Pyrolytic Graphite Platforms – Guidelines for use with the GTA-95 Graphite Tube Atomizer

Significance of the Topic

The pyrolytic graphite platform is crucial in reducing vapor phase chemical interferences and background absorption in graphite furnace atomic absorption spectroscopy. By enabling vaporization in a preheated gaseous environment, it enhances analytical accuracy and precision in complex matrices.

Objectives and Overview

This application note aims to provide detailed guidelines for the effective use of pyrolytic graphite platforms with the Agilent GTA-95 graphite tube atomizer and PSD-95 sample dispenser. It outlines procedures for platform positioning, dispenser adjustment, sample deposition, and temperature program development, along with practical suggestions for challenging matrices.

Methodology and Instrumentation

The technique is based on the L’vov steady‐state approach, where the sample is deposited on a platform preheated to a stable temperature, minimizing cooler vapor‐phase interferences.

Instrumentation:

• Agilent GTA-95 graphite tube atomizer
• PSD-95 programmable sample dispenser
• HP-86 graphics program for peak display

Key procedural steps include:

• Aligning the platform perpendicular to the sample dispenser capillary
• Adjusting capillary depth to position droplets in the platform indentation
• Selecting appropriate sample volumes (10–25 µL) and acid modifiers
• Developing temperature programs for drying, ashing, atomization, and cooldown

Results and Discussion

Comparative profiles demonstrate a significant reduction in background absorption and a temporal shift of the analyte peak when using the platform. The method effectively reduces interferences for volatile elements, while peak shapes for refractory elements may require matrix optimization. Modifying the read step duration improves peak area accuracy without altering the overall temperature cycle.

Benefits and Practical Applications

The platform technique:

• Reduces matrix‐dependent interferences, enhancing data reliability
• Minimizes the need for standard additions through direct calibration
• Improves precision and accuracy in environmental and industrial sample analysis

Future Trends and Applications

Anticipated developments include:

• Integration with automated furnace control systems and advanced software
• Coupling with novel matrix modification strategies and emerging contaminants analysis
• Adaptation for microvolume sampling and alternative platform materials

Conclusion

The guidelines presented enable analysts to optimize platform positioning, dispensing, and temperature programming, delivering accurate and precise results in challenging matrices. The pyrolytic graphite platform remains a valuable tool for reducing interferences in furnace AA.

References

1. P. S. Doidge, Pyrolytic Graphite Platforms, Varian Instruments at Work No. AA-25, Varian Techtron (1982).
2. L. M. Voth, Dealing with Matrix Interferences in the Determination of the Priority Pollutant Metals by Furnace AA, Varian Instruments at Work No. AA-35, Varian Techtron (1983).
3. B. V. Lvov, Electrothermal Atomization – the Way Toward Absolute Methods of Atomic Absorption Analysis, Spectrochimica Acta Part B, 33B 153 (1978).
4. P. S. Doidge, T. N. McKenzie, Applications of the Graphite Platform to the Reduction of Interferences in Graphite Furnace Atomic Absorption Spectroscopy, Varian Techtron (1983).
5. Operation Manual for the GTA-95 Graphite Tube Atomizer, Varian Techtron Publication No. 85-100442-00 (1981).
6. K. G. Brodie, Practical Operation with the GTA-95 Graphite Tube Atomizer, Varian Instruments at Work No. AA-28, Varian Techtron (1983).