The Dynamic Exclusion filter prevents an ion from triggering additional data-dependent scans for a defined period after it has triggered a data-dependent scan. Dynamic exclusion is useful when the MS has acquired sufficient data for an ion or when the base peak corresponds to a contaminant or an ion of no interest.

When you use the Dynamic Exclusion filter and the MS performs a data-dependent scan on an ion, the system places that ion on the pre-exclusion list (a temporary reject mass list) for a user-specified period. If the MS performs a data-dependent scan on another ion, the system places that ion on the pre-exclusion list as well.

Use the "Exclude After n Times" parameter to specify the number of MS2 scans required before the system moves an ion to the exclusion list.

 

The following table describes the parameters in the Dynamic Exclusion Properties pane.

Parameter

Description

Exclude after n times

Allows each precursor to be selected up to "n" times before being adding to the dynamic exclusion list.

Range: 1–100; default: 1

Exclusion duration (s)

The amount of time the precursor remains on the exclusion list.

Range: 0–6,000; default: 60

Mass Tolerance

Defines how close a measured mass must be to the mass in the mass list to be considered the same mass.

Select from the following options:

  • ppm (default): The low and high values of the mass tolerance width in parts per million (ppm) of the reference mass. This option is appropriate for the Orbitrap mass analyzer because the peak width is proportional to the m/z.
  • You can specify the mass tolerance width as a percent value of the reference mass: first select the ppm option, and then type the desired values in the Low box and High box. The mass tolerance is expressed in parts per million (ppm). When you select ppm, the size of the window around the reference mass is proportional to the m/z of the reference mass.
  • m/z: The low and high values of the mass tolerance width in m/z. This option is appropriate for the ion trap mass analyzer because the peak width is constant.
  • You can specify the mass tolerance width in m/z: first select the m/z option, and then type the desired values in the Low box and High box. When you select m/z, the size of the window around the reference mass remains the same regardless of the m/z of the reference mass.

Low

The low side of the mass tolerance width window.

The low value defines how far below the reference mass the mass tolerance window starts on the low-mass side of the reference peak.

Range (ppm): 0.01–1,000,000; default: 10
Range (m/z): 0.01–100; default: 0.5

High

The high side of the exclusion mass width window.

The high value defines how far above the reference mass the mass tolerance window extends on the high-mass side of the reference peak.

Range (ppm): 0.01–1,000,000; default: 10
Range (m/z): 0.01–100; default: 0.5

Exclude Isotopes

Excludes the ion cluster isotopes from the dynamic exclusion list.

When Dynamic Exclusion is used with MIPS, this setting must be selected.

Default: Selected

By default, the Excludes Isotopes checkbox excludes all isotopes that have intensities that are greater than 40% of the base peak of the isotopic envelope.

This threshold can be modified in the Tune diagnostics.

NOTE: When combined with a MIPS filter, the exclude isotopes feature is enabled.

Exclude Within Cycle

Use this feature to have each m/z added to the exclusion list immediately after it is first analyzed. This will exclude it from other data-dependent scans that it would have qualified for in the same cycle.