Thermo Finnigan LTQ - Scan Power and Scan Modes; MS Scan Mode; MS;MS Scan Mode; Msn Scan Mode

Introduction
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______________________________________________________Scan Power and Scan Modes
_______________________ Finnigan LTQ Hardware Manual _____________________
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1.3 Scan Power and Scan Modes
Ions that are produced in the ion source are often referred to as parent ions.
These parent ions can be mass analyzed to produce a mass spectrum.
Alternatively, by varying the RF voltages of the mass analyzer, LTQ can first
eject all ions except for several selected parent ions, and then collide these
ions with helium that is present in the mass analyzer. This helium is known as
buffer gas. The collisions of the selected precursor ions with the helium can
cause them to fragment into product ions. The product ions can be mass
analyzed.
The number of stages of mass analysis is represented as MS
n
where n is the
scan power. (Each stage of mass analysis includes an ion selection step.) LTQ
supports scan powers of n =1 and n = 10. The higher the scan power, the
more structural information is obtained about the analyte.
The scan powers supported by LTQ in its standard configuration are as
follows:
• MS scan mode (n =1)
• MS/MS scan mode (n =2)
• MS
n
scan mode (n = 3 to 10)
MS Scan Mode
The MS or mass spectrometry scan mode corresponds to a single stage of
mass analysis (that is, a scan power of n = 1). The MS scan mode involves
only parent ions, and no fragmentation of the parent ions takes place. The MS
scan mode can be a full scan experiment or a selected ion monitoring (SIM)
experiment (see below).
MS/MS Scan Mode
The MS/MS scan corresponds to two stages of mass analysis (n = 2 scan
power). In an MS/MS scan, parent ions are fragmented into product ions. An
MS/MS scan can be a full scan experiment or a selected reaction monitoring
(SRM) experiment (see below).
MS
n
Scan Mode
An MS
n
scan involves three to ten stages of mass analysis (n = 3 to n = 10
scan power). [However, the term can also be applied to one stage of mass
analysis (with n = 1) or to two stages of mass analysis (with n = 2).] An MS
n
scan can be either a full scan experiment or a consecutive reaction monitoring
(CRM) experiment (see below).