Lowering Detection Limits for 1,4-Dioxane in Drinking Water Using Large Volume Injection in an Unmodified Splitless GC Inlet

Significance of the Topic

1,4-Dioxane is a water-soluble solvent identified as a probable human carcinogen by IARC. Its presence in drinking water has prompted regulatory monitoring under U.S. EPA UCMR3 and Method 522, which require quantitation at sub-µg/L levels to ensure public health protection.

Study Objectives and Overview

This work evaluated concurrent solvent recondensation–large volume splitless injection (CSR-LVSI) using an unmodified split/splitless GC inlet to lower reporting limits for 1,4-dioxane in drinking water without additional extract concentration.

Methodology

Drinking water samples were processed by activated charcoal SPE cartridges per EPA Method 522. Extracts (10 mL) were analyzed by directly injecting 10 µL via CSR-LVSI. A cool initial oven temperature (35 °C) and a deactivated retention gap focused solvent and analytes before column separation.

Instrumentation

• GC–MS: Agilent 7890A GC with 5975C quadrupole MSD (SIM mode)
• Autosampler: Agilent 7683 with 25 µL large-volume syringe
• Injector: Unmodified split/splitless inlet at 120 °C with wool-packed Restek liner
• Column: Rxi-624Sil MS (30 m × 0.25 mm × 1.40 µm) and 5 m retention gap
• Carrier gas: Helium at 1.4 mL/min constant flow
• Oven program: 35 °C (1 min) to 120 °C at 12 °C/min

Key Results and Discussion

• Linearity: R² > 0.999 over two calibration ranges down to 0.5 pg/µL (0.01 µg/L in water).
• Peak shape: Solvent recondensation yielded narrow, symmetric peaks.
• Analyte transfer: CSR-LVSI and standard injections of equivalent on-column mass produced comparable areas, indicating no loss.
• Interference control: SIM ions m/z 88 (quantitation) and m/z 58 (confirmation) were free from matrix co-elutions.
• Sensitivity: Signal-to-noise ≥10 at 10 pg on-column, enabling detection around 0.01 µg/L.
• Recoveries: 1,4-Dioxane and internal surrogate recoveries ranged 80–125%, compliant with Method 522 criteria.

Benefits and Practical Applications

• Enhanced sensitivity without specialized PTV injectors.
• Avoidance of solvent re-concentration, reducing analyte loss.
• Cost-effective implementation on existing GC–MS systems.
• Suitable for routine environmental monitoring and QA/QC laboratories.

Future Trends and Potential Applications

CSR-LVSI may be extended to other volatile or semi-volatile contaminants. Integration with high-resolution MS can enable non-target screening. Automated large-volume injection platforms and optimized retention gaps can further improve throughput, sensitivity, and method robustness.

Conclusion

CSR-LVSI implemented on an unmodified split/splitless inlet is a technically viable and economical approach to achieve sub-µg/L detection of 1,4-dioxane in drinking water. The method enhances chromatographic performance, meets regulatory limits, and simplifies sample preparation.

References

1. Grimmett, P.; Munch, J. Method Development for the Analysis of 1,4-Dioxane in Drinking Water Using Solid-Phase Extraction and Gas Chromatography-Mass Spectrometry. J. Chromatogr. Sci. 2009, 47, 31.
2. U.S. EPA. Unregulated Contaminant Monitoring Rule 3. http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/ucmr3; accessed 2012.
3. Wilson, B.; Wylie, P.; Klee, M. Large Volume Injection for Gas Chromatography Using a PTV Inlet. Agilent Technologies Appl. Note, 1997.
4. Magni, P.; Porzano, T. Concurrent Solvent Recondensation Large Sample Volume Splitless Injection. J. Sep. Sci. 2003, 26, 1491.
5. U.S. Pat. 6,955,709 B2.
6. Cochran, J. The Solvent Effect in Concurrent Solvent Recondensation Large Volume Splitless Injection with Methylene Chloride – EPA Method 8270 Semivolatiles. Restek ChromaBLOGraphy, 2011.
7. Misselwitz, M.; Cochran, J. Large Volume Splitless Injection Using an Unmodified Split/Splitless Inlet and GC-TOFMS for Pesticides and Brominated Flame Retardants. Restek Appl. Note EVAN1331-UNV, 2011.
8. Thermo Fisher Scientific. Use of a Novel Large Volume Splitless Injection Technique and Sequential Full Scan/SIM for Simultaneous Screen and Confirmation of Toxicological Specimens. Appl. Note 10014, 2007.
9. Thermo Fisher Scientific. Analysis of Pesticides and PCBs Using a Large Volume Splitless Injection Technique. Appl. Note 10013, 2004.
10. Thermo Fisher Scientific. 30X Increased Sensitivity in the Determination of PCBs in Water and Soil by GC-ECD Using Large Volume Splitless Technique. Appl. Note 10136, 2005.
11. Biedermann, M.; Fiscalini, A.; Grob, K. Large Volume Splitless Injection with Concurrent Solvent Recondensation: Keeping the Sample in Place in the Hot Vaporizing Chamber. J. Sep. Sci. 2004, 27, 1157.
12. U.S. EPA. Method 522, Determination of 1,4-Dioxane in Drinking Water by SPE and GC/MS with SIM. 2008.