Page 191 - Illustrated Pocket Dictionary of Chromatography

SYSTEM PEAK 193

C

This is an example of a gastight syringe. Note the PTFE-tipped plunger, the open-
close valve, and the pointed-end needle for puncturing septa.

£1mL, a plunger-in-needle is used (i.e., the sample does not enter the
barrel).

syringe barrel Contains all components of a solid-phase extrac-
tion column: frits and packing material. Typical materials of con-
struction include polypropylene, glass, or PTFE. Also see syringe.

systematic error One that cannot be determined from repetitive
analysis. Rather, this type of error consistently over- or underesti-
mates the true value. See bias.

system peak The result of a solvent mismatch between the sample
solution and the mobile phase and is often seen as a set of paired
peaks. Any time that the solvent used to inject the sample is not iden-
tical to the composition of the mobile phase and the mobile phase
generates a “non zero” detector response, a system peak may be
observed. There are frequently two peaks, one positive-going (due to
zone enrichment of a mobile-phase component) and the other nega-
tive-going (due to depletion of a mobile-phase component).