WCPS: Analysis Of Fuel Samples By Microwave Plasma - Atomic Emission Spectrometry

Importance of the Topic

The presence of trace elements in gasoline and diesel fuels can lead to engine corrosion and deposits at elevated temperatures which jeopardizes performance and longevity of engine and turbine components.

Objectives and Study Overview

This study evaluates the capability of microwave plasma atomic emission spectrometry for rapid and reliable determination of magnesium calcium sodium and potassium in highly volatile fuel matrices. The goal is to demonstrate low detection limits high precision and direct analysis without extensive sample preparation.

Methodology and Instrumentation

A microwave plasma atomic emission spectrometer equipped with a magnetically coupled plasma excitation source was employed. Key components include:

• OneNeb inert nebulizer and double pass cyclonic spray chamber with IsoMist cooling to stabilize volatile samples
• External Gas Control Module for controlled air injection to prevent carbon buildup and maintain plasma stability
• Nitrogen plasma generated from compressed air eliminating need for flammable gases and hollow cathode lamps
• MP Expert software facilitating standard addition calibration and automatic background correction

Calibration was performed by standard addition for gasoline due to volatility and by matrix matched standards for diesel following EN 14538. Method detection limits were calculated from blank replicates.

Main Results and Discussion

The method achieved detection limits in the low parts per billion range sufficient for fuel quality requirements. Excellent linearity was observed with correlation coefficients above 0.999 for all elements. Spike recoveries for Mg Ca Na and K fell within 95 to 100 percent in both gasoline and diesel samples confirming accuracy. The cooled spray chamber and EGCM enabled stable plasma even at high organic loading while auto background correction compensated for carbon emissions.

Benefits and Practical Applications

• Direct analysis of volatile gasoline without dilution or preparation saves time and reduces handling risks
• Elimination of flammable gas supplies lowers operating costs and enhances laboratory safety
• Low detection limits and high throughput support routine monitoring per ASTM and EN fuel standards
• Automated software features allow rapid method development and operation by nonexpert users

Future Trends and Opportunities

• Integration with automated sample introduction systems for higher throughput
• Expansion to other challenging matrices such as aviation fuels and biofuel blends
• Coupling with separation techniques for speciation analysis of trace metals
• Advances in miniaturized plasma sources for field portable fuel testing

Conclusion

Microwave plasma atomic emission spectrometry offers a robust low cost and safe solution for routine trace element analysis in gasoline and diesel fuels. The technique delivers excellent sensitivity precision and accuracy while simplifying sample preparation and reducing operational complexity.