RestekCapillaryColumn InstallationGuide, Section II
Table III Typical Split Vent FlowRates (50 to1 split ratio)
Carrier gas 0.18mm ID 0.25mm ID 0.32mm ID 0.53mm ID
helium 15cc/min.
35cc/min.
80cc/min.
125cc/min.
hydrogen
30cc/min.
70cc/min.
160cc/min.
250cc/min.
Safety Tip: Always use a split vent trapwhen injecting hazardous or carcinogenic chemicals into a split/splitless inlet
system.
GoodOperatingPractice
Operating a columnwithout carrier gas flow causes irreparable damage to the
stationary phase. Confirm flow by inserting the column outlet into a vial of solvent such
as acetone or isopropyl alcohol prior to installing it into the detector. The appearance of
bubbles at the column outlet confirms carrier gas flow. Allow the column to purgewith
carrier gas for fifteenminutes before installing the column outlet into the detector to
remove any room air that may have diffused inside the column.
Outlet Installation
Install the nut and ferrule to the detector in themanner described in the instrument
manual. Gently insert the column end into the outlet fittingmaking sure that it is not
crushed or scraped against themetal detector parts. Regardless of the GC
manufacturer, a higher degree of inertness and better peak symmetry results if the
column end can be installed 1 to 3mm from the detector jet orifice. Be careful not to
push the column beyond the jet orifice or the column endwill burn in the flame. Some
jets are too narrow to insert the column close to the jet orifice. If this is the case, pull
the column end approximately 2mm away from the narrowed point to prevent flow
occlusion or loss of inertness. Whilemaintaining the correct insertion distance, use a
capillarywrench to tighten the nut approximately one-half turn past finger-tight until
the column is held firmly. The ferrule is tight when the column cannot be pulled from
the fittingwhile applying gentle pressure.
Note— Be cautious when using stainless steel or aluminum-clad columns in gas
chromatographs or GC/MS systems with electrically energized detector jets or orifices.
These columns will conduct electricity and cause a short if the end of the column is
installed too far into the energized detector. Always turn off the electrometer with
Varian, PerkinElmer, and Shimadzu FIDs (since the detector is not grounded) when
installing stainless steel or aluminum clad columns.
Leak-Checking Techniques
The best way to leak-check a capillary column system is to use a thermal conductivity
leak detector (cat.#22451)*. These portable devices detect minute traces of helium or
hydrogen carrier gas without contaminating the system. Leaks inmass spectrometers
can easily be determined bymonitoring for Mass 28 (N
2
) or 32 (O
2
).*
Never use liquid leak detectors that contain soaps
or surfactants in capillary chromatography. Leaks
draw thesematerials inside the system and
contaminate the column, making high sensitivity
operation difficult. In addition, liquid leak detectors
can cause permanent damage to the capillary
column by depolymerizing the silicone stationary
phase.
Once the system is leak-free, set the injector and
detector temperatures approximately 20°C above
the final operating temperature of the analysis or at
the column'smaximum operating temperature.
Then light or turn on the detector. Caution: Do NOT
exceed themaximum operating temperature of the
