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

Area of Science:

• Analytical Chemistry
• Spectrometry

Background:

• Nominal mass spectra derived from the same NetCDF file vary across different gas chromatography/mass spectrometry (GC/MS) software.
• Discrepancies arise from distinct algorithms employed for rounding floating-point m/z values to integers.

Purpose of the Study:

• To investigate the distribution of fractional parts of accurate m/z values.
• To identify algorithms yielding more robust results for nominal mass spectra generation.
• To propose a procedure minimizing rounding errors in m/z values.

Main Methods:

• Analysis of nominal mass spectra generated by multiple GC/MS software packages (AMDIS, ChemStation, ChromaTOF, MS Search, OpenChrom).
• Estimation of fractional m/z value distribution using PubChem and NIST databases.
• Development and validation of a novel rounding procedure.

Main Results:

• Identified significant variations in nominal mass spectra due to differing m/z rounding algorithms.
• Determined the distribution of fractional parts of accurate m/z values.
• Proposed a binning method summing intensities in the range [MZ-0.38; MZ+0.62] to improve nominal m/z value accuracy.

Conclusions:

• The choice of GC/MS software significantly impacts nominal mass spectra quality due to rounding variations.
• The proposed method of summing intensities within a defined m/z bin enhances the robustness of nominal mass spectra.
• This approach mitigates random errors associated with integer m/z value conversion.