A general procedure for rounding m/z values in low-resolution mass spectra

Mikhail Khrisanfov, Andrey Samokhin
Rapid Comm in Mass Spec Volume36, Issue11 2022.
Science Published: (Mar/2022)
DOI: https://doi.org/10.1002/rcm.9294

It was revealed that nominal mass spectra extracted from the same NetCDF file using different gas chromatography/mass spectrometry (GC/MS) software products are not identical. This phenomenon is caused by differences in algorithms used for rounding floating-point m/z values to integers. It was found that all programs under consideration (AMDIS, ChemStation, ChromaTOF, MS Search, OpenChrom) use different procedures. It is necessary to know how fractional parts of accurate m/z values of ions are distributed to determine which algorithm yields more robust results. We estimated the respective distribution using two databases (PubChem and NIST). As a result, we came up with a procedure that minimizes the influence of random errors on rounding to integer m/zvalues. The procedure we suggest is to sum intensities of all floating-point m/z values in a bin [MZ − 0.38; MZ + 0.62] and assign MZ as a nominal m/z value, where MZ is an integer m/zvalue.

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