Chromatography Forum

Hi All

we have just started using RI on our GC/MS systems to better identify unknowns.

I see that NIST MS Search does have an option for using RI to apply a penalty if it is a poor RI match and a good spectral match. This is exactly what we are doing by hand now and I would love for it to be automated to reduce errors made by lab techs.

However, how do I enter the C#/RT pairs into NIST MS Search after running an alkane ladder so that it can compute RIs based on the submitted spectra's retention times? I am at a loss.

Alternatively, how do I get an RI into the submitted spectrum? We usually search either from ChemStation, Xcalibur or MassHunter.

Thanks!

The single answerer to all of your questions is AMDIS. If you have the NIST MS Search Program, you have AMDIS. If you process your data files in AMDIS, when a spectrum is sent to MS Search it will have an associated Retention Index. The column type is specified in the MS Search Import settings.

If you are interested in a detailed procedure, send a request to massspec@nist.gov and reference this post.

This can also be done with MassHunter Unknowns Analysis. You need to enable the 'RT Match' function, and then specify an RI calibration file (a text file containing the RT and RI values for calibration standards run with the oven program that is going to be used in the method.)

Thank you very much to both of you for your helpful input. We’ll definitely try out both methods, depending on the make (and vintage) of the GCMS.