16 research outputs found
Characterization of the Spectral Accuracy of an Orbitrap Mass Analyzer Using Isotope Ratio Mass Spectrometry
Infrared
matrix-assisted laser desorption electrospray ionization
(IR-MALDESI) source coupled to the Q Exactive Plus has been extensively
used in untargeted mass spectrometry imaging (MSI) analyses of biological
tissue sections. Although the Orbitrap is a high-resolution and accurate-mass
(HRAM) mass analyzer, these attributes alone cannot be used for the
reliable identification of unknown analytes observed in complex biological
matrices. Spectral accuracy (SA) is the ability of the mass spectrometer
to accurately measure the isotopic distributions which, when used
with high mass measurement accuracy (MMA), can facilitate the elucidation
of a single elemental composition. To investigate the effects of different
ion populations on an Orbitrap’s SA and MMA, a solution of
caffeine, the tetrapeptide MRFA, and ultramark was analyzed using
a Q Exactive Plus across eight distinct automatic gain control (AGC)
targets. The same compounds from the same lot numbers were also individually
analyzed using isotope ratio mass spectrometry (IRMS) to accurately
determine the isotopic abundance of <sup>13</sup>C, <sup>15</sup>N,
and <sup>34</sup>S. We demonstrated that at optimum absolute ion abundances
the Orbitrap can be used to accurately count carbons, nitrogens, and
sulfurs in samples with varying masses. Additionally, absolute monoisotopic
ion abundances required for high SA were empirically determined by
using the expected (IRMS) and experimental (Orbitrap) isotopic distributions
to calculate the Pearson chi-square test. These thresholds for absolute
ion abundances can be used in untargeted MSI studies to shorten an
identification list by rapidly screening for isotopic distributions
whose absolute ion abundances are high enough to accurately estimate
the number of atoms
Characterization of the Spectral Accuracy of an Orbitrap Mass Analyzer Using Isotope Ratio Mass Spectrometry
Infrared
matrix-assisted laser desorption electrospray ionization
(IR-MALDESI) source coupled to the Q Exactive Plus has been extensively
used in untargeted mass spectrometry imaging (MSI) analyses of biological
tissue sections. Although the Orbitrap is a high-resolution and accurate-mass
(HRAM) mass analyzer, these attributes alone cannot be used for the
reliable identification of unknown analytes observed in complex biological
matrices. Spectral accuracy (SA) is the ability of the mass spectrometer
to accurately measure the isotopic distributions which, when used
with high mass measurement accuracy (MMA), can facilitate the elucidation
of a single elemental composition. To investigate the effects of different
ion populations on an Orbitrap’s SA and MMA, a solution of
caffeine, the tetrapeptide MRFA, and ultramark was analyzed using
a Q Exactive Plus across eight distinct automatic gain control (AGC)
targets. The same compounds from the same lot numbers were also individually
analyzed using isotope ratio mass spectrometry (IRMS) to accurately
determine the isotopic abundance of <sup>13</sup>C, <sup>15</sup>N,
and <sup>34</sup>S. We demonstrated that at optimum absolute ion abundances
the Orbitrap can be used to accurately count carbons, nitrogens, and
sulfurs in samples with varying masses. Additionally, absolute monoisotopic
ion abundances required for high SA were empirically determined by
using the expected (IRMS) and experimental (Orbitrap) isotopic distributions
to calculate the Pearson chi-square test. These thresholds for absolute
ion abundances can be used in untargeted MSI studies to shorten an
identification list by rapidly screening for isotopic distributions
whose absolute ion abundances are high enough to accurately estimate
the number of atoms