High-Throughput Multi-Elemental Analysis of Crude Oil

Significance of the Topic

Accurate determination of trace metals such as nickel (Ni) and vanadium (V) in crude oil is critical for meeting trading specifications, protecting refinery catalysts, and ensuring product quality. As global benchmarks like West Texas Intermediate (WTI) impose strict limits (Ni <8 ppm, V <15 ppm), reliable, high-throughput multi-element analysis is essential for petroleum laboratories, quality control, and regulatory compliance.

Objectives and Study Overview

This study evaluates a fast, robust method for quantifying 23 elements in crude oil and residual fuels using the Agilent 5110 Vertical Dual View (VDV) ICP-OES with an AVS 7 switching valve. Following ASTM D5708-15, the method aims to deliver accurate Ni and V measurements in a high-throughput format suitable for routine analysis and long-term operations.

Used Instrumentation

• Agilent 5110 VDV ICP-OES with solid-state RF plasma and vertical torch
• AVS 7 high-speed switching valve
• SPS 4 autosampler
• Seaspray concentric glass nebulizer, 1.4 mm i.d. organics torch
• Vista Chip II CCD detector
• ICP Expert software including Applet mode, Fitted Background Correction (FBC), IntelliQuant

Methodology and Sample Preparation

Crude oil samples covering a range of API gravities were diluted 1:10 to 1:20 in o-xylene with a matrix modifier and yttrium internal standard. Calibration standards for 23 elements were prepared at 0.1–50 mg/kg (S at 200–2000 mg/kg). The method parameters included radial viewing mode, three replicates, 8 s read time, and fitted background correction. Quality control used NIST SRMs 1634c, 8505, and an ASI Standards multi-element solution.

Results and Discussion

Method detection limits ranged from <0.006 mg/kg (Mg) up to ~2.9 mg/kg (Sn). Recoveries for Ni, V, and S in SRMs were within ±10% of certified values. A QC solution yielded element recoveries within 10% and RSDs below 3%. Long-term stability over ~400 samples (6 h) showed QC recoveries within ±10% and RSD <3%. Twenty crude oil samples were screened in 52 s each, consuming 17 L of argon per sample. Nine samples met WTI Ni and V specifications. IntelliQuant heat maps provided semiquantitative screening of up to 70 elements in under 15 s, aiding interference identification and method development.

Benefits and Practical Applications

• High throughput: complete multi-element analysis in under 1 minute per sample
• Reduced argon consumption via AVS 7 switching valve (≈50% savings)
• Wide dynamic range and multiple wavelengths per element via Vista Chip II detector
• Simplified operation for routine users through ICP Expert Applet
• Automatic background correction and rapid semiquantitative screening with IntelliQuant

Future Trends and Opportunities

Advances may include remote or on-line sampling integration, enhanced automation with AI-driven method optimization, real-time process monitoring, and expansion to emerging biofuel and bitumen matrices. Further improvements in detector technology and software algorithms will continue to increase sensitivity, robustness, and throughput for complex petroleum analyses.

Conclusion

The Agilent 5110 VDV ICP-OES with AVS 7 switching valve provides a comprehensive, accurate, and efficient solution for multi-element analysis of crude oil. Meeting ASTM D5708-15 requirements, the method offers high throughput, low operating costs, and robust long-term stability for routine quality control of Ni, V, and a broad suite of other elements.

Reference

1. CME Group NYMEX Light Sweet Crude Oil Futures, 2017.
2. ASTM D5708-15 Standard Test Methods for ICP-AES of Crude Oils, ASTM Int., 2015.
3. Agilent Benefits of a Vertically Oriented Torch, Pub. 5991-4854EN.
4. Agilent CCD and CID Detectors, Pub. 5991-4842EN.
5. Agilent Fitted Background Correction, Pub. 5991-4836EN.
6. Agilent AVS 6/7 Switching Valve, Pub. 5991-6863EN.
7. Agilent IntelliQuant Overview, Pub. 5991-6876EN.
8. Agilent ICP Expert Software, Pub. 5991-7720EN.
9. Agilent A21 Wear Metal Standard Certificate, Part 5190-8713.