Dear Sarika,

I am sorry, I do not know what PM 10 means - I guess it might be a mixture of alkanoic acids. If the mixture is free of heptadecanoic acid, you can use it as an internal standard. 

Rastislav Solár.

I want to use heptadecanoic acid as external standard for 5 point calibration.and PM10 means particulate matter having diameter equal to and less then 10 um,present in ambient aerosol. 

Hi Sarika -

If you are using FID you might be able to use (C17) heptadecanoic acid to quantitate (C12)dodecanoic acid.  You would still need to verify whether it works or not, and that would require purchasing the individual target compounds any way.  I've posted link to US EPA Technical Assistance Document (TAD).  This has something that describes what you are trying to do specifically for air analysis, we use this technique to determine concentrations of Total Non-Methane Organic Compounds (TNMOC) in the lab.

Specifically please review section 2.3.1 regarding use of FID to quantitate alkanes. 

"The FID is the most widely used, universal GC detector. As a general observation, the FID provides good sensitivity and uniform response to n-alkanes based on the number of carbon atoms in the compound. For unsaturated, cyclic, or aromatic hydrocarbons, the FID response is less predictable."

http://www3.epa.gov/ttnamti1/files/ambient/pams/newtad.pdf

Hi Sarika,

I dont think so. I analysed monocarboxylic acids (C8 - C20) by GC-MS 5 years ago. I derivatized them into methyl esters by BF3/methanol and the peak area was different for different acids. The peak area of C16 was the biggest. However I dont have experiences with HPLC.

Rastislav.... PM10 means particles less than 10 micrometers. PM is Particulate Matter.