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Table 6-10 IDA Criteria (continued)
Description
Label
Select the check box to use the Mass Defect Filter criteria. Click the link to open the IDA:
Mass Defect Filter dialog and edit the criteria.
MS/MS is triggered on any ion that meets the specified mass defect criteria. The IDA algorithm
converts the ion to its molecular weight and then compares the molecular weight to the
mass defect criteria. The mass defect filter can be applied to filter all of the ions that fall
outside of the expected molecular weight range, as well as those ions that are within the
expected molecular weight range but exceed the expected mass defect range
Mass defect ( mDa ) = ABS ( mono mass - nominal mass )
• Chemical formula: Type the molecular formula of the representative compound of interest.
Multiple formulae can be entered to allow for real-time multiple mass defect filtering.
• MW ( Da ): The software generates the mono molecular weight of the chemical formula.
• MW tolerance (+/- Da ): When a formula is entered, the software automatically calculates
the associated molecular weight (MW).The MW tolerance (+/-Da) is the window centered
around the calculated MW. If a candidate ion has a mass defect that meets the mass
defect ± the mass defect tolerance, and falls within the window around the MW, then
it is considered for MS/MS.
• Mass defect ( Da ): Type the molecular formula and MW tolerance. The software calculates
the mass defect of the entered formula.
• Mass defect tolerance (mDa): Type the tolerance around the mass defect.
Use the mass defect filter with no other IDA criteria: Select the check box to use the mass
defect filter exclusively. MS/MS is performed only on candidate ions that have a mass defect
that falls within the given criteria. If this check box is not selected, then the candidate ions
that meet the mass defect criteria have a higher priority in the candidate list over other ions
that meet the rest of the IDA criteria specified, with the exception of the inclusion list.
Candidate ions satisfying the inclusion list will have the same priority as those satisfying
the mass defect criteria.
Mass Defect Filter
SCIEX X500 QTOF System
System User Guide
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RUO-IDV-05-2334-E
Operating Instructions—Software