Small Difference in Signal Reponse on Multiple ECD's

Chromatography Forum: GC Archives: Small Difference in Signal Reponse on Multiple ECD's
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Monday, July 22, 2002 - 10:45 am:

I have 12 GC's with ECD's. I am seeing a 0.5-0.6 ppb difference between quantitative results for some of the instruments. All the GC's are using the same Method conditions, standards, and sample preparation. The instruments are all well maintained with background levels below 5 mV. All of the GC's are using headspace for sample introduction so the sample path way is very clean. All of my quantitative results are well within my control limits, but I am curious why I am seeing these small differences in quantitative results between some of the instruments.
Any ideas?


Top of pagePrevious messageNext messageBottom of pageLink to this message  By R. Plausinaitis on Tuesday, July 23, 2002 - 08:21 am:

Hi,

Short answer - since your GCs are not clones.

First, there might be slight (but within specification) differences in cell (and inlet, column ...) geometry, Ni source activity and things like that. Gas regulators and signal amplifiers perform differently.

Second thing is that you can't install liners, columns precisely same way on all instruments. These things also influence quantitation. Syringes used in GCs are not calibrated, etc., etc...


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