Rapid Determination of Nitrobenzenes in Drinking Water Using Automated SPE with GC-ECD

Significance of the Topic

Nitrobenzene compounds are key intermediates in the manufacture of polyurethane, dyes, explosives, pesticides and pharmaceuticals. Their release into industrial effluents poses a threat to surface and groundwater sources used for human consumption. Regulatory bodies such as the U.S. EPA and IARC classify nitrobenzene and its derivatives as potential carcinogens, and national standards mandate low detection limits in drinking water. Reliable, sensitive analysis methods are therefore critical to protect public health and ensure regulatory compliance.

Study Objectives and Overview

This study presents a rapid, automated workflow for the extraction and quantification of fifteen nitrobenzene and nitroaromatic compounds in finished drinking water. The method follows Chinese Method HJ 648-2013 and U.S. EPA Method 8091 guidelines. Key aims include maximizing analyte recovery, improving reproducibility by automating solid-phase extraction (SPE), and achieving detection limits below 0.02 µg/L using gas chromatography with electron capture detection (GC-ECD).

Methodology and Instrumentation

The workflow uses a Thermo Scientific Dionex AutoTrace 280 SPE system to automate cartridge conditioning, sample loading, rinsing and elution steps. A Hypersep Retain PEP cartridge (divinylbenzene/polyvinylpyrrolidone phase) is conditioned sequentially with methanol, ethyl acetate and n-hexane, followed by loading 500 mL of water sample spiked with internal standards. After a rinse with water, analytes are eluted in 10 mL of n-hexane/acetone (9:1), dried over anhydrous sodium sulfate and concentrated.

The concentrated extracts are analyzed on a Thermo Scientific TRACE 1310 GC equipped with an Instant Connect split/splitless injector and an electron capture detector. A mid-polarity TraceGOLD TG-1701MS column (30 m × 0.25 mm × 0.25 µm) delivers baseline separation of all 15 analytes in under 30 minutes using a temperature program from 50 °C up to 250 °C under constant nitrogen flow.

Key Results and Discussion

Calibration over 5–100 µg/L yields correlation coefficients (R2) above 0.99 for all compounds. Method detection limits range from 0.02 to 2 µg/L, with most analytes at 0.1 µg/L or below. Spike recoveries at 0.02, 0.1 and 0.5 µg/L average between 81% and 98%, and intra-day reproducibility (RSD, n=3) remains below 9%. Representative chromatograms demonstrate clear resolution of all target analytes without matrix interferences. Application to river water samples detected 2,4-dinitrochlorobenzene at 0.137 µg/L, illustrating method suitability for real-world monitoring.

Benefits and Practical Applications

• Automation reduces manual intervention and variability, improving throughput and data consistency.
• Low method detection limits support compliance monitoring in drinking water supplies.
• Short extraction and analysis times (≈50 min SPE, <30 min GC run) enable high sample throughput.
• Robust performance across a broad panel of nitrobenzene derivatives addresses diverse regulatory requirements.

Future Trends and Potential Applications

Advances in on-line SPE coupled directly to GC-ECD or GC-MS could further streamline workflows. Development of greener sorbents and solvents will reduce environmental impact. High-throughput screening using multiplexed SPE systems and automated data processing with machine learning promises rapid decision support for water quality management. Integration with portable GC-ECD units may facilitate in-field monitoring at treatment plants and distribution networks.

Conclusion

The automated SPE-GC-ECD approach delivers sensitive, precise and rapid determination of fifteen nitrobenzene compounds in drinking water. By integrating the AutoTrace 280 SPE system with TRACE 1310 GC-ECD, the method achieves low detection limits, excellent recoveries and high reproducibility, meeting stringent international regulatory standards for water monitoring.

References

1. U.S. Environmental Protection Agency. Nitrobenzene Quickview (CASRN 98-95-3), IRIS Database.
2. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Volume 1–110, International Agency for Research on Cancer.
3. GB 5749-2006. Hygiene Standards for Drinking Water Quality. Chinese Ministry of Environmental Protection.
4. HJ 648-2013. Water Quality—Determination of Nitroaromatics by GC. Chinese Ministry of Environmental Protection.
5. U.S. EPA Method 8091. Nitroaromatics and Cyclic Ketones by GC with ECD.