Precursor Mass Tolerance ppm to Dalton Window Converter
Convert a symmetric precursor ppm tolerance to an m/z window; no mass-calibration or identification inference.
Description
Convert a symmetric precursor ppm tolerance to an m/z window; no mass-calibration or identification inference.
A parts-per-million mass tolerance scales with the reference m/z value. Converting it to an absolute half-width makes the symmetric search window explicit.
When to use this tool
Convert a symmetric precursor ppm tolerance to an m/z window; no mass-calibration or identification inference.
- Prepare the supplied precursorMz, tolerancePpm fields for this operation.
- Compare the complete example with the representation used by your own input before carrying the result into another step.
How to use the tool and how it works
- Enter precursorMz, tolerancePpm. Use the exact text syntax, units and index conventions explained below.
- Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
- Read result.halfWidthDa, result.lowerMz, result.upperMz. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Require positive precursorMz and nonnegative tolerancePpm. Compute halfWidthDa=precursorMz*tolerancePpm/1,000,000, then return precursorMz minus/plus that width as lowerMz/upperMz.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| precursorMz | precursor mz. | Finite number; greater than zero |
| tolerancePpm | tolerance ppm. | Finite number; zero or greater |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.halfWidthDa | The half width da value under the stated formula or text convention. |
| result.lowerMz | The lower mz value under the stated formula or text convention. |
| result.upperMz | The upper mz value under the stated formula or text convention. |
{
"input": {
"precursorMz": 500,
"tolerancePpm": 10
},
"output": {
"result": {
"halfWidthDa": 0.005,
"lowerMz": 499.995,
"upperMz": 500.005
}
}
}Limitations and assumptions
- The bounds remain in the supplied m/z coordinate, despite the halfWidthDa field name. The tool does not convert to neutral molecular mass, model calibration error or clamp a negative lower bound.
- Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
- Ordinary string lists have at most 128 entries of at most 128 code units each; numeric lists and matrices have separate bounded size checks. Nonfinite results and excessively large serialized outputs are rejected.
- Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.
Alternative or Complementary methods
Use compatible mass, charge and sequence conventions when combining these operations. Inspect experimental spectra or quantitative controls separately; sequence features and theoretical mass arithmetic are not peptide identification or biological interpretation.
References
Similar or alternative tools
- fragment tolerance ppm
A ppm tolerance expresses a mass-width allowance relative to a reference m/z.
- charge from precursor mz
Precursor-charge inference searches positive integer charges for the theoretical m/z nearest an observation.