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| | | Forum Member
 
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Last Login: 6/18/2008 9:25:31 AM
Posts: 49, Visits: 95 |
| | We are performing PCBs in oil and are having difficulty recovering CCVs after running these particular samples. Any help would be appreciated. And if there exists a forum better suited for GC analysis questions, I'd be glad to know. Thanks. |
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| | | Supreme Being
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Last Login: Yesterday @ 3:10:37 PM
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| Is this the PCB analysis where you add concentrated sulfuric acid to the tube then cap and shake for the clean up step? It has been years since I did that analysis. If I am remembering correctly we had some trouble doing them and had to replace our inlet liners quite a bit with them. If you are using the pre-prepared liners try preparing your own. You can buy the inlet tubes then take glass wool and use the silanizing agent on it and the tubes directly. After silanizing just pour off the excess reagent then dry the tubes in a 105 degree oven overnight. When we had troubles with recovery it was almost always the liners that gave us problems. Like I said it was years ago, so if this isn't too helpful I am sorry, I thought I would take a crack at it since nobody else had yet.
Christopher Fair
R&D Chemist III
Hach Company
cfair@hach.com
www.boddoctor.com |
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| | | Forum Member
Group: Forum Members
Last Login: 9/9/2008 2:04:46 PM
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| | Chris is correct, the liner is almost always to blame for recovery problems. It is the first place I look. Are the recoveries consistently high, consistently low, or just inconsistent? If you repeat injection of the CCV does the recovery come back into range? This may indicate carryover from the previous sample affected the first CCV run. A drifting baseline can cause intergration problems which result's in an improperly integrated chromatogram. Try running a blank after the sample and before the CCV to allow the GC to cycle through its temperature program once. |
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| | | Supreme Being
Group: Forum Members
Last Login: Yesterday @ 3:10:37 PM
Posts: 166, Visits: 219 |
| Scap's recommendations are also good. To take running through the temperature program once without an injection one step further you can do a high temperature for some period between injections. This combined with solvent only can really go a long way to straightening out a bad baseline.
Christopher Fair
R&D Chemist III
Hach Company
cfair@hach.com
www.boddoctor.com |
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| | | Supreme Being
Group: Forum Members
Last Login: 9/3/2008 1:09:33 PM
Posts: 75, Visits: 114 |
| | Running a blank right before the ccv might raise a problem with some auditors and data validators because you are treating the ccv differently than your analytical samples. They probably would not have a problem with running a blank after every sample, but who wants to do that. Jack |
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