Quantification of nitrosamines in water by automated PAL SPME-Arrow and GC/MS

Significance of the Topic

N-Nitrosamines are potent carcinogens that can form in water through reactions of amines with nitrites. Their trace-level presence in drinking and environmental waters poses serious health risks. Sensitive, reliable analytical methods are essential for monitoring these compounds and ensuring water safety.

Objectives and Overview of the Study

This study aimed to develop and validate a fully automated solid-phase microextraction (SPME) Arrow method coupled with gas chromatography/mass spectrometry (GC/MS) for quantifying seven common N-nitrosamines in aqueous samples. A key goal was to compare traditional Carboxen/PDMS fibers with Carbon WR SPME Arrows in terms of extraction efficiency and analytical performance.

Methodology

Sample preparation involved 10 mL water spiked with salts (4 g KCl) in a 20 mL headspace vial. After preconditioning and incubation at 50 °C with agitation at 500 rpm, analytes were extracted for 30 min by immersing the SPME Arrow. Thermal desorption occurred at 260 °C for 2 min directly into the GC inlet. Chromatographic separation used a 60 m × 0.25 mm, 25 µm BGB Wax 20M column, hydrogen carrier gas at 10 psi, and a temperature program from 50 °C (1 min) ramped to 240 °C at 10 °C/min.

Used Instrumentation

• PAL RTC and RSI autosampler with SPME Arrow tool and conditioning module
• Heatex Stirrer for controlled agitation
• Varian 3400 gas chromatograph
• Varian Saturn ion trap mass spectrometer

Main Results and Discussion

Carbon WR SPME Arrows delivered a 3–5× higher detector signal compared with Carboxen/PDMS fibers. Calibration curves for selected nitrosamines were linear over 0–1200 ng/L (R² > 0.99). Limits of detection (S/N > 3) ranged from 5 ng/L (N-nitrosodipropylamine) to 50 ng/L (N-nitrosopyrrolidine). Repeatability at 1 µg/L showed relative standard deviations of 4–12%. By overlapping extraction and GC runs, analysis of seven samples required approximately 240 min.

Benefits and Practical Applications of the Method

• High sensitivity for trace nitrosamines in water matrices
• Automated workflow enhances reproducibility and throughput
• Applicable to environmental monitoring, drinking water quality control, and regulatory compliance

Future Trends and Applications

Advances may include integration with high-resolution mass spectrometry, expansion to other volatile contaminants, on-site field deployable SPME Arrow systems, and further automation to support high-throughput water analysis in regulatory and industrial laboratories.

Conclusion

The automated PAL SPME-Arrow GC/MS method provides robust, reproducible, and sensitive quantification of multiple nitrosamines in water. The superior extraction efficiency of Carbon WR Arrows and automation capabilities make it an effective tool for routine environmental and quality-assurance analyses.

References

• Grebel JE, Young CC, Suffet IH. J Chrom A. 2006;1117:11–18.