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2. That the cold trap is not
overloaded with solvent or
analytes. Split discrimination
and / or peak splitting may be
observed if the trap is allowed to
become overloaded with volatile
solvent or water.
Double split During double split operation the split
is open both during tube desorption
and trap heat.
As above for single split operation.
During splitless operation:
Flow through tube during tube desorption = Desorb Flow
Flow through trap during tube desorption = Desorb Flow
Flow through trap during trap heat = Column Flow
During single split operation:
Flow through tube during tube desorption = Desorb Flow + Split Flow (if selected)
Flow through trap during tube desorption = Desorb Flow
Flow through trap during trap heat = Column Flow + Split Flow (if selected)
During double split operation:
Flow through tube during tube desorption = Desorb Flow + Split Flow
Flow through trap during tube desorption = Desorb Flow
Flow through trap during trap heat = Column Flow + Split Flow
2.4.12 UNITY 2 systems with Electronic Carrier Control (ECC)
When installed with certain models of commercial GC(-MS), UNITY 2 systems can be configured with
electronic control of the carrier gas as it leaves the cold trap and enters the fused silica (or length of
analytical capillary column) inside the transfer line. In this case, manual adjustment of the desorb and
split flows, as described above, is still required.
Key benefits of electronic control of the carrier gas through the column include retention time stability
(even when split flows are changed significantly) and pressure programming for enhanced
chromatographic performance with higher boiling compounds.
For further information see the Electronic Carrier Control (ECC) Installation Manual.
2.4.13 UNITY 2 systems configured with Electronic Mass Flow Control
Mass Flow Control Accessories are available and offer automatic adjustment and closed loop control of
the flows during the thermal desorption cycle. For example, this means that different split flows can be set
for each of these different phases of operation. The accessories also offer electronic flow readout during
manual adjustment of the desorb flow.
For further information see the MFC Installation Manual.
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