Determination of nitrosamines in water by liquid chromatography tandem mass spectrometry

Importance of the topic

Nitrosamines are potent carcinogenic contaminants emerging in drinking and environmental waters due to industrial discharges and disinfection processes. Their occurrence at trace levels poses significant health risks, prompting international agencies to establish advisory or regulatory limits. Sensitive detection of these compounds is essential for ensuring water safety and compliance with guidelines.

Study objectives and overview

This study presents a robust analytical method for simultaneous quantification of eight common nitrosamines in water matrices. Using solid-phase extraction (SPE) for preconcentration and cleanup, combined with liquid chromatography–tandem mass spectrometry (LC-MS/MS), the work aims to achieve sub‐nanogram-per-liter detection limits and high accuracy for routine environmental monitoring.

Methodology and sample preparation

Water samples were filtered through 0.22 µm membranes. An isotopically labeled internal standard (D14-NDPA) was spiked prior to SPE to correct for variability. SPE was performed following USEPA Method 521 protocols, concentrating analytes from 500 mL of sample. Eluted extracts were evaporated to dryness and reconstituted in 1 mL of 5% methanol/water for analysis.

Used instrumentation

• Agilent 1290 Infinity II UHPLC system
• Agilent 6470 triple quadrupole mass spectrometer
• Poroshell 120 EC-C18 column (100 × 2.1 mm, 2.7 µm)
• Mobile phases: 0.1% formic acid in water (A) and methanol (B)

Chromatographic separation was achieved with a linear gradient from 5% to 95% B in 4 minutes at 0.4 mL/min, 40 °C, and 10 µL injection volume. Mass spectrometric detection used APCI in positive mode, monitoring two MRM transitions per analyte for selectivity.

Main results and discussion

Calibration curves covering 1–200 µg/L exhibited excellent linearity (R² ≥ 0.996). Method limits of detection ranged from 0.11 to 0.34 ng/L, achieving sub‐ng/L sensitivity. Spike recovery experiments in river water at 5 and 20 ng/L levels yielded 67–89% recoveries with RSDs below 5.3%. Analysis of local surface water demonstrated that nitrosamine concentrations were largely below detection limits, confirming low environmental background in surveyed sites.

Benefits and practical applications

The described protocol provides:

• High sensitivity for trace-level nitrosamines
• Reliable quantitation via isotopic dilution
• Efficient sample throughput suitable for routine monitoring

This approach can be implemented in regulatory, industrial, and research laboratories for water quality assessment and risk management.

Future trends and opportunities

Advances in ultrahigh-performance chromatography and high-resolution mass spectrometry may further lower detection limits and expand the range of detectable nitrosamine analogues. Automation of SPE and integration with online systems could improve throughput. Emerging studies could focus on transformation products formed during advanced oxidation and treatment processes.

Conclusion

The LC-MS/MS method combined with SPE enrichment offers a sensitive, selective, and accurate tool for quantifying eight priority nitrosamines in water at sub‐nanogram-per-liter levels. Its performance meets stringent guidelines and supports effective environmental monitoring and public health protection.

References

1. Jeffrey W. A. et al. Environ. Sci. Technol. 2004, 38, 4835–4841.
2. World Health Organization. Guidelines for Drinking-Water Quality, 3rd ed., 2008.
3. Health Canada. Guideline Technical Document — N-Nitrosodimethylamine, 2011.
4. Agilent Application Note 5991-9224EN. Nitrosamines Analysis in Drinking Water Using GC/MS/MS.
5. US EPA. Determination of Nitrosamines in Drinking Water by SPE and GC-MS/MS, EPA/600/R-05/054.