Table 6-10 IDA Criteria
Description
Label
IDA criteria are filters that are applied to the survey experiment, that is, TOFMS experiments.
Only the ions meet IDA criteria are triggered for MS/MS experiments. In each application
workflow, the appropriate IDA criteria are selected and shown on UI. Or, the user can select
all workflow to choose desire criteria.
IDA Criteria
Specify the number of TOF MSMS experiments that are performed per cycle. If there are
fewer candidate ions than the maximum candidate ions entered, then the time spent on
MS/MS is distributed among the candidate ions. That is, the total cycle time is held relatively
constant throughout the acquisition. All of the returned TOF MSMS spectra are normalized
to cps. In the software, users can add up to 100 TOF MSMS experiments per cycle.
Maximum
candidate ions
Select to prioritize the ions that are increasing in intensity in the TOF MS spectra, and then
trigger for MS/MS acquisition before the intensity starts to decrease. This filter removes the
constant background ions from the candidate list and triggers ions that are minor but are
increasing in intensity. The ions could be triggered multiple times when the signal-to-noise
ratio is high. The dynamic background subtract filter can be used with the other standard
filters in the IDA criteria section.
Dynamic
background
subtraction
Specify the minimum intensity (ion counts per second ) of the candidate ions for the TOF
MSMS experiment.
Intensity threshold
exceeds
Select an option for ignoring previous candidate ions:
• For (sec):
After the candidate ion has been selected for TOF MSMS experiment, do not consider it
for MS/MS for the next X seconds. It is recommended that this value to be set to half
the LC peak width to ensure the candidate ion can be triggered at the peak apex.
• After _ occurrences:
In combination with For X seconds: Allows the candidate ion to be selected for MS/MS
for Y times in the following cycles during X seconds before being excluded from the
candidate list.
Note:
Dynamic exclusion routine uses MW (not the
m/z
ratio). Candidate ions with
the same MW (within the mass tolerance) but difference charge states will be considered
to be the same candidate. The charge state that is the most intense survives on the
candidate list if the number of repeats has not been met. If the candidate ion has been
selected for MSMS once, and do not want to be triggered any more, in For (Sec) field,
type in the method duration time as second.
Exclude former
candidate ions
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Operating Instructions—Software
