Quantitative Evaluation of Non-basic Nitrogen-Containing Compounds in Petroleum-Derived Samples by Direct Injection ESI (-) Orbitrap MS

The quantification of non-basic nitrogen-containing compounds (NCCs) in petroleum-derived samples has become a critical issue due to the undesirable effects of these compounds on the petroleum industry. In addition, there is a lack of analytical methods that allow the direct quantification of NCCs in these matrices. This paper provides strategies for obtaining quantitative information of NCCs in petroleum-derived samples using direct flow injection electrospray ionization (ESI) (-) Orbitrap mass spectrometry without fractionation steps. Benzocarbazole (BC) quantification was performed using the standard addition method. The method was validated, and all analytical parameters demonstrated satisfactory results in the matrix-mix. Paired Student's t-test exhibited the matrix effect (95% confidence level, p < 0.05). Limits of detection ranged from 2.94 to 14.91 mu g L-1, and the limits of quantification ranged from 9.81 to 49.69 mu g L-1. Intraday and interday accuracy and precision were not above 15%. Quantification of non-basic NCCs was carried out based on two approaches. In approach 1, the non-basic NCCs' total content in petroleum-derived samples was determined by the BC concentration and the total abundance correction. The method presented good performance with the average error of 21, 8.3, and 28% for crude oil, gas oil, and diesel samples, respectively. Approach 2 was based on the multiple linear regression model with regression significant at a 0.05 significance level within average relative errors of 16, 7.8, and 17% for the crude oil, gas oil, and diesel samples, respectively. Then, both approaches successfully predicted the quantification of non-basic NCCs by ESI direct flow injection.

Automated summary

This study provides a direct flow injection electrospray ionization (ESI) (-) Orbitrap mass spectrometry method for the quantitative analysis of non-basic nitrogen-containing compounds (NCCs) in petroleum-derived samples, without the need for fractionation steps. The method was validated by quantifying benzocarbazole (BC) using the standard addition method, and demonstrated satisfactory results in the matrix-mix.