Page 112 - Illustrated Pocket Dictionary of Chromatography

ION-EXCHANGE SUPPORTS 109

where F is the flow rate, A is the cross-sectional area of the column,
and e o is the interstitial porosity.

The volume in a column excluding the
interstitial volume, V e
volume of the packing material (and its pore volume).
e The fraction of volume of the packing
intraparticle porosity, e i
material itself, V pack, that is pore volume, V pore:
e i = V pore V pack

intraparticle volume, V i Also called pore volume; the volume of
the pores contained within the packing material. This value is exper-
imentally determined through the use of mercury porosimetry or the
BET nitrogen adsorption method.
intrinsic viscosity, [h] Used in the generation of a universal
calibration curve (i.e., a viscometric detector monitors this) for
polymers:

[]M = ( f V e )
h
where M is the molecular weight and f(V e) denotes a function of the
elution volume. The intrinsic viscosity is the limiting value of the
reduced viscosity at infinite dilution of the analyte. Alternatively:
[] h sp c ,
h = lim
c Æ 0

where h sp = (h-h o)/h o and h is the viscosity of the solution and h o is
the viscosity of the solvent.

ion-exchange chromatography (IEC) An LC technique that
generates a separation through ionic interaction. The support mate-
rial has a permanent positive or negative change and retains analytes
of the opposite charge. Elution is accomplished through adding com-
peting ions (same charge as analyte) to the mobile phase.

ion-exchange supports Materials that have permanent charged
functional groups on the surface. Anion-exchange supports (those
supports used to separate anions) have positively charged groups,
whereas cation-exchange supports have negatively charged groups.