Determination of Carbon and Nitrogen in Carbon Black and Graphite

Importance of the Topic

Carbon black and graphite are fundamental carbon-based materials with critical roles in industrial and environmental applications. Accurate measurement of their carbon and nitrogen content is essential for process control, emissions reporting, and quality assurance.

Objectives and Overview of the Study

This application note presents a validated analytical procedure using the LECO CN928 macro combustion analyzer for simultaneous determination of carbon and nitrogen in carbon black and graphite, following a modified ASTM D7633 method.

Instrumentation Used

• LECO CN928 macro combustion carbon and nitrogen determinator
• High-temperature horizontal ceramic combustion furnace (1350 °C)
• Thermoelectric cooler and gas ballast for moisture removal
• NDIR detector for CO₂ and thermal conductivity cell for N₂
• 3 cm³ and 10 cm³ aliquot loops with He or Ar carrier gas

Methodology

Samples of carbon black and graphite were dried (125 °C and 105 °C respectively) and stored in a desiccator. Approximately 0.20 g of each sample was weighed into ceramic combustion boats. Under pure oxygen combustion, combustion gases were cooled, dried, and transferred via aliquot loops into detectors. Calibration was performed using certified reference materials (phenylalanine and EDTA) with linear regression for carbon and forced-through-origin regression for nitrogen. Helium provided higher sensitivity at low nitrogen levels compared to argon.

Key Results and Discussion

Carbon recoveries for graphite were on average 100.0% with RSD <0.1% across both loop sizes and carrier gases. Carbon black samples showed recoveries around 93.7% with nitrogen levels averaging 0.24% (He) and 0.26% (Ar) with precision better than 0.01%. Nitrogen in graphite was below the detection limit. The 10 cm³ loop optimized low-level nitrogen precision, while the 3 cm³ loop increased reagent life.

Benefits and Practical Applications

• Reliable quantification of carbon and nitrogen for emissions reporting and yield estimation
• Quality control in manufacturing of carbon black and graphite materials
• Optimization of process parameters based on nitrogen content
• Flexible carrier gas selection for sensitivity and cost-effectiveness

Future Trends and Applications

Advances may include smaller aliquot volumes, integration with automated sample handling, alternative carrier gases for sustainability, and application to a wider range of carbonaceous materials. Data integration with laboratory information management systems (LIMS) and artificial intelligence–driven data analysis are expected to enhance throughput and insight.

Conclusion

The LECO CN928 method offers a robust, precise approach for simultaneous determination of carbon and nitrogen in carbon black and graphite, meeting modified ASTM D7633 criteria and supporting industrial quality control and environmental compliance.

References

• ASTM D7633: Standard Test Method for Carbon Black—Carbon Content
• LECO Application Note: Determination of Carbon and Nitrogen in Carbon Black and Graphite, Form No. 203-821-684, 2024