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F • Glossary
Doc. 065291-01 3/09 261
of relatively clean sample. This allows large volumes of sample to be injected,
lowering concentration detection limits.
Conductivity
A measure of the ease with which electrical current flows through a liquid
contained between two opposite charged electrodes. Conductivity is a
characteristic of ions in solution. Units are siemens.
Counterion
Ions carrying a charge opposite that of the sample ions (e.g., Na
+
) may be the
counterion of a Cl
-
analyte. These ions preserve electrical neutrality in solution.
% Crosslink
Divinylbenzene content in a polystyrene/divinylbenzene (PS-DVB) resin; this
contributes to the mechanical strength of the resin and determines
chromatographic properties.
Equivalent Conductivity (
λ)
The contribution of an ionic species to the total conductivity of a solution as
measured in a standard cell having electrodes 1 cm
2
in area and exactly 1 cm
apart.
Guard Column
A small column that prevents poisoning of the separator column by sorbing
organic contaminants and removing particulates. It is filled with the same packing
as the separator column. Synonymous with Pre-Column.
HETP (H)
H
eight Equivalent to a Theoretical Plate. A measure of column efficiency which
allows comparison between columns of different lengths.
HETP = H = L/N
Where: L = the column length (in mm)
N = the number of theoretical plates
Ion-Exchange Capacity
The number of active ion exchange sites in a given weight or volume of resin; this
is usually expressed in meq/g or meq/mL.
Ion-Exchange Resin
An insoluble polymer matrix containing fixed-charge exchange sites (anionic or
cationic). IC resins are formed into small spherical particles (beads).