PerkinElmer CLARUS 590 GC, User Manual

Page: 20 / 284

20 . Clarus 590 GC User’s Guide
Mobile phase – The gas which carries the solute (sample) along and over the column material. This
carrier gas is inert and usually helium, nitrogen, or hydrogen.
Noise
– Background signal fluctuations arising from a detector response. This response is the result of
the column installed, carrier gas purity, electronic components, etc. The response of any detector is
defined by the signal-to-noise ratio.
Partition Coefficient
– The differential solubility of a substance in two different phases. In the case of
gas–liquid chromatography, the sample components reach an equilibrium between the gas phase
(mobile) and the liquid phase (stationary). Each component has a different partition coefficient thus
causing separation in the column.
Pressure programming – Pressure control through an independent four-step, three-ramp program for
each carrier gas channel.
Resolution
– The degree of separation between two peaks.
Retention time
– The time interval from the point of injection to the appearance of the peak maximum,
of a component’s signal.
Septum
– Silicone rubber material placed in the injection port through which the injection is made.
When the needle is withdrawn, the silicone rubber reseals, thus not allowing any sample or carrier gas to
escape.
Stationary phase
– The liquid or solid adsorbent portion of the column that retains components passing
through the GC column.
Subambient – Below ambient temperature. The oven cools down below ambient temperature with the
use of either liquid nitrogen or liquid carbon dioxide.
Syringes
– Precision dispensing devices used to deliver sample to the GC. Liquid and gas syringes are
available.
Tailing
– When a peak is not symmetrical or Gaussian shaped but the back end is broadened, it is said
to be tailing.
Temperature programming
– A technique commonly used to increase the rate of elution of the
components. After the sample is injected into the oven at a specific temperature, the temperature
program increases the oven temperature to the prescribed temperature at a defined rate (in ° C/min).
Unretained peak
– A component that is not retained by the column. The time taken for an unretained
sample to pass through the column is the same time as the time taken for the carrier gas to pass
through.
Velocity programming
– Programmed linear velocity where the PPC controller interprets stored PPC
programs as the average capillary column linear velocity settings.