IonCat
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KatzLab Molecular Analytics

Easy Peasy Exact Mass Difference Calculator


Note for low mass deltas (e.g., when searching for N for CH delta) PPM probably wants to be high (like 50)

Elements

Min and max are editable. Changing mass does not reset rows. Use Reset defaults only when you want fresh element bounds.
Note: Min of 0 does MF generation. Below 0 allows substitutions.
Element Exact mass Min Max Remove
Defaults start at min 0 and use scaled max bounds. Set a negative min when you want to allow subtractions for an element.

Search notes

Default maximums are scaled from the current mass only when you click Reset defaults. Impossible formulas are filtered using halogen-aware DBE.
  • H max = about 20 per 100 Da
  • C max = about 10 per 100 Da
  • N and O max = about 4 per 100 Da
  • P and S max = about 2 per 100 Da
  • Na, K, Cl, Br, Mg, Ca, Fe, Zn max = 2 overall
  • DBE uses the halogen form: DBE = C − (H + X)/2 + N/2 + 1
  • H/C, O/C, and N/C are shown for the formula magnitude used in scoring.

Results

Additions and subtractions are shown as molecular formulas in CHNOPS-first order. Ratio chips are green for comfortable ranges, orange for borderline, and red for poor.
Enter a mass, review the element bounds, and click Go.