Peak Overlap

[Thuypham]

Hi all,

I work at a GC 7890B/MSD 5977A Agilent
I use organochlorine pesticides standard (26 compound) with surrogate DDT 13C12 and internal standard Chrysene d12.

I have a few questions like this:
- The overlap between Heptachloro epoxide peak and Oxychlordane peak, can't separate. how to quantify the concentration of each compounds?
- With standard include 26 compounds, i just use a standard internal chrysene d12, is it okay?
- Difference: separate SIM groups (in External standard method) and SIM groups (in Internal standard method)?


Sorry, my English is very bad, hope everyone understand. 
Thank you very much.

[Steve Reimer]

For heptachlor epoxide use 353 and 81 m/z
For oxychlordane try 387 and 185
Test with individual standards to see how much interference you have.

There will be a small amount of 387 in your heptachlor but as long as you are not trying to quantitate a small amount of one in the presence of a large amount of the other you should be OK.

With the common chlorinated pesticide mixes it can be hard to find columns that separate all the components and they do have many ions in their mass spectrum.