|Three options are currently implemented: Quantitation..., Arithmetics...
and Isotopic Patterns.
At least this is what the MassLib user finds on the respective menu
MassLib features more instead: Background corrections and the automatic
determination of unique ions are so frequently used they got implemented
as permanent buttons (BCorrect) or as a standard tool (Unique Ions and
Check) also appearing on Curve and Spectra popup menues. Peakfinder,
a tool allowing semiautomatic SISCOM searches is of a similar nature (tool
button, Curve menu entry).
GC/MS Background Correction: The most important and also most frequently
used arithmetic feature of MassLib is its automatic background correction
for GC/MS (neither broad peaks nor very low intensities nor non-GC runs
such as solid probe work are covered by this practical tool). BCorrect
is very conservative and does corrections on each mass trace individually
(it is no spectrum subtract algorithm).
Unique Ions: For all kinds of mixture corrections and quantitative
considerations concerning overlapping peaks, unique ion traces (mass traces
of ions unique to only one of the overlapping components) are essential.
MassLib finds them itself (tools Unique Ions and Check). The tool is insensitive
towards GC/MS column bleed fluctuations. How important this tool is to
find components buried in the background or in coelutions, or hidden in
flat TIC-controlled solid probe analyses is evident.
Peakfinder: Working on a selection of e.g. a GC/MS run it finds
the most important spectra itself for further processing such as SISCOM
searches. Once initiated the MassLib user is set free for a coffee break
or for more demanding tasks. Output redirection to the printer allows him
to look over the results very quickly as the structure plots on the output
will give him the clues where to continue work interactively. Output may
contain a hitlist of spectra with structures as well as the unique ion
Check described above.
Arithmetics: Even if background corrections are mostly done on each
spectrum it is sometimes desirable to add spectra first und then subtract
some summed up background. MassLib facilitates the operation by filling
in the selected spectra automatically in the arithmetics window and by
offering Add Spectra on a selection popup menu. Additions and subtractions
may either be done by mean value or by an explicitly given percentage.
Spectrum corrections (to account for overlaps) is another important
issue. Rarely the arithmetics window is used for this as the spectrum popup
menu offers both, automatic corrections and corrections by zeroing unique
ions (defined simply by positionning the mouse on the unique ionís mass
Quantitation: MassLib does not yet provide quantitation for GC/MS
work. An according module is planned however. Currently available and implemented
into the calculations menu is a tool allowing to fit a given set of spectra
(such as a part of a hitlist) into a spectrum. The goal is to find the
percentage of each component in a mixture. Similarly, using unique ion
traces as the representatives of overlapping components, a fit of the unique
ions curves into the RIC (Reconstructed total Ion Chromatogram) allows
an estimation of the percentage each component contained in a mixture GC
Isotopic Patterns: A flexible module does not just allow to calculate
simple isotopic patterns but to generate also complex isotopic clusters
(created by e.g. variable amounts of hydrogen loss).
The feature may also be used (using the Compare spectrum display) to check
isotopic patterns in unknowns.