Microwave Plasma Atomic Emission Spectroscopy (MP-AES)

Significance of MP-AES in Elemental Analysis

Microwave Plasma–Atomic Emission Spectroscopy (MP-AES) is a transformative atomic spectroscopy technique that uses a nitrogen-based microwave plasma. By eliminating acetylene and other flammable or costly gases, MP-AES delivers high-performance multi-element analysis with lower operational costs, improved safety, and unattended operation. Its robust toroidal plasma source (≈5000 K) and advanced optics enable wide linear dynamic range, low detection limits (low ppb to high % levels), and superior matrix tolerance. MP-AES meets critical needs across food/agriculture, geochemistry, environmental testing, and pharmaceuticals.

Methodology and Instrumentation

Agilent’s 4100/4200 series MP-AES instruments integrate:

• Microwave Excitation Assembly to sustain a stable nitrogen plasma;
• Easily aligned Easy-Fit torch or Inert Torch (for HF digests) and OneNeb or OneNeb Series 2 inert nebulizer;
• Humidified or mass-flow controlled nebulizer gas for long-term stability on high-TDS samples;
• Plug-and-play Advanced Valve System (AVS 4) for high-throughput, minimizing consumable wear;
• MP Expert software for automated wavelength selection, method optimization, and Fast Linear Interference Correction (FLIC) for structured background and spectral overlaps.

The method typically involves simple acid digestion (flame assay, aqua regia, DTPA, or microwave HF/acids) and single-dilution sample prep.

Primary Results and Discussion

MP-AES has been validated across numerous sample types:

• Food and agriculture: sub-ppb detection of As in wines by HG-MP-AES; major nutrient analysis in milk, juices, and soils; multi-element profiling in wines for provenance.
• Geochemistry and mining: direct fire-assay gold determination (MDL ≈ 7 ppb) with 30 s/sample throughput; major and trace elements in soils and nickel alloys including HF digests with inert sample introduction.
• Environmental: major and trace metal quantification in river sediments, domestic sludge, and soil extracts with MDLs down to sub-ppm and long-term stability RSD < 2% over 8–12 h.

Excellent recoveries (90–110%) and calibration linearity (r^2 > 0.999) demonstrate MP-AES accuracy and precision.

Practical Applications and Benefits

MP-AES suits high-sample throughputs at low cost of ownership. Robust instrument design reduces sample prep (no burner changes or flame-only modes), simplifies operation, and lowers consumable turnover. In geochemical or remote settings, MP-AES with a nitrogen generator enables on-site analysis. Relative to FAAS, MP-AES offers:

• Up to 50–90% reduction in gas costs;
• Expanded dynamic range to ppm–% in one measurement;
• Automated interference correction (FLIC, IEC) for complex matrices;
• Unattended multi-element operation for trace to major levels.

Future Trends and Opportunities

MP-AES is poised to expand in regulated testing, field deployable analysis, and high-matrix applications. Integration with automation and LIMS, on-line sample preparation, and advanced data analytics (chemometrics) will further enhance productivity. The inert torch and HF compatibility open new applications in material science and metallurgy. Continued software development will refine interference correction and simplify method transfer.

Conclusion

Agilent MP-AES offers a unique combination of low operating cost, enhanced safety, and high analytical performance. Its wide dynamic range, low detection limits, matrix tolerance, and ease-of-use make it a preferred choice for diverse elemental analysis tasks in food safety, environmental monitoring, geochemistry, and pharmaceutical testing.

References

• U.S. EPA 40 CFR Part 136 Appendix B, 2011.
• Pohl and Prusisz, Talanta 71, 2007.
• Milestone UltraWAVE Application Notes.