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Decomposition of electron ionization mass spectra for space application using a Monte‐Carlo approach
Author(s) -
Gautier Thomas,
Serigano Joseph,
Bourgalais Jérémy,
Hörst Sarah M.,
Trainer Melissa G.
Publication year - 2020
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8684
Subject(s) - chemistry , monte carlo method , fragmentation (computing) , deconvolution , mass spectrum , spectral line , mass spectrometry , ionization , electron ionization , analytical chemistry (journal) , quadrupole mass analyzer , computational physics , ion , physics , statistics , chromatography , optics , quantum mechanics , mathematics , organic chemistry , computer science , operating system
Rationale Quadrupole mass spectrometers equipped with an electron ionization (EI) sources have been widely used in space exploration to investigate the composition of planetary surfaces and atmospheres. However, the complexity of the samples and the minimal calibration for the fragmentation of molecules in the ionization chambers have prevented the deconvolution of the majority of the mass spectra obtained at different targets, thus limiting the determination of the exact composition of the samples analyzed. We propose a Monte‐Carlo approach to solve this issue mathematically. Methods We decomposed simulated mass spectra of mixtures acquired with unit resolving power mass spectrometers and EI sources into the sum of the single components fragmentation patterns weighted by their relative concentration using interior‐point least‐square fitting. To fit compounds with poorly known fragmentation patterns, we used a Monte‐Carlo method to vary the intensity of individual fragment ions. We then decomposed the spectrum thousands of times to obtain a statistical distribution. Results By performing the deconvolution on a mixture of seven different molecules with interfering fragmentation patterns (H 2 O, O 2 , CH 4 , Ar, N 2 , C 2 H 4 , and C 2 H 6 ) we show that this approach retrieves the mixing ratio of the individual components more accurately than regular mass spectra decomposition methods that rely on fragmentation patterns from general databases. It also provides the probability density function for each species's mixing ratio. Conclusions By removing the solution degeneracy in the decomposition of mass spectra, the method described herein could significantly increase the scientific retrieval from archived space flight mass spectrometry data, where calibration of the ionization source is no longer an option.