Analysis of Nitrosamines in Drinking Water Using the Agilent 5977A Series GC/MSD System

Importance of Topic

Chloramination in water treatment can generate nitrosamines such as NDMA, classified as probable human carcinogens. Monitoring these trace contaminants in drinking water at sub-part-per-trillion levels is essential for public health protection and compliance with regulatory guidelines worldwide.

Objectives and Overview of Study

This study evaluates the Agilent 5977A Series GC/MSD System for detecting six nitrosamines in drinking water. The aim is to achieve limits of detection below those cited in EPA Method 521 without large-volume injection or MS/MS instrumentation.

Methodology and Instrumentation Used

Sample Preparation:

• 500 mL water samples extracted by solid-phase extraction following EPA 521 procedures.
• NDMA-d6 surrogate added pre-extraction; NDPA-d14 internal standard added post-concentration.
• Elution in methylene chloride; concentrated to 1 mL (500× enrichment).

Instrumental Conditions:

• GC: Agilent 7890B with multimode inlet (MMI).
• MS: Agilent 5977A MSD in positive chemical ionization (PCI) mode using methane.
• Column: VF-624ms (20 m × 0.15 mm, 0.84 µm).
• Injection: 2 µL splitless; inlet at 250 °C.
• Oven: 35 °C (4 min) →195 °C at 10 °C/min →240 °C at 15 °C/min (2 min hold).
• Acquisition: Full scan m/z 40–200 and SIM for target/qualifier ions.

Main Results and Discussion

Calibration and Linearity:

• 0.5–50 ppb in methylene chloride; correlation coefficients ≥0.9985.

Detection Limits:

• LODs (3.3σ) ranged 0.018–0.166 ppb in extract (equivalent to 0.036–0.332 ppt in water).
• LOQs (10× LOD) ranged 0.182–1.662 ppb.

Comparison with EPA 521:

• Agilent GC/MSD LODs were 1.9–11× lower than EPA 521 despite a 10× smaller injection and use of single-quadrupole MS.

Benefits and Practical Applications

The method enables:

• High-sensitivity quantitation of nitrosamines without MS/MS.
• Smaller injection volumes for simpler operation.
• Reproducible results via automated sample preparation.

This supports routine monitoring and risk assessment in water quality laboratories.

Future Trends and Possibilities

Potential developments include:

• On-line SPE integration for higher throughput.
• PCI/MS adaptation to other disinfection by-products.
• High-resolution mass spectrometry for enhanced selectivity.

Conclusion

The Agilent 5977A GC/MSD system in PCI mode offers reliable sub-ppt detection of nitrosamines, outperforming EPA Method 521 LODs with minimal injection volume and single-quadrupole instrumentation.

Used Instrumentation

• Agilent 7890B GC with MMI.
• Agilent 5977A MSD in PCI mode.
• Agilent 7696A Sample Prep WorkBench.

References

• EPA Method 521: Determination of Nitrosamines in Drinking Water by SPE-GC/MS/MS.
• Health Canada. Guidelines for Canadian Drinking Water Quality: NDMA.
• World Health Organization. Guidelines for Drinking-water Quality (2008).