DDT by GCMSD is not linear?

Chromatography Forum: GC Archives: DDT by GCMSD is not linear?
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Kelvin Law on Thursday, September 11, 2003 - 06:34 pm:

We try to use GC-MSD (5973) in determination of organochlorine pesticde. There are no problem to HCH, HCB, chlordane or aldrin, DDE etc. Only DDT (both o,p-DDT and p,p-DDT) give curve upward response! RSD of response factor >20. Is it relate to repeller voltage or ion source temperature?


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Thursday, September 11, 2003 - 10:52 pm:

Usually the problems with OC-pesticides are related to the injection port. We use double-tapered liners plus gold plated injector bottom seals. With 5973you could also use pulsed pressure injection (if using splitless injection.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Kelvin on Friday, September 12, 2003 - 04:03 am:

The problem is not come from injector or on line column degration.
There is no problem to ECD in the same GC.
We use pulse splitless injection for a long time.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Stanislaw on Tuesday, September 16, 2003 - 06:27 am:

I analyse pesticides on HP 5971 GC/MS. Some pesticides produce nonlinear response, then I use quadratic calibration fit instead of linear. However,I have never experienced this problem with DDT. There is another problem instead. DDT and endrin decompose in active injection port, for that you must replace liner frequently.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Wednesday, January 28, 2004 - 03:47 am:

The ion source of 5973N is not "inert" enough!
For some active compound, it will decompose over the ion source.
Purchase agilent new design inert ion source may overcome the problem.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Saturday, May 29, 2004 - 06:02 am:

I am Vivek K. Gaur
I would like to know the separation of HCH and its isomer in GDMSD system either they have the same molucular weight.
I want to know either structure is responsible for that.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Thursday, June 10, 2004 - 08:12 am:

HCH isomers cannot be separated by MS, but GC-column. The separation of beta-HCH and gamma HCH is not good for HP-5ms column. HP-35MS column can separate alpha, beta, delta and gamma HCH and it is low beeding for MS analysis.


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