Agilent Model 255 Nitrogen Chemiluminescence Detector (NCD) Simultaneous Hydrocarbon Analysis with the NCD and an FID

Significance of the Topic

Chemical analysis of nitrogen-containing compounds within complex matrices is essential for environmental monitoring, pharmaceutical quality control, petrochemical processing, and other industrial applications. The combination of nitrogen-specific chemiluminescence detection (NCD) with a universal flame ionization detector (FID) enables both selective quantification of nitrogen species and broad hydrocarbon profiling in a single analytical run.

Objectives and Overview of the Study/Article

This technical overview demonstrates a method for simultaneous nitrogen-specific and universal hydrocarbon analysis using the Agilent Model 255 Nitrogen Chemiluminescence Detector (NCD) in tandem with an FID. The study evaluates sensitivity, precision, equimolar response, and operational stability under routine laboratory conditions.

Methodology and Instrumentation

Capillary gas chromatography is configured so that the column effluent first enters the FID and then continues into the stainless steel burner of the NCD. Oxygen is used in the FID to prevent background nitric oxide formation, while helium serves as the makeup gas. Key operational parameters include:

1. GC temperature program: 65 °C for 3 minutes, ramp at 25 °C/min to 250 °C, hold for 1 minute
2. Carrier gas: helium at 2.2 mL/min
3. Split injection: 50:1 with 2 µL injection volume
4. NCD burner conditions: 800 °C, hydrogen flow 25 mL/min, oxygen flow 10 mL/min

Instrumentation Used

• Agilent 6890 Gas Chromatograph with electronic pneumatic control (EPC)
• Agilent Model 255 Nitrogen Chemiluminescence Detector
• Flame Ionization Detector modified with oxygen and helium makeup
• Stainless steel burner convertible to Direct Analysis mode for enhanced nitrogen sensitivity
• Capillary column: 30 m HP-5, 0.32 mm ID, 0.25 μm film

Key Results and Discussion

• Simultaneous analysis of nitrobenzene, 3-methylindole, and 9-methylcarbazole at ~25 ppm nitrogen each demonstrates equimolar NCD response and specificity, with no interference from non-nitrogen hydrocarbons.
• Precision over 143 injections across three days shows NCD relative standard deviation (RSD) ≤2.5% and FID RSD ≤1.5%, indicating excellent stability and reproducibility.
• Tandem operation does not compromise FID performance, and the NCD remains unaffected by the hydrocarbon matrix.

Benefits and Practical Applications

• Accurate quantification of trace nitrogen-containing impurities in petrochemical and environmental samples.
• Comprehensive hydrocarbon profiling combined with selective nitrogen detection reduces analysis time and sample handling.
• Enhanced laboratory efficiency and data confidence for QA/QC and research applications.

Future Trends and Potential Applications

• Integration with advanced data analysis algorithms and real-time monitoring systems for process control.
• Expansion of chemiluminescence detection to other heteroatoms (e.g., sulfur, phosphorus).
• Development of portable GC-NCD platforms for field-based environmental and industrial testing.
• Application in emerging fields such as biofuels, food safety, and complex biologics characterization.

Conclusion

The tandem GC-FID/NCD configuration provides a robust, high-throughput approach for simultaneous universal hydrocarbon and nitrogen-specific analysis. Its high specificity, equimolar response, and operational stability make it an invaluable tool for routine laboratory workflows and advanced analytical research.