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- Posts: 5
- Joined: Fri Aug 11, 2017 9:26 pm
This is my first time to post my question regarding very strange GC carry-over I met in testing, hope I will get your kindly suggestion and help.
Method: Test acetic acid in propionic anhydrate by GC
Sample preparation: Hydrolyze the sample with water by steam bath heating, then dilute with acetone.
Standard preparation: Appropriate volume of acid, add the same volume of water as sample preparation.
Instrument: GC 6890N, Column: Glass column: supelco 10% SP1200 1% H3PO4
Unexpected chromatograms:
1. After 6 injections of standard, the very high carryover of acetic acid could be observed in the chromatogram of the first injection of sample, almost as high as standard, then rapidly disappeared in second and afterward sample injections.
2. if I inserted a blank injection of acetone immediately after the six injections of standard, the chromatogram of blank is very clean, no any carry-over, however, then I injected a sample after blank, the high carryover came again.
3. I have changed the septum, syringe, re-connected column, and not improve.
Please, anyone, have any idea can share, I will appreciate very much.
Many thanks.
1997