Page 33 - Illustrated Pocket Dictionary of Chromatography

28 CARTRIDGE

not clean. This is particularly crucial when the injection solution
changes from a weak solvent to a strong one. The strong solvent often
solvates compounds deposited in the injector loop.
cartridge (1) This term has become hopelessly confused and can
apply to the syringe-type barrel column (as per EPA documents) or
the luer-top/luer-exit configuration. See solid phase extraction. (2) The
housing used to contain columns with removable endfittings.
cartridge column Consists of the housing, packing, and frits. In
essence, it is a column without endfittings. To use the cartridge, it is
placed within a cartridge holder that fits snugly around the cartridge
to prevent leakage under pressure.

Shown on the right-hand side of the column is a disassembled cartridge column
endfitting. Note that the frit is internal to the column tube. This means that the frit
cannot be replaced in a cartridge column as it can in a conventional endfitting
column. Because there is no ferrule, another mechanism for setting the endfitting
to the column is used: a C ring that fits into a grove on the column tubing. The
cartridge endfitting is finger tightened (note knurled body on the two endfitting
pieces.) An assembled endfitting is shown on the left-hand side of this column.

cathode In techniques where voltage is applied (i.e., electrolytic,
not galvanic), a cathode is a negative electrode toward which cations
migrate.

cation A molecule or atom that bears a positive charge.
cation exchange A cation-exchange material has a permanent
negative charge on the surface and is used to separate cationic com-
pounds (positively charged species). The type of negative charge
(e.g., carboxylate, sulfonate) and its concentration on the surface,
expressed in milliequivalents/gram, the substance to be eluted, and