An Examination of the Presence, Formation, and Transformation of Volatile Halogenated Organic Species in Wastewater Extracts Using GC-ICP-MS

Significance of the Topic

The formation of halogenated disinfection byproducts (DBPs) during wastewater treatment poses significant human health risks, particularly for brominated and iodinated species that exhibit higher toxicity. With increasing reliance on wastewater reuse and desalination, rapid, element-specific screening methods are essential to monitor and control these emerging contaminants.

Objectives and Study Overview

This study aimed to investigate the presence, formation, and transformation of volatile halogenated organic compounds in municipal wastewater before and after treatment with monochloramine. An Agilent 7890A GC coupled to an Agilent 7700x ICP-MS was employed with compound-independent calibrations (CICs) based on 1-bromo-4-iodobenzene to quantify bromine and iodine across unknown species.

Methodology and Instrumentation

Municipal wastewater samples were split into untreated and monochloramine-treated aliquots (0.08 mM, 4 h reaction). Each 35 mL sample was extracted with 5 mL MTBE following a modified EPA 551.1 protocol. GC separation used an HP-5 column (30 m×0.32 mm, 0.25 µm), pulsed splitless injection (1 µL), and a temperature program from 37 °C to 260 °C. The ICP-MS operated in time-resolved analysis mode for masses 79, 81, and 127 without collision gas.

Used Instrumentation

• Agilent 7890A gas chromatograph
• Agilent 7700x ICP-MS
• Agilent J&W HP-5 column, 30 m×0.32 mm, 0.25 µm
• Helium carrier gas, pulsed splitless injection
• RF power 700 W, argon dilution gas 0.39 L/min
• Calibration standard: 1-bromo-4-iodobenzene in MTBE (1–100 ng/mL)

Main Results and Discussion

• Linear calibration over 1–100 ng/mL for 127I and 81Br with minimal background (~30 cps) and low XeH⁺ interferences.
• Baseline halogenated organics were present in untreated samples; chloramination caused a dramatic increase in most brominated and iodinated species and generated new DBPs.
• Certain unidentified species (Br-2, I-3) decreased after treatment, indicating selective transformation pathways.
• Dry plasma conditions and lower RF power suppressed argon-based interferences, enabling sensitive, interference-free halogen detection.

Benefits and Practical Applications

• Element-specific detection distinguishes halogenated compounds in complex mixtures.
• Compound-independent calibration permits approximate quantification of unknown DBPs.
• Rapid screening supports water quality monitoring and regulatory compliance.

Future Trends and Applications

Future work will integrate GC-ICP-MS with high-resolution mass spectrometry (GC-Q-TOF) to structurally identify unknown DBPs and explore optimized treatment strategies that minimize formation of toxic brominated and iodinated byproducts. The platform may be extended to other environmental matrices and disinfection processes.

Conclusion

The combination of Agilent 7890A GC and 7700x ICP-MS with compound-independent calibrations provides a robust, high-sensitivity method for detecting, quantifying, and tracking the transformation of volatile halogenated organics in wastewater. This approach enhances element specificity, reduces interferences, and offers a powerful tool for managing DBP formation in water treatment.

Reference

1. Richardson SD, Ternes TA. Occurrence and Mammalian Cell Toxicity of Iodinated Disinfection Byproducts in Drinking Water. Environ Sci Technol. 2008;42:8330–8338.
2. Sharma VK, Zboril R, McDonald TJ. Formation and toxicity of brominated disinfection byproducts during chlorination and chloramination of water: A review. J Environ Sci Health B. 2013;49:212–228.
3. Hua G, Reckhow DA. Effect of pre-ozonation on the formation and speciation of DBPs. Water Res. 2013;47:4322–4330.
4. Jeong CH, et al. Occurrence and Toxicity of Disinfection Byproducts in European Drinking Waters in Relation with the HIWATE Epidemiology Study. Environ Sci Technol. 2012;46:12120–12128.
5. United States EPA. National primary drinking water regulations: Stage 2 disinfectants and disinfection byproducts rule. Fed Regist. 2006;71:387–493.
6. Krasner SW, et al. Occurrence of a New Generation of Disinfection Byproducts. Environ Sci Technol. 2006;40:7175–7185.
7. Smith EM, et al. Comparison of Byproduct Formation in Waters Treated with Chlorine and Iodine: Relevance to Point-of-Use Treatment. Environ Sci Technol. 2010;44:8446–8452.
8. Woo YT, et al. Use of Mechanism-Based Structure-Activity Relationships Analysis in Carcinogenic Potential Ranking for Drinking Water Disinfection By-Products. Environ Health Perspect. 2002;110(Suppl 1):75–82.