Method of standard additions by Headspace

Chromatography Forum: GC Archives: Method of standard additions by Headspace
Top of pagePrevious messageNext messageBottom of pageLink to this message  By ana on Monday, December 22, 2003 - 05:15 am:

I am trying to develop a method for the Residual solvents determination in pharmaceutical substances using the method of standard additions MSA by HS.This method is required by European Pharmacopoeia. I have problems with MSA. I added 10, 20, 30, 40, 50 and 60 ppm of the analyte to the sample however the result was negative concentration.
Has anybody experience with the method of standard additions. Please help as soon as possible and give as much detail.
Thanks


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Laurent on Tuesday, December 23, 2003 - 01:49 am:

I dont really know this method but it sounds like you have too small analyte concentrations.
While making you calibration curve do you force the "zero" Point ?
If not you will perhaps have some negative deviation for the small concentrations that could explain this "negative concentration".


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, December 23, 2003 - 12:21 pm:

Are you getting increasing peak areas as you add increased concentrations of your standard? If so, then your chromatography is okay. Laurent may be right about something amiss in your standard curve calculation.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Wednesday, January 21, 2004 - 12:48 am:

hai ana,
In general, standard addition method is applicable only when the analyte of your sample contains lesser than its LOQ AND LOD limits. As you would like to add less than 100 pppm i suggest to do the SPLITLESS INJECTION.
good luck


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Wednesday, January 21, 2004 - 09:00 am:

ana,
you should give some more details about your EP method.Is it solution / headspace or solid / headspace analysis? Is it possible to simulate the matrix by solvent-free matrix? I am fearing you have some re-adsorption effects.
PETER


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