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Instruction for installing GC columns
How to install a GC column? A short explanation in simple steps.
1. Equipment preparation
Cool all heatable zones.
Check the carrier gas purification system (oxygen and moisture) and replace depleted cartridges.
Insert a new septum into the inlet. If necessary, clean or replace the inlet liners and the inlet seals.
Check or renew the detection directions. If necessary, clean or replace the detector nozzle.
2. Column preparation
Check the column for any damage or breakage.
Insert the column into the retainer of the column oven. There is no specific orientation, usually the staves of the column are pointing towards the door of the column oven. The column should be installed in the center of the oven in order to ensure a uniform heat supply and thus stable retention times. Be careful that the parts do not rub against the column.
Unwind the column on both sides to such an extent that the injector and the detector can be reached with a straightly bent column piece (approx. 50 cm).
Place the column nut and ferrule on the column's inlet end. Slide the nut and ferrule about 15 cm onto the column.
Shorten the column with a column cutter by approx. 5 cm.
Press the part to be cut against one finger and scratch the column without cutting it all the way through. Take the column between thumb and index finger closely to the notch and bend it away from the notch. The column should break easily. If the column does not break easily, repeat the same procedure at a different location of the column.
Check the fraction’s edge with a magnifying glass. The cut should be straight. If necessary, re-cut at a different location.
3. Column installation
Observe the correct installation depth when installing the column. You can find them in the GC manufacturer's manual.
Connect the column to the inlet first. Push the column nut and the ferrule to the correct distance and mark the position with corrective liquid (tip-ex) immediately behind the column nut.
Then insert the column into the injector and screw the column nut in tight with your fingers. Then tighten the nut for a further ¼-½ turn with an open-ended jaw spanner so that the column cannot be pulled out of the fitting. Use the mark to verify that the correct distance is observed.
Turn the carrier gas up and set a suitable flow rate. Set the inlet pressure, split flow and septum flush flow to the appropriate values. The purge valve must be open for a split/splitless injector.
Check if the carrier gas flows through the column by immersing the free end of the column into a vessel containing solvent. A uniform stream of bubbles should appear. If this is not the case, check the settings for the carrier gas supply and check the system for leaks.
Rinse the column at low temperature (40 ° C) with carrier gas for at least 5 min in case of a 25-30 m long column or for at least 10 min in case of a 50-60 m long column.
Insert the column into the detector. Proceed as described for the inlet.
Check the system for leaks, for example by using an electronic leak detector. Heating up a column without a proper carrier gas flow or if oxygen is contained in the carrier gas can quickly and permanently damage the column!
Set appropriate temperatures as well as suitable makeup and detector gas flows for the injector and the detector and activate the detector. Do not exceed the maximum working temperature of the column in order to avoid damage!
Inject a non-retarded substance to control the installation on the detector‘s side and in order to determine the dead time.
The peak will be symmetrical in case of a correct installation. If necessary, adjust the carrier gas flow. The installation at the inlet must be repeated in case peak tailing occurs.
4. Column conditioning
Condition the column for one to three hours 20°C above the final temperature of your temperature program or at the maximum working temperature of the column (depending on which temperature is lower). Compare the values of the subsoil with those of the column specification after 10 min. If they do not match, check the system for leaks again.
For most applications, one hour of conditioning is sufficient to achieve a flat, constant baseline. It is recommended to extend the conditioning time for analysis with sensitive detectors or for trace analysis. The column can be heated up to the maximum temperature for an extended period of time without any considerations. There is no negative effect on column performance as long as you ensure that the carrier gas is clean and oxygen and moisture are filtered.
If the column is not connected to the detector during conditioning, you may achieve a faster stabilization of the base line with EC or MS detectors. Also for columns with a film thickness > 1 μm, it is recommended to condition them without being connected to the detector. If the column is conditioned while being open, shorten it by 10-20 cm before connecting it to the detector.
5. Check the column
Check the mean linear carrier gas velocity.
Perform a blank run and save the chromatogram for future comparisons. The chromatogram should not contain peaks. Peaks indicate impurities, generally located in the inlet area. With increasing attrition of the column during normal use, the degree of baseline increase elevates. In case the baseline increases at a significantly lower temperature than in previous measurements, the column is likely to be contaminated or damaged.
In order to check the performance of your system, analyze a column test mixture for a new method or standard to ensure the correct performance of the column and system.
The column can remain in the device with carrier gas flow and a temperature of 100-150 °C for a short time, for example in case you want to carry out further measurements on the following day. For longer periods of time or in case you want to replace the column, remove the column from the device. Close the column by gently pushing a piece of septum on each end. Keep the column in the original packaging and protected from light.