Analysis of Lubricant Additive Elements per ASTM D 4927 by X-Ray Fluorescence

Analysis of Lubricant Additive Elements by WDXRF According to ASTM D 4927

Significance of the Topic

Additive elements in lubricating oils are critical for engine performance, wear protection and compliance with industrial standards. Accurate quantification of elements such as Ba, Ca, Cu, Mg, P, S and Zn ensures optimal additive dosing and quality control in the petroleum and automotive industries.

Objectives and Study Overview

The study aims to demonstrate the application of wavelength dispersive X-ray fluorescence (WDXRF) for quantitative analysis of key lubricant additives following the ASTM D 4927 protocol. It evaluates calibration strategies, background and matrix corrections to achieve reliable results over a wide concentration range.

Methodology

• Sample preparation: 20 g of oil in Chemplex 1440 liquid cell sealed with 4 μm polypropylene film; triplicate measurements to average sample heterogeneity.
• Calibration: Use of CONOSTAN and Alpha Research standard series per ASTM D 4927; theoretical alpha corrections via fundamental parameter algorithms to account for matrix effects.
• Measurement conditions: Rh anode X-ray tube at 30 kV/90 mA; counting times of 30 s per element (60 s for Mg); single background measurement per element for net intensity calculation.

Instrumentation Used

• Thermo Scientific ARL PERFORM’X 4200 W wavelength dispersive XRF spectrometer.
• 5GN+ Rh X-ray tube with 50 μm Be window and low-current filament for enhanced stability.
• Configuration: 6 primary beam filters, 4 collimators, up to nine crystals, two detectors, helium purge system and liquid sample LoadSafe cassette with Secutainer safety features.

Results and Discussion

• Calibration ranges achieved from limits of detection to defined concentration upper limits (e.g., Ba up to 1 %, Ca up to 0.5 %, P up to 0.5 %).
• Standard Error of Estimate (SEE) values indicate high accuracy: 2 ppm for Mg, 0.02 % for S, 28 ppm for P, 20 ppm for Ca, 2.7 ppm for Cu, 6.6 ppm for Zn and 50 ppm for Ba.
• Linear calibration curves for P, Ca and Ba demonstrate excellent agreement between predicted and actual concentrations across the tested ranges.

Benefits and Practical Applications

• Rapid, non-destructive analysis with minimal sample preparation.
• Wide dynamic range from ppm to percent levels for multiple additive elements.
• Suitability for routine QA/QC, additive formulation control and failure analysis in industrial laboratories.

Future Trends and Potential Applications

• Integration of advanced detector technologies to reduce counting times to 10–20 s per element.
• Enhanced fundamental parameter models for more complex oil matrices.
• In-line and at-line monitoring of lubricant quality in production environments.
• Automation and digital workflows connecting XRF systems to laboratory information management systems (LIMS).

Conclusion

WDXRF analysis using the Thermo Scientific ARL PERFORM’X system provides accurate, efficient quantification of lubricant additive elements compliant with ASTM D 4927. The method’s robustness, speed and low operational complexity make it a valuable tool for industrial and research laboratories focused on lubricant quality and performance optimization.

Reference

Thermo Fisher Scientific Inc. Application Note AN41668: Analysis of Lubricant Additive Elements per ASTM D 4927 by X-Ray Fluorescence (2019).