Page 189 - Illustrated Pocket Dictionary of Chromatography

SYRINGE 191

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range from 10 to 450m /g corresponding to pore sizes of 4000–50Å,
respectively.
surrogate A compound that is not part of the sample matrix and
is added to a sample before the preparation step. Its recovery is mon-
itored along with other sample analytes, and its overall recovery is a
direct evaluation of the performance of the entire method. In many
respects a surrogate is similar to an internal standard in that it cannot
be in the sample matrix, should be similar in chemical/physical prop-
erties to the analyte(s) of interest, and cannot coelute with any com-
ponent in the sample. The difference is that a surrogate is not used to
“correct” a result as an internal standard is.

swelling The process by which a dry resin or gel imbibes solvent
and expands. Particle size and pore diameter are strongly affected
by this, and so before use a resin must be fully equilibrated with the
operating solvent. See shrinking.

system suitability A term used to describe a series of tests that
are conducted over the course of an analysis to support the fact that
the system was operating within acceptable parameters during the
analysis. Some parameters that could be monitored include: resolu-
tion, tailing, and response factor. Standards and check samples (pre-
viously analyzed samples having predetermined values) are also part
of system suitability testing.

symmetry The measure of how closely the peak elution profile is
a mirror image around the peak maximum. For a chromatographic
peak the departure of a peak from being perfectly symmetric is
represented through the use of an asymmetry factor.
syringe Used in most GC injection systems and in manual HPLC
injection systems to introduce the sample into the mobile phase flow
stream (GC) or the injector loop (HPLC). A syringe consists of a body
(e.g., glass) that is precision bored, a matched plunger (e.g., stainless
steel), and a needle (stainless steel). The barrel is marked for volume,
and the plunger is used to draw up and expel sample from the barrel.
For GC the needle is beveled to make it easier to puncture the septum,
whereas in HPLC the needle is often squared so that it forms a
seal with the injector port inlet. Gastight syringes often have the
plunger terminating with a ribbed PTFE cap to prevent gas from
leaking out between the barrel and the plunger. For samples that
are ≥1mL in volume, a plunger-in-barrel is used. For samples that are