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By Anonymous on Sunday, June 13, 2004 - 02:53 pm:
Hello,
I want to know how to troubleshoot when there is too much of drift in retention times for my compounds. I have not been able to get even one run with the same retention time.
I am using HP 5890 series II and FID. The initial oven temperature is 70 C and initial time is 0.1 min then the rate is 10 deg/ min upto a final value of 100 then with another ramp rate of 20 deg/min it goes upto 160 C and stays for a minute.
1)Is it necessary to wait for each run to reach the until the final oven temperature? i.e, if the compounds come out in less than 3 mins while it takes 7 mins for the entire run to complete?
2)The operating conditions have not changed but a wide dispersion is noticed in retention times and total area count.
I am analysing primary alcohols.
Please post your suggestions regarding this problem.
Thanks
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By Yury on Monday, June 14, 2004 - 05:29 am:
Of course you must start every run at the same oven temperature and wait when a run be finished. If you don’t do this for your measurements, then that’s the cause you get such a huge for GC drift.
Also I advise you to condition your column at 250 degrees and open carrier gas flow overnight, because if your GC runs are never finished, your column should be nicely contaminated...
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By Consumer Products Guy on Monday, June 14, 2004 - 11:23 am:
We don't have any problems with primary fatty alcohols, either "as is" or as trimethylsilyl derivatives.
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By Ron on Monday, June 21, 2004 - 06:22 am:
In addition to making sure the column oven equilibration time is long enough and that the GC is not injecting before the oven is ready, check for leaks at the inlet, especially if you have variation in area counts of standards as well as retention time variations.
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By meat head on Saturday, July 10, 2004 - 10:49 am:
clean your spliter
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By jay on Friday, July 16, 2004 - 04:17 am:
I think leak at injector side
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By ced on Monday, July 19, 2004 - 02:21 am:
Check and change your septum...
Check your column connection at the injector port.
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By Chromatographer1 on Monday, July 19, 2004 - 05:26 am:
Another problem may lie in underivitized alcohols is the peak assymetry with overloaded peaks. The retention time will change with concentration. Since you noted the area counts vary greatly, you may have 'American Motors' logo shaped peaks (I know that statement dates me). In this case, a picture would be worth a million words, but no chromatogram to review is our case sadly. Good luck.
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By GPS on Monday, July 19, 2004 - 09:32 am:
When we mean the retention time is consistent, do we consider till the third decimal (*.***) ?
Hello,
I want to know how to troubleshoot when there is too much of drift in retention times for my compounds. I have not been able to get even one run with the same retention time.
I am using HP 5890 series II and FID. The initial oven temperature is 70 C and initial time is 0.1 min then the rate is 10 deg/ min upto a final value of 100 then with another ramp rate of 20 deg/min it goes upto 160 C and stays for a minute.
1)Is it necessary to wait for each run to reach the until the final oven temperature? i.e, if the compounds come out in less than 3 mins while it takes 7 mins for the entire run to complete?
2)The operating conditions have not changed but a wide dispersion is noticed in retention times and total area count.
I am analysing primary alcohols.
Please post your suggestions regarding this problem.
Thanks
-------------------------------------------------------------------------------------------------------
By Yury on Monday, June 14, 2004 - 05:29 am:
Of course you must start every run at the same oven temperature and wait when a run be finished. If you don’t do this for your measurements, then that’s the cause you get such a huge for GC drift.
Also I advise you to condition your column at 250 degrees and open carrier gas flow overnight, because if your GC runs are never finished, your column should be nicely contaminated...
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Monday, June 14, 2004 - 11:23 am:
We don't have any problems with primary fatty alcohols, either "as is" or as trimethylsilyl derivatives.
-------------------------------------------------------------------------------------------------------
By Ron on Monday, June 21, 2004 - 06:22 am:
In addition to making sure the column oven equilibration time is long enough and that the GC is not injecting before the oven is ready, check for leaks at the inlet, especially if you have variation in area counts of standards as well as retention time variations.
-------------------------------------------------------------------------------------------------------
By meat head on Saturday, July 10, 2004 - 10:49 am:
clean your spliter
-------------------------------------------------------------------------------------------------------
By jay on Friday, July 16, 2004 - 04:17 am:
I think leak at injector side
-------------------------------------------------------------------------------------------------------
By ced on Monday, July 19, 2004 - 02:21 am:
Check and change your septum...
Check your column connection at the injector port.
-------------------------------------------------------------------------------------------------------
By Chromatographer1 on Monday, July 19, 2004 - 05:26 am:
Another problem may lie in underivitized alcohols is the peak assymetry with overloaded peaks. The retention time will change with concentration. Since you noted the area counts vary greatly, you may have 'American Motors' logo shaped peaks (I know that statement dates me). In this case, a picture would be worth a million words, but no chromatogram to review is our case sadly. Good luck.
-------------------------------------------------------------------------------------------------------
By GPS on Monday, July 19, 2004 - 09:32 am:
When we mean the retention time is consistent, do we consider till the third decimal (*.***) ?
