Introduction
Experiment Types
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______________________ Finnigan LTQ Hardware Manual _______________________
Data-Dependent Experiments
A Data-Dependent experiment is best used for the qualitative analysis of
unknown compounds for structure elucidation or confirmation. The LTQ uses
the information in a Data-Dependent experiment to make decisions about the
next step of the experiment automatically — without input from a user.
Instrument Setup contains the Instrument Method templates that you need to
get started with Data-Dependent experiments.
A Data-Dependent experiment produces a great deal of data from a single
sample analysis. You can run a Data-Dependent experiment even if you know
very little about your sample, and even if you are unfamiliar with the variables
of mass spectroscopy. In a Data-Dependent experiment, you can specify
parent ions for fragmentation or you can let the LTQ automatically select the
ions for fragmentation. The LTQ can collect the structural information for
every parent ion in the sample automatically, even if the sample is a mixture
of compounds.
A Data-Dependent experiment requires minimal input from a user about how
the experiment should best proceed. The user specifies that one or more scan
events of an experiment segment are to be run as Data-Dependent. Then, the
LTQ collects MS/MS or MS
n
data and makes decisions about what the next
step in the experiment should be to collect even more data. For example, in a
Data-Dependent Triple Play experiment for a mixture of compounds, the LTQ
can decide which parent ion to isolate, the charge state of the parent ion, and
the molecular weight of the compound.
Ion Mapping experiments can be Data-Dependent. (The Total Ion Map,
Neutral Loss Ion Map, and Parent Ion Map experiments are not
Data-Dependent.) The Data-Dependent Zoom Map experiment collects
ZoomScan data on every scan interval in a specified mass range.
Ion Tree experiments are types of Data-Dependent experiments. These
experiments provide methods for automatically interpreting MS
n
data and
arranging the data in formats that are easy to manipulate.
You can approach the setup of Data-Dependent experiments in either of two
ways:
•
If you have some idea of the parent ion, or if you expect a certain kind of
parent, you can set up a list of possible parent ions. Then, when one of the
parent ions you specified is detected, you can acquire product spectra and
analyze the information. Conversely, you can also set up a list of ions that
you do not want to be selected for fragmentation.
•
If you have little information about your compound, you can set up the
parameters of a Data-Dependent experiment so that if the intensity of the
ion signal is above a specified threshold, the LTQ generates product
spectra. Later, you decide if the information is useful. Parameters that you
might specify, for example, include threshold values for the intensity of
the MS or MS
n
ion signal. Whatever threshold values you choose should
accomplish the isolation of your parent ions of interest.