Trace Level Direct Determination of Phosphorus in Petroleum Products with High Particulate Content

Abstract

Petrochemical samples are difficult matrices, as they cover a wide range of volatilities, densities, viscosities, and quantities of particulate matter. The analysis of organic samples has always been a challenge for inductively coupled plasma – optical emission spectrometry (ICP-OES). More volatile than aqueous solutions, an organic matrix affects the plasma robustness and stability and creates complicated spectral backgrounds. As a result, the detection limits in organic as compared to aqueous samples are degraded. The goal of this study was to develop a robust and reliable method for trace level phosphorus determination in petroleum products with high particulate content. Selecting the correct sample introduction system, particularly the nebulizer as its most critical component, and optimization of instrument operating parameters are expected to significantly improve the analytical performance of the developed method. Three nebulizers were evaluated, and the analytical performance for the determination of low phosphorus concentration in a number of challenging petrochemical samples with high particulate content was compared. The evaluation included one concentric and two non-concentric nebulizers specifically designed to handle samples with large particles. In order to achieve the lowest possible quantification limits, the optimization of the dilution ratio was carried out for each studied matrix. The results clearly showed that the lowest quantification limit of 0.08 mg kg⁻¹ at 1:3 dilution ratio as well as accuracy, precision, and ability to handle samples with high particulate content was achieved by using one of the non-concentric nebulizers.

Keywords:

• Concentric and non-concentric nebulizers
• inductively coupled plasma – optical emission spectrometry (ICP-OES)
• petroleum
• phosphorus

Funding

This study was funded by the Valencian government through the Valencian Institute of Business Competitiveness (IVACE) to promote the excellence in R&D of the technological centers in the Valencian community, through project IMAMCA/2020/1..

Acknowledgments

The authors would like to thank Dr. Sergei Leikin from Texas Scientific Products (TSP) for supplying the nebulizers studied and for all his helpful shared knowledge during the development of the study. In addition, they also would like to thank Ricardo Sales from BP Oil Castellón for providing the studied materials.

Disclosure statement

The authors declare that there are no conflicts of interest.

Additional information

Funding

This study was funded by the Valencian government through the Valencian Institute of Business Competitiveness (IVACE) to promote the excellence in R&D of the technological centers in the Valencian community, through project IMAMCA/2020/1.