Comprehensive Lists of Internal Calibrants for Ultrahigh-Resolution Mass Spectrometry Analysis of Crude Oil and Natural Organic Matter and Their Preparation Recipes

In this work, comprehensive lists of internal calibrants for accurate mass determination of molecules in crude oils, natural organic matter, and soil as well as their preparation recipes are presented. The lists include various sets of chemicals for positive- and negative-ion mode electrospray ionization, atmospheric pressure chemical ionization, atmospheric pressure photoionization, and laser desorption ionization. The chemicals were chosen based on their solvent compatibility, ionization efficiency, and accessibility. The sample preparation process was optimized for each ionization method and type of sample. The lists include detailed information on preparation solvent, concentrations, and mixing ratios of sample and calibrants. Internal calibration using the information in the lists results in successful calibration, and all the data presented in this study show root-mean-square errors between the theoretical and obtained m/z numbers of less than 0.4 ppm. The information presented in this study provides an important guideline for researchers working on complex mixtures with ultrahigh-resolution mass spectrometry.