Page 141 - Illustrated Pocket Dictionary of Chromatography

P

packing In LC columns, packed-bed GC columns, and many
sample preparation components (e.g., SPE), the process of placing
the packing material into the column. Dry packing is commonly used
in packed-bed GC columns and sample preparation components,
whereas slurry packing is used for HPLC columns.

packing material The material contained within LC, packed-bed
GC, and sample preparation components. Packing material is also
called support material, packing, and stationary phase. Packing mate-
rials vary in particle size and shape, chemical identity, base material,
pore size, and pore volume.

paired-ion chromatography (PIC) An LC technique used
to separate charged or chargeable analytes on a reversed-phase
support by creating an associated molecule through the addition
of oppositely charged ions to the mobile phase. The resulting com-
plex is overall charge neutral and has a much longer retention than
the charged species. Quaternary amines are frequently used for
anionic analytes and sulfonic acids for cationic analytes. See ion-pair
reagent.

paired-ion reagents See ion-pair reagent.

particle diameter, d p Often the average diameter obtained from
the distribution of the particle sizes in a given production batch of
material. Although the average diameter of the packing material is
important, the range of sizes is also critical to the overall efficiency
of a column manufactured from this material and cannot be deter-
mined from the particle diameter information alone.

partition chromatography An LC technique that utilizes a liquid
as a stationary phase, typically adsorbed to the support surface. This
is difficult to do because the stationary phase bleeds off the column
over time, resulting in an ever-changing amount of stationary phase
present in the column. Current theory also places bonded phases in

Illustrated Pocket Dictionary of Chromatography, by Paul C. Sadek.
ISBN 0-471-20021-2 Copyright © 2004 John Wiley & Sons, Inc.
141