Scan Types; Full Scan; Selected Ion Monitoring - Thermo Scientific TSQ Series Hardware Manual

Scan Types

TSQ systems can be operated with a variety of scan types. The most common scan types are as
follows:
•

Full Scan

•

Selected Ion Monitoring

• Selected Reaction Monitoring
• AutoSIM
Full Scan
The full-scan scan type provides a full mass spectrum of each analyte. With full scan, the scanning
mass analyzer is scanned from the first mass to the last mass, without interruption, in a given scan
time.
Full-scan experiments are used to determine or confirm the identity of unknown compounds or
the identity of each component in a mixture of unknown compounds. (Generally, a full mass
spectrum is needed to determine the identity of an unknown compound.)
The full-scan scan type gives you more information about an analyte than does SIM, but a full scan
does not yield the sensitivity that the other two scan types can achieve. With full scan, you spend
less time monitoring the signal for each ion than you do in SIM or SRM. Full scan provides greater
information but lower sensitivity than the other two scan types.
To use the SIM or SRM, you need to know what ions or reactions you are looking for before you
can perform an experiment with these scan types. Thus, you might use a full scan for SIM to
determine the identity of an analyte and to obtain its mass spectrum and a full scan for SRM to
determine the mass spectrum and product mass spectra for parent ions of interest. Then, you
might use SIM or SRM to do routine quantitative analysis of the compound.
Selected Ion Monitoring
Selected ion monitoring (SIM) monitors a particular ion or set of ions. SIM experiments are useful
in detecting small quantities of a target compound in a complex mixture when you know the mass
spectrum of the target compound. Thus, SIM is useful in trace analysis and in the rapid screening
of a large number of samples for a target compound.
Because SIM monitors only a few ions, it can provide lower detection limits and greater speed than
the full-scan modes. SIM achieves lower detection limits because more time is spent monitoring
significant ions that are known to occur in the mass spectrum of the target analyte. SIM can
achieve greater speed because it monitors only a few ions of interest; SIM does not monitor regions
of the spectrum that are empty or have no ions of interest.
SIM can improve the detection limit and decrease analysis time, but it can also reduce specificity.
Because SIM monitors only specific ions, any compound that fragments to produce those ions will
appear to be the target compound. The result can be a false positive.
Thermo Scientific
(SIM)
(SRM)
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Introduction
Scan Types
TSQ Series Hardware Manual 9