Folli Gabriely S, Souza Lindamara M, Araújo Bruno Q, Romão Wanderson, Filgueiras Paulo R
Center of Competence in Petroleum Chemistry - NCQP, Laboratory of Research and Development of Methodologies for Analysis of Oils - LabPetro, Chemistry Department, Federal University of Espírito Santo, Vitória, Brazil.
Petroleomic and Forensic Chemistry Laboratory, Department of Chemistry, Federal University of Espírito Santo, Vitória, Brazil.
Rapid Commun Mass Spectrom. 2020 Sep;34 Suppl 3:e8861. doi: 10.1002/rcm.8861. Epub 2020 Aug 3.
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) is an important analytical technique used for the elucidation of crude oil polar compounds at the molecular level, providing thousands of heteroatom compounds in a single analysis. Due to the high resolution, the complexity of data produced, and steps involved in spectra acquisition and processing, it is necessary to estimate its intermediate precision.
Intermediate precision was estimated for positive- and negative-ion ionization modes (ESI(±)) using Composer® software for two Brazilian crude oil samples. The analytical parameters evaluated were the class distribution histogram, the double bond equivalent (DBE) distribution, and the DBE versus carbon number. The statistical parameters used to study the intermediate precision were calculated from the average, standard deviation, confidence interval (significance level at 5%), coefficient of variation (CV), intermediate precision limit (ISO 5725), and principal component analysis (PCA).
Two crude oil samples (A and B) were analyzed, in triplicate, for seven consecutive days by ESI(±) FT-ICR MS. The assigned class limit by ESI(+) for crude oil A was 0.42% (O S[H] class) and for crude oil B was 0.04% (N O S[H] class). The assigned DBE intensity limits for the two crude oils were 0.04% for ESI(+) and 0.013% for ESI(-). The PCA for ESI(-) and ESI(+) modes presented better precision for crude oils B and A, respectively.
The most abundant classes and DBE of the majority class (i.e., with the highest intensity) are the parameters produced from the Composer® software that had the highest precision and can be used to estimate crude oil properties. The DBE values presented lower intermediate precision limit values (0.04%) than the assigned class values (0.4%). According to CV and PCA, ESI(+) was more precise for crude oil A (83% precision) and ESI(-) for crude oil B (84% precision).
电喷雾电离傅里叶变换离子回旋共振质谱法（ESI FT-ICR MS）是一种重要的分析技术，用于在分子水平上阐明原油中的极性化合物，一次分析可提供数千种含杂原子化合物。由于其高分辨率、所产生数据的复杂性以及光谱采集和处理所涉及的步骤，有必要评估其中间精密度。
使用Composer®软件对两个巴西原油样品的正离子和负离子电离模式（ESI(±)）的中间精密度进行评估。评估的分析参数包括类别分布直方图、双键当量（DBE）分布以及DBE与碳原子数的关系。用于研究中间精密度的统计参数是根据平均值、标准差、置信区间（显著性水平为5%）、变异系数（CV）、中间精密度限值（ISO 5725）以及主成分分析（PCA）计算得出的。
通过ESI(±) FT-ICR MS对两个原油样品（A和B）连续七天进行了三次重复分析。ESI(+)对原油A的指定类别限值为0.42%（O S[H]类），对原油B的指定类别限值为0.04%（N O S[H]类）。两种原油ESI(+)的指定DBE强度限值为0.04%，ESI(-)为0.013%。ESI(-)和ESI(+)模式的PCA分别对原油B和A呈现出更好的精密度。
Composer®软件生成的大多数类别（即强度最高的类别）中最丰富的类别和DBE是具有最高精密度的参数，可用于估计原油性质。DBE值的中间精密度限值（0.04%）低于指定类别值（0.4%）。根据CV和PCA，ESI(+)对原油A的精密度更高（83%精密度），ESI(-)对原油B的精密度更高（84%精密度）。
