Page 206 - Academic Press Encyclopedia of Physical Science and Technology 3rd Analytical Chemistry

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Encyclopedia of Physical Science and Technology EN008B-382 June 30, 2001 18:58

Liquid Chromatography

Neil D. Danielson
Miami University

I. Analytical HPLC
II. Small- and Large-Scale HPLC
III. Separation Techniques
IV. Development of Separation Strategy
V. Sample Derivatization Chemistry

GLOSSARY rates neutral compounds by partitioning into the liquid
in between and inside the ion exchange beads as well
Bonded-phase packing Stationary support such as silica as adsorption on the polymer backbone.
having chemically attached functional groups. Ion-pair chromatography Reversed-phase separation
Capillary electrochromatography A hybrid of capil- of charged compounds by addition of an oppositely
lary electrophoresis and HPLC involving mobile phase charged reagent to the mobile phase.
transport by electrosmotic flow not by pump pressure Normal-phase Type of liquid chromatography in which
through a packed capillary column. the stationary phase is polar (e.g., silica) and the mobile
Dead volume Any volume between the injector and de- phase is nonpolar (e.g., hexane).
tector such as in connecting tubing and fittings where Pellicular packing Column packing consisting of solid
separation does not occur. glass beads enveloped with a 1–2-µm porous layer.
Elution Removal of sample components from a column. Reverse(d)-phase Type of liquid chromatography in
Gradient elution Changing the mobile phase composi- which the stationary phase is nonpolar (e.g., C-18 hy-
tion with time at a specified rate during the chromato- drocarbon) and the mobile phase is polar (e.g., water–
graphic separation. methanol).
Guard column Short column attached in front of the Size exclusion Type of liquid chromatography that sepa-
separation column to adsorb compounds that could ratessamplecomponentsbymolecularsizegenerallyin
degrade the latter column. order from increasing to decreasing molecular weight.
Ion chromatography Rapid and efficient ion-exchange Solute The separated species on analyte.
separation of ions usually with conductivity detection.
Ion-exchange Typeofliquidchromatographyforthesep-
aration of ions based on their charge affinity for the THE SEPARATION of compounds or ions as they pass
ionic functional groups of the column packing. down a column due to the differing distribution of the
Ion-exclusion Type of liquid chromatography that sepa- sample components between the liquid mobile phase and

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