Combination Run of U.S. EPA Methods 521 and 522, Nitrosamines and 1,4-Dioxane, on Rxi®-5Sil-MS by CSR-LVSI

Significance of the Topic

Nitrosamines and 1,4-dioxane are classified as emerging water contaminants due to their carcinogenicity and persistence in the environment. Accurate measurement is essential for compliance with regulatory limits and to protect public health.

Objectives and Study Overview

This study demonstrates a combined gas chromatography–mass spectrometry (GC-MS) method that merges U.S. EPA Methods 521 (nitrosamines) and 522 (1,4-dioxane) on a single Rxi®-5Sil-MS column. The goal is to streamline analysis, reduce instrument downtime, and achieve reliable quantification of all target analytes in one run.

Methodology and Instrumentation

The analytical setup includes:

• Column: Rxi®-5Sil MS, 30 m × 0.25 mm ID, 1.00 µm film, with 10 m guard column
• Detector: Quadrupole GC-MS (Agilent 7890A GC with 5975C MSD) in selected ion monitoring (SIM) mode
• Injection: 50 µL splitless into a 275 °C inlet, custom liner with quartz wool
• Oven Program: 35 °C (1.5 min), ramp to 50 °C at 50 °C/min (7.1 min), then to 320 °C at 11.12 °C/min (1.5 min hold)
• Carrier Gas: Helium, flow‐programmed from 5.08 mL/min to 2.0 mL/min
• SIM Program: Six time windows monitoring characteristic m/z ions for internal standards, nitrosamines, 1,4-dioxane, and tetrahydrofuran
• Temperatures: Transfer line 320 °C, source 230 °C, quadrupole 150 °C

Main Results and Discussion

The combined run achieved baseline separation of 14 analytes, including deuterated internal standards. Retention times spanned 11.0–20.0 min. Detection limits for nitrosamines reached low ng/mL levels, and 1,4-dioxane was quantified at 50 ng/mL with high reproducibility. Chromatograms showed clear peak resolution, minimal matrix interference, and stable SIM response across replicate injections.

Benefits and Practical Applications

• One-run analysis reduces total runtime and solvent consumption
• Improved laboratory throughput for drinking water monitoring
• Enhanced method robustness by eliminating column changes between methods
• Applicable to QA/QC laboratories and environmental testing facilities

Future Trends and Potential Applications

Advances may include coupling this approach with high-resolution MS for confirmation, miniaturizing GC-MS for field deployable units, and extending the multi-analyte strategy to other regulated contaminants such as haloacetic acids or perfluorinated compounds.

Conclusion

The combined EPA Methods 521/522 on an Rxi®-5Sil-MS column offers a streamlined, sensitive, and reliable GC-MS solution for simultaneous measurement of nitrosamines and 1,4-dioxane in water. This integrated protocol enhances analytical efficiency and supports regulatory compliance.

References

1. U.S. EPA Method 521: Determination of Nitrosamines in Drinking Water
2. U.S. EPA Method 522: Determination of 1,4-Dioxane in Drinking Water
3. Restek Corporation. Combination Run of U.S. EPA Methods 521 and 522 on Rxi®-5Sil-MS.