Flip Seal Inlet Seals
Frequently Asked Questions

By Jack Cochran

1. What is the Restek Flip Seal inlet seal?
The Restek Flip Seal inlet seal is a special reversible type of dual Vespel ring inlet seal for the Agilent 5890/6890/7890 split/splitless GC inlet. With the one-time installation of a special reducing nut adaptor fitting (cat.# 23406), one seal can be “flipped” and used twice, unlike the typical seal used on the bottom of the inlet, which is only used once and then discarded.

2. Why did Restek develop this new type of seal?
Preventative maintenance can save labs money in the long run, but many analysts don’t perform this critical step as frequently as they should due to economic or scheduling concerns. We wanted to reduce the cost of maintenance so that customers had the opportunity to prevent problems through more frequent routine maintenance of their Agilent GC inlets. Since the inlet is where GC system failures occur first, especially with dirty sample introductions, regular maintenance can prevent unexpected downtime and costly sample reanalysis. We recommend that customers replace the GC septum, the GC inlet liner, the liner O-ring, and the inlet bottom seal simultaneously when doing preventative inlet maintenance. By developing a seal that can be used twice, we make preventative maintenance more economical for our customers.

3. How do I install a Flip Seal inlet seal?
It’s easy and essentially the same as installing a standard seal on the Agilent GC inlet. Instructions are included with the seals, but here are the basic steps. Note that you will need to replace the original Agilent inlet fitting with a Flip Seal reducing nut adaptor fitting (cat.# 23406), if this has not already been done. To install the seal, first remove the nut warmer cup and inlet fitting. Next place a Flip Seal inlet seal in the bottom of the adaptor fitting and screw the fitting onto the bottom of the Agilent split/splitless inlet until hand-tight. Tighten the fitting only an additional ¼ turn with a ½” wrench; the dual Vespel seal does not require extensive tightening. Finally, reinstall the nut warmer cup over the adaptor fitting.

Flip Seal inlet seal in adaptor fitting.

Adaptor fitting in inlet.

Nut warmer cup installed over
adaptor fitting.


4. How do I install a GC column into the new Flip Seal adaptor nut?
Insert the GC column through the 1/16” adaptor sealing nut and a standard 1/16” graphite or graphite-Vespel capillary ferrule. Make a clean cut across the GC column. Install the column into the adaptor 30-32 mm from the bottom of the 1/16” nut, which places the column end a few millimeters above the bottom of the inlet seal, the perfect installation distance! Don’t forget to leak check with a Restek Electronic Leak Detector (cat.# 22655) after tightening the adaptor nut to seal the GC column to the inlet and re-pressurizing the inlet.


Seat the column sealing nut so that
the bottom is 30-32 mm from
the end of the column.

Insert the column into the adaptor fitting.

Tighten the sealing nut onto the adaptor fitting.

Perfect installation distance for column in adaptor fitting.


5. Are there recommended GC inlet liner types for use with this seal?
Restek recommends a 4 mm ID Restek Premium single taper liner with wool (cat.# 23303) for splitless injections and a 4 mm ID Restek Premium Precision liner with wool (cat.# 23305) for split injections. The thoroughly deactivated Restek Premium wool provides excellent sample homogenization during either splitless or split injection, which increases repeatability and accuracy. In addition, wool keeps liquid sample from being deposited on the inlet seal, where contact with hot metal can degrade thermally sensitive compounds, or where less volatile, higher molecular weight compounds of interest can be lost. Wool also protects the GC column from non-volatile sample “dirt”, preserving the column’s chromatographic performance, especially for difficult to analyze compounds.

6. How often should I flip the seal?
As mentioned earlier, best preventative GC inlet system maintenance practice dictates changing the GC inlet septum, the GC inlet liner and O-ring, and the inlet seal, simultaneously. This can be done on a timed basis (daily, weekly, etc., depending on the number of samples analyzed) or after analysis of a standard indicates sub-par GC performance.

7. Do I need to do anything before reinstalling the flipped seal?
In almost all cases, no, but if you drop the seal or notice any residue on the fresh seal surface, wipe it off with a lab tissue moistened with acetone.

8. I dropped my Flip Seal inlet seal during reinstallation. How can I tell which side was previously installed towards the GC inlet?
Simple—just look closely at the Vespel rings. The one with the cut from the inlet knife edge shows the side of the seal that was previously installed up towards the inlet. Make sure that side is down for the flipped reinstallation.


New, unused side

Previously installed side