Question about RI vs RT usage in MS-DIAL GC-MS identification (DB-WAX vs DB-5 libraries)

[Pamou14160]

Hi,

I have a question regarding the Identification section in Setting Project Parameters in MS-DIAL5.

I understand that identification results can be expressed using either Retention Index (RI) or Retention Time (RT), depending on whether an alkane mixture has been analyzed. I also understand that RI values can contribute to compound identification in addition to EI spectral matching when “Use retention information for scoring/filtering” is enabled — provided RI values are available in the spectral library.

The public MS-DIAL GC-MS libraries are based on DB-5 type columns. However, my GC-MS method uses a DB-WAX column, meaning RI values from the library are not directly comparable.
In this case, I assume:
• I can still use the library for EI spectral matching
• But RI should not be used for identification scoring or filtering
• Therefore:
• I should keep RI selected, but set a very large RI tolerance (e.g., 10,000) so RI is effectively ignored
• I should disable “Use retention information for scoring” and “Use retention information for filtering”
Is this the correct approach?

If alkanes are not available, I may use Retention Time (RT) instead of RI.
However, RT strongly depends on:
• Column type
• Temperature program
• Instrument configuration
So I assume RT should not be used for identification filtering either.
Therefore, I presume:
• RT tolerance should be set high (e.g., ≥100)
• Retention-based scoring/filtering should remain disabled
• Identification should rely only on EI spectral similarity.
Is this also correct?

When using NIST libraries in MSP format, I see that Retention Index values exist for different column types.
Is there a way in MS-DIAL to:
• Specify which column type was used (e.g., DB-5 vs DB-WAX)?
• Select or prioritize the matching RI set from the library?
• Or otherwise make proper use of column-specific RI information for compound identification?

Thanks for your help!