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By Janna Peters on Friday, July 9, 2004 - 07:26 am:
Hello!
I hope that someone in this forum has an idea where my gc-trouble comes from, because I am at my wits´ end. We have a new cold injection system (Gerstel CIS 3)and we plan to do large volume injections with FAMEs in hexane. Until now I am not able to produce a stable baseline with just using hexane, because I often have quite large ghost peaks in my chromatogramme. After several runs with hexane most of them are gone but suddenly (after I have not used the GC for several hours) they reappear. I already changed the liner, cutted the column, changed the solvent (new bottle of suprapur hexane for GC), the needle, heated the column and the CIS (the later up to 350°C).
Here is my priliminary program:
Injection volume: 10µl (speed 2 µl/min)
CIS Inital temp. -40°C for 0.85min, rate 12°C/S up to 280°C (für 3 min)
vent flow 50 ml/min
vent time 0.8 min
purge time 1.8 min (leading to 1 min splittless)
purge flow 100 ml/min
Gassaver after 16 min with 16 ml/min
Liner: buffeled liner
Column: DB-FFAP (polar)
column flow 0.8 ml He/min
Oven 80°C(5min) rate1 30°C/min to 165°C rate2 4°C/min 240°C(15min)
FID Detector
Does anyone have a clue, where these peaks might come from or what else I could do to get a reproducible run? We still use the same gas as we did befor with the split injection, therefor I exclude contamination by the gases.
And I would be happy to get tips for the still preliminary method as well.
Thank you very much in advance!
Janna
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By Ron on Wednesday, July 14, 2004 - 04:40 am:
It is very likely the contamination is from the carrier gas. You are now using a different injection technique with the injection port kept cold instead of hot, so if there are heavier contaminant in the gas they will now condense out in the injector and be transferred to the column.
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By ingochrist on Tuesday, July 20, 2004 - 10:00 am:
My first guess would also be your carrier gas. But if that is not the case, my next best guess would be that the contamination comes from your split line. Clean it with Methanol or Ethanol and bake the system overnight. If you still have a high background, use some heating device directly on the split line.
Hello!
I hope that someone in this forum has an idea where my gc-trouble comes from, because I am at my wits´ end. We have a new cold injection system (Gerstel CIS 3)and we plan to do large volume injections with FAMEs in hexane. Until now I am not able to produce a stable baseline with just using hexane, because I often have quite large ghost peaks in my chromatogramme. After several runs with hexane most of them are gone but suddenly (after I have not used the GC for several hours) they reappear. I already changed the liner, cutted the column, changed the solvent (new bottle of suprapur hexane for GC), the needle, heated the column and the CIS (the later up to 350°C).
Here is my priliminary program:
Injection volume: 10µl (speed 2 µl/min)
CIS Inital temp. -40°C for 0.85min, rate 12°C/S up to 280°C (für 3 min)
vent flow 50 ml/min
vent time 0.8 min
purge time 1.8 min (leading to 1 min splittless)
purge flow 100 ml/min
Gassaver after 16 min with 16 ml/min
Liner: buffeled liner
Column: DB-FFAP (polar)
column flow 0.8 ml He/min
Oven 80°C(5min) rate1 30°C/min to 165°C rate2 4°C/min 240°C(15min)
FID Detector
Does anyone have a clue, where these peaks might come from or what else I could do to get a reproducible run? We still use the same gas as we did befor with the split injection, therefor I exclude contamination by the gases.
And I would be happy to get tips for the still preliminary method as well.
Thank you very much in advance!
Janna
-------------------------------------------------------------------------------------------------------
By Ron on Wednesday, July 14, 2004 - 04:40 am:
It is very likely the contamination is from the carrier gas. You are now using a different injection technique with the injection port kept cold instead of hot, so if there are heavier contaminant in the gas they will now condense out in the injector and be transferred to the column.
-------------------------------------------------------------------------------------------------------
By ingochrist on Tuesday, July 20, 2004 - 10:00 am:
My first guess would also be your carrier gas. But if that is not the case, my next best guess would be that the contamination comes from your split line. Clean it with Methanol or Ethanol and bake the system overnight. If you still have a high background, use some heating device directly on the split line.
