
As seen below, viscosity is a complex function and is dependent on
strong interactions between components in the mobile phase (such
as hydrogen bonding, etc).