Nitrosamine Analysis by Gas Chromatography and Agilent 255 Nitrogen Chemiluminescence Detector (NCD)

Significance of the Topic

N-nitrosamines represent a class of compounds with well-documented carcinogenic and mutagenic properties. They can arise in food products, tobacco, rubber and cosmetic materials, as well as environmental samples. Accurate quantification of these trace-level analytes is critical for regulatory compliance and public health protection.

Objectives and Study Overview

This technical overview demonstrates a rapid and selective method for nitrosamine determination using capillary gas chromatography coupled with an Agilent 255 Nitrogen Chemiluminescence Detector (NCD). The article presents chromatographic separation of key nitrosamines, evaluates detector performance in terms of sensitivity, specificity and reproducibility, and compares two column chemistries (HP-5 and DB-WAX).

Methodology and Instrumentation

The analysis employs an Agilent 255 NCD operated in specialized nitrosamine mode, which selectively detects the thermally unstable nitroso functionality and yields an equimolar response across compounds. Detection is free from hydrocarbon interference and quenching effects common in other nitrogen-specific detectors. Key conditions include:

• Column chemistries: nonpolar HP-5 (30 m×0.32 mm, 0.25 µm film) and polar DB-WAX (30 m×0.53 mm, 1 µm film)
• Temperature programs: HP-5 oven ramp from 60 °C to 180 °C; DB-WAX ramp from 50 °C to 200 °C
• Injection: split mode (10:1) for HP-5, on-column for DB-WAX
• Carrier flow: constant helium at 1.7 mL/min (HP-5) and 3.5 mL/min (DB-WAX)
• Detector: dual‐plasma NCD with optimized burner conditions for nitrosamine selectivity

Main Results and Discussion

Using the HP-5 column, nine nitrosamines at 2 µg/mL were baseline resolved within 13 minutes, with retention times ranging from 1.45 to 12.84 minutes. A 4.5-day precision study (33 injections of a 100 ppb mix) showed relative standard deviations below 6% for most analytes; higher variability (~15%) for N-nitrosodiphenylamine was attributed to known injection‐port decomposition. With the DB-WAX column, on-column injection of a 100 ng/mL standard achieved excellent sensitivity and peak shape, highlighting the polar phase’s suitability for trace‐level nitrosamine screening.

Benefits and Practical Applications of the Method

• High specificity for nitrosamines with minimal matrix interference
• Equimolar detector response simplifying calibration and quantitation
• Wide linear dynamic range spanning at least four orders of magnitude
• Robust day‐to‐day reproducibility suitable for routine QA/QC workflows
• Flexibility to use nonpolar or polar columns for targeted separations

Future Trends and Potential Applications

Advances may include coupling the NCD with mass spectrometry for structural confirmation, miniaturized GC systems for field analysis, automated sample preparation for high throughput, and method standardization for regulatory protocols. Integration with data‐analysis software and multi‐detector platforms could further enhance nitrosamine screening across diverse matrices.

Conclusion

The combination of capillary GC and the Agilent 255 NCD provides a reliable, sensitive and specific solution for trace‐level nitrosamine analysis. Its equimolar response, robustness and adaptability to different columns make it an attractive choice for laboratories engaged in food safety, environmental monitoring and consumer‐product testing.

References

• Agilent Technologies. Nitrosamine Analysis by Gas Chromatography and Agilent 255 Nitrogen Chemiluminescence Detector. Technical Overview, Publication 5989-6773EN, 2007.