In GC-MS or LC-MS/MS confirmation, what is the purpose of retention times?

• A. They determine the mass-to-charge ratio of ions.
• B. Retention times help confirm identity of analytes and must match reference standards within specified windows.
• C. They measure the concentration of analytes directly.
• D. They indicate the sample's pH.

Answer: (B)

Retention times are used as an additional identifier in GC-MS and LC-MS/MS. After the sample is separated, each compound elutes from the column at a characteristic time under defined method conditions. By comparing the observed retention time to the reference retention time for a known standard and confirming it within an allowed window, you strengthen the identification of the analyte. This works alongside the mass spectral data to prevent misidentification from compounds with similar spectra and to account for slight run-to-run variability in chromatography. Retention time itself isn’t used to determine mass-to-charge ratio, nor to quantify concentration directly, and it doesn’t indicate sample pH.