ASTM D8322: Elemental Analysis of Crude Oil and Residual Fuels using MP-AES

Importance of the topic

Trace elements such as iron, vanadium, nickel, and others can impair refinery catalysts, reduce product yield, and increase atmospheric emissions when present in crude oil and residual fuels. Monitoring these impurities is essential for efficient desalting, distillation, and downstream processing. Traditional approaches often require multiple analytical techniques and laborious sample preparation, limiting throughput and raising costs.

Objectives and overview

This work assesses the performance of the ASTM D8322-20 method using microwave plasma atomic emission spectroscopy (MP-AES) to measure V, Ni, Ca, Na, Al, Si, Zn, and S in residual fuels, and Fe, V, Ni, Ca, Na, K, and S in crude oils. The goal is to validate a unified “dilute and shoot” protocol that replaces several conventional test methods and reduces the complexity of sample handling.

Methodology and instrumentation

The method employs an Agilent 4210 MP-AES equipped with MP Expert software and an organics analysis kit comprising an External Gas Control Module, OneNeb Series 2 nebulizer, and double-pass cyclonic spray chamber. Nitrogen plasma is generated onsite via a nitrogen generator or in-house supply, eliminating flammable gases. Samples and standards are prepared in o-xylene with mineral oil to a 10 % w/w oil concentration. Calibration curves for each element exhibit excellent linearity across relevant concentrations. Quality control includes continuing calibration verification every ten samples and spike recovery tests.

Main results and discussion

Calibration curves for Fe, Ni, Si, and V demonstrated linear response with correlation coefficients near unity. Over four days, continuing calibration standards yielded recoveries within ±20 %, confirming stability and precision. Certified reference materials for crude oil and residual fuel produced recoveries within ±10 % of certified values (±20 % for calcium in fuel oil), reflecting high accuracy. Spike recoveries in actual samples were within ±20 %, demonstrating method robustness across a range of matrices. Quantitative analysis of diverse real samples showed variable concentrations of trace elements, highlighting the wide applicability of the method.

Benefits and practical applications

• Single-technique analysis replaces multiple ASTM methods, reducing method complexity.
• “Dilute and shoot” sample preparation lowers cost, time, and sources of error.
• Nitrogen-based plasma improves safety by eliminating flammable gases and enables field deployment.
• On-board diagnostics and software guidance enhance reproducibility among operators.

Future trends and possibilities

Advances may include portable MP-AES systems for on-site monitoring, expansion of analyte panels to cover additional contaminants, and integration with automated sample handling and data processing workflows. Machine learning tools could further optimize calibration and drift correction, improving long-term stability and throughput.

Conclusion

The ASTM D8322-20 MP-AES method delivers accurate, precise, and reproducible multi-element analysis of crude oils and residual fuels with streamlined sample preparation and reduced operational costs. Its robustness and safety profile make it a compelling choice for routine quality control and regulatory compliance in the petroleum industry.

References

1. Significance of Tests for Petroleum Products 9th ed., Chapter 23, Analytical Methods for Determination of Inorganic Species in Petroleum Products and Lubricants, ASTM International, 2018.
2. ASTM D8322-20, Standard Test Method for Determination of Elements in Residual Fuels and Crude Oils by MP-AES, ASTM International, 2020.
3. Measuring Elements in Residual Fuels and Crude Oil per Method ASTM D8322 Using an Agilent 4210 MP-AES, Agilent Technologies, publication 5994-2460EN.
4. ASTM D5708-15(2020)e1, Test Methods for Determination of Ni, V, and Fe in Crude Oils by ICP-OES, ASTM International, 2020.
5. ASTM D5863-00a(2016), Test Methods for Determination of Ni, V, Fe, and Na in Crude Oils by Flame AAS, ASTM International, 2016.
6. Agilent MP Expert Software Guide, Agilent Technologies, publication 5990-8975EN.