Chromatography Forum

Hello,

I have run the 37 FAME Mix from Supelco on a Thermo GC-MS, using Rtx5-sil column, and wish to generate/ assign the Retention Indices to the FAMES using AMDIS or so ? How is it done to generate the .CAL file (from the .netCDF/ .raw files from Thermo with me!) so that I can compare and identify all my compounds run using same conditions (full-scan mode!).

Do I have to (a) search NIST first to assign RIs to these compounds based on their known RIs from similar columns such as DB5, HP5 etc, or
(b) I have to calculate them de novo to be able to identity and assign their RI, and use these values for "other compound" identifications ?, or,
(c) should I use the Hydrocarbon RI .CAL File inbuilt in AMDIS-NIST Library to first generate the RI for these FAMES, first ? But that is not comparable, right ?

Looking forward to your kind advice,

Thanks and regards,
Biswa

Hello Biswa,

I suggest buying a set of hydrocarbons, that way there can be no doubt as to the RT of the hydrocarbons
as a ramped temperature programme will affect the calculations.
Sigma has some 9452-U SUPELCO C7 - C40 Saturated Alkane Mixture, or 49451-U SUPELCO
C7 - C30 Saturated Alkanes. Use the same GCMS method as the FAMEs, that way you can not get into trouble about using predicted RIs as from NIST etc..., as you know that C7 = 700, C8 = 800, ...,C30 =3000

For a text mixture, you could mix the two to make a only a single vial to inject, saving the time of injecting an extra vial, I think both are made up in Hexane?

As you will have the Alkane Mixture, making the .CSL and and thus the .CAL will be very easy to do via AMDIS,
as you could possibly make an error if you attempted to manually enter in values.
Plus as you will documenting the process, screen capture and training will be easy

Hope this helps
Alex