Use the Targeted Inclusion Isotopic Ratio filter, which triggers the next data-dependent scan only if the system detects an ion with the isotopic mass difference and ratio from the list. You can also import the settings from (or export them to) a .cvs, a .txt, or an .xml file.

 

The following table describes the parameters in the Targeted Isotopic Ratio Properties pane.

Parameter

Description

 

Mass List Table

Delta M

The mass difference (in Daltons) between the monoisotopic peak and the next isotopic peak.

Range: –2,000 to 2,000; default: 1.1

Expected Ratio

The isotopic intensity ratio.

Range: 0–10; default: 0.8

Compound

(Optional) Specify the name of the ion.

 

Ratio Tolerance (%)

Defines how close (as a percentage) an isotopic ratio must be to the expected ratio in the mass list to be considered the same ratio.

Range: 0.001–100; default: 5

IMPORTANT: The ratio tolerance is a percentage. For example, a ratio of 0.8 and a tolerance of 5 implies that the ratio must be within 0.8 ± 5/100 = 0.75 to 0.85 to be considered the same ratio as 0.8.

Mass Tolerance

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

  • 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 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 mass tolerance 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