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Accurate Mass Measurements
Accurate mass measurements are used to determine the elemental composition
of the ion of interest. The m/z value is determined under high resolution
conditions to an accuracy within the low parts per million region. The
higher the m/z value, the more difficult the accurate mass measurement becomes.
Because of this difficulty, the MS Facility sets an upper limit of 1,000 u
for accurate mass measurements. Above this limit, a good match between theoretically
expected and experimentally measured isotope patterns is suggested as an
acceptable alternative.
Learn more about exact
mass measurements from JEOL.
SIS isotope patterns and exact
mass calculator
Gas Chromotography/Mass Spectrometry (GC/MS)
GCMS is the combination of a powerful separation technique, GC, with
a versatile detector,MS. Components of a mixture are separated by the GC
and mass spectra are recorded. EI and CI modes
of ionization are avialable for GCMS.
GCMS in the MS Facility
Liquid Chromotography/Mass Spectrometry (LC/MS)
Like GCMS, LCMS combines a powerful separation technique with a versatile
detector. Mixtures of thermally labile samples are separated with a LC
and a mass spectrum of each component is obtained. Two LCMS interfaces are available
with the Micromass Quattro LC: Electrospray ionization (ESI), and
Atmospheric Pressure Chemical Ionization(APCI) The JEOL AX505HA is also
equipped with a Frit-FAB interface.
LCMS in the MS Facility
MS/MS Experiments
MS/MS experiments are useful for structure elucidation. Three
types of MS/MS experiments available in the MS Facility are described below.
- Product Ion Scans: This experiment can be used to determine
the fragment ions which arise from a selected precursor ion. (Also known
as Daughter ion scans.)
- Precursor Ion Scans: This experiment can be used to determine
the precursor ions which give rise to a selected fragment ion. (Also known
as parent ion scans.)
- Constant Neutral Loss Scans: This experiment can be used to
determine which ions undergo the loss of a given neutral fragment.
Linked Scan Experiments
Linked Scan experiments are available on the JEOL AX505HA for structure elucidation. Three
types of linked scan experiments available in the MS Facility are described above under MS/MS experiments.
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