Nitrosamine Analysis in Drinking Water using GC/MS/MS for Performance Equivalent to EPA Method 521

Significance of the Topic

Nitrosamines such as N-nitrosodimethylamine (NDMA) are emerging contaminants in drinking water known for their carcinogenic potential. Accurate trace-level analysis of these compounds is essential to safeguard public health and support regulatory decisions by agencies such as the U.S. EPA.

Objectives and Study Overview

The primary aim of this project was to evaluate a triple quadrupole gas chromatography tandem mass spectrometry (GC/MS/MS) method against the established ion trap GC/MS protocol defined in EPA Method 521. The goal was to achieve equivalent or superior performance in terms of sensitivity, selectivity, and run time without altering sample preparation procedures.

Instrumental Setup

• Triple quadrupole GC/MS/MS: Agilent 7010 and 7000 systems with high-efficiency sources and extractors.
• Ion trap GC/MS: Varian 4000 with chemical ionization source for comparison.
• GC conditions: VF-5ms capillary column, splitless injection (1 µL), temperature ramp from 35 °C to 280–300 °C.
• Detection: Selective reaction monitoring of characteristic transitions for NDMA, NMOR, NPYR, NDBA, and others at sub-ppt levels.

Methodology

Drinking water samples were processed according to the solid-phase extraction steps described in EPA Method 521 without modification. Following elution and concentration, extracts were analyzed by both GC/IT and GC/MS/MS. Calibration was performed at multiple levels from 0.1 to 10 ppt, and method performance was evaluated in three laboratories. Key performance metrics included limit of detection, lowest concentration minimum reporting level (LCMRL), surrogate recoveries, and holding time stability.

Main Results and Discussion

• GC/MS/MS demonstrated LCMRL and detection limits up to tenfold lower than those achieved by GC/IT, reliably quantifying nitrosamines at sub-ppt levels.
• Run time was reduced from 40 min (GC/IT) to 15 min (GC/MS/MS) by optimizing chromatographic separation, particularly for compounds like NDPA, NPYR, and NMOR.
• Interlaboratory validation showed strong correlation between operators and instruments with surrogate recoveries consistently within 70–130%.
• Holding time tests confirmed extract stability for at least 14 days, aligning with current EPA guidelines.

Benefits and Practical Applications

The optimized GC/MS/MS approach streamlines analysis workflows, improves laboratory throughput, and enhances detection capabilities for routine drinking water monitoring. Its robust performance makes it suitable for regulatory compliance testing and quality assurance/quality control in environmental laboratories.

Future Trends and Opportunities for Use

Ongoing efforts include formal EPA endorsement of the method, expansion of analyte scope to additional nitrosamines, and potential automation of sample preparation. The approach also shows promise for applications in wastewater surveillance and broader environmental testing where ultra-trace detection is required.

Conclusion

The comparison study establishes that triple quadrupole GC/MS/MS offers a performance-equivalent or superior alternative to the traditional ion trap method defined in EPA Method 521. Enhanced sensitivity, reduced analysis time, and reliable interlaboratory reproducibility support its adoption for nitrosamine determination in drinking water.

References

• EPA Method 521 Version 1.0, September 2004, EPA/600/R-05/054
• U.S. EPA Letter of Equivalency for EEA-Agilent 521.1 for Analysis of Nitrosamines in Drinking Water by GC/MS/MS, March 13 2018
• Agilent Application Note 5991-9224EN, collaboration with Eurofins Eaton Analytical and Vogon Laboratories