The Agilent 6540 UHD Q-TOF produces more accurate isotope ratios than Thermo LTQ Orbitrap XL
This document presents a technical comparison between the Agilent 6540 UHD Accurate-Mass Q-TOF LC/MS system and the Thermo Scientific LTO Orbitrap XL. It highlights that while accurate-mass measurements are useful, accurate isotope ratios are essential for reducing plausible molecular formulas and increasing confidence in compound identification. The text argues that accurate relative isotope abundances are critical for identifying isotopically-labeled proteins and peptides.
A benchmarking study described in the document reveals that the Thermo Scientific LTO Orbitrap XL exhibits large errors in relative isotope abundances, with some ratios being less than 20% of the theoretical value at high resolution. In contrast, the Agilent 6540 UHD O-TOF demonstrates a consistently low relative isotope abundance (RIA) error of about 5% across different acquisition rates. The document concludes that the combination of isotopic fidelity and Agilent's Molecular Formula Generator (MFG) software makes the 6540 UHD a better choice for unknown compound identification.
The system shows a consistently low relative isotope abundance (RIA) error of about 5%.
The software considers the accurate mass of the parent ion, isotope abundance distribution, and mass spacing between isotope peaks.
At a resolution of R=100,000, some observed isotope ratios were less than 20% of the theoretical value.