Introduction
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_______________________________________________________________ Experiment Types
_______________________ Finnigan LTQ Hardware Manual _____________________
1-21
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You can find useful structural information about your compound
automatically with the simplest Data-Dependent experiment, Data-Dependent
MS/MS. You specify the MS scan range, and you do not even need to specify
a parent ion. The LTQ can then collect full scan MS data, pick the most
intense parent ion in the spectrum, and fragment the ion to generate product
ions.
A Data-Dependent Triple-Play experiment is the same as Data-Dependent
MS/MS, but includes the identification of the charge state of the parent with
the LTQ ZoomScan feature. A Data-Dependent Triple-Play experiment
collects full scan MS data, and then uses ZoomScan to determine the charge
state of the parent ion and calculate the molecular weight. The parent ion is
then fragmented into product ions (MS/MS). For example, if the LTQ
determines a charge state equal to 2, and if the mass-to-charge ratio of the
parent ion is m/z 500, then the mass-to-charge ratios of the product ions can be
up to m/z 1000 (or 2
×
500).
You can use a Data-Dependent experiment (from templates in Instrument
Setup) to do the following:
•
Identify low-level impurities in high-purity compounds (Data-Dependent
MS/MS)
•
Identify metabolites in a complex mixture (Chromatographic Separation
with Data-Dependent MS/MS)
•
Build a custom library of composite MS
n
spectra (Ion Tree)
You can use a Data-Dependent MS
n
experiment to identify process impurities.
In the quality assurance process for aspirin, for example, the LTQ can identify
impurities of 0.1%.
A Data-Dependent MS/MS experiment of a complex mixture of drug
metabolites can provide highly specific structural information. Characteristic
masses along the metabolic pathways of a drug, for example, can produce
MS/MS spectra that are specific to the structure of the drug. These spectra are
essential in metabolite identification.
A Data-Dependent experiment can produce a composite spectrum of, for
example, MS
2
, MS
3
, and MS
4
data. The LTQ can store the MS
n
fingerprint
data in a custom MS
n
library spectrum. The data is valuable for use in process
control, quality assurance, or research.
Ion Mapping Experiments
An Ion Mapping experiment is best used to get full structural characterization
of unknown molecules in complex mixtures. In an Ion Mapping experiment,
you can get product ion scans on every parent ion over a specified mass range.
An Ion Mapping experiment can help to identify automatically which parent
ions were fragmented to yield a specified product ion. The experiment “maps”
one or more parent ions by using the information from product ion scans.