Page 50 - Illustrated Pocket Dictionary of Chromatography

CROSS-LINKING 45

The crimping tool is used to seal the cap to the vial.

critical micelle concentration (CMC) The concentration at
which surfactant (surface active agents that have a hydrophilic head
and hydrophobic tail) molecules change their state from predomi-
nantly independently dispersed to mostly aggregated. The aggregated
surfactant molecules are called micelles. Formation of micelles
in solution often produces dramatic changes in the physical and
chemical properties of the solution such as surface tension and
conductivity.

critical point The temperature and pressure at which a substance
becomes a critical fluid, that is, the point where a gas can no longer
be converted into its corresponding liquid occurs at the substance’s
critical point.

The lowest pressure that would cause a
critical pressure, p c
substance to liquefy when held at its critical temperature. See SCF
(supercritical fluid).
The maximum temperature at which a
critical temperature, T c
substance in its gas form can be converted to its corresponding liquid
by an increase in pressure. See SCF (supercritical fluid).

cross-linking When polymeric support material is prepared from
monomers, the monomers are chemically bonded together through a
process called cross-linking. A commonly used cross-linking reagent is
divinylbenzene used in the production of polystyrene-divinylbenzene
copolymers that are base resins for many ion-exchange support
materials.