Graph-Based Method for Calibration of High-Resolution Mass Spectra of Natural Organic Matter

Qiong Pan,^*Chen He, and Quan Shi^*

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, People’s Republic of China; Department of Chemical Engineering, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, United Kingdom

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, People’s Republic of China

^*Corresponding Authors:Qiong Pan − Email: panqiong_cup@outlook.com ;Quan Shi −  Email: sq@cup.edu.cn

DOI:10.1021/acs.analchem.3c05423

Keywords: Calibration; Extraction; Fossil Fuels; Mass Spectrometry; Natural Organic; Natural Organic Matter

Abstract: Inaccuracies in iondetectionandsignal processing can undermine confidence in the molecular formula assignment of high-resolution mass spectrometry, which relies on precise matching of  the mass-to-charge ratio (m/z). This study proposes a novel graph-based spectra calibration method, MSCMcalib, which implements  coordinate transformation and pattern detection. MSCMcalib maps  uncalibrated m/z data onto amodified 2D massdefectplot, facilitating  the automatic calibration of detected lines, i.e., the calibration of  uncalibrated peaks aligned with these lines. The “propagation” method is subsequently employed to accurately and automatically calibrate 605 m/z values across multiple lines, encompassing 98% of  the m/z range. The calibrated m/z values divide the m/z range of the spectrum into multiple subintervals, with each subinterval undergoing a process of “scaling” calibration. The utilization of narrower partitions effectively mitigates divergence issues at both ends that arise from the polynomial fitting of errors against m/z. The effectiveness of MSCMcalib is validated through the calibration of SRFA data with m/z error ranges spanning from −10 to −6 ppm, resulting inanadditional assignment of 11%−30% more molecular formulas compared to the quadratic fitting calibration.