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

Importance of the Topic

Halogenated disinfection byproducts formed during water treatment pose significant health concerns due to their toxicity and prevalence in treated wastewater. Element specific detection of bromine and iodine in organic compounds is critical for monitoring and controlling these emerging contaminants.

Study Objectives and Overview

This study investigates the formation and transformation of volatile halogenated organic compounds in municipal wastewater following treatment with monochloramine. Using a gas chromatograph coupled to inductively coupled plasma mass spectrometry, the work aims to quantify bromine and iodine content via compound independent calibration derived from a standard dihaloaromatic compound.

Methodology and Instrumentation

• Sample preparation involved splitting wastewater samples into untreated and monochloramine treated aliquots, followed by extraction with methyl tertiary butyl ether.
• Calibration standards of 1-bromo-4-iodobenzene were prepared in MTBE at concentrations ranging from 0 to 100 ng/mL.
• Chromatographic separation was achieved on an HP-5 column with a pulsed splitless injection and temperature ramp from 37 °C to 260 °C.
• The ICP-MS was operated in time resolved acquisition mode for masses 79, 81 and 127 without collision gas, using a dry plasma at 700 W.

Key Results and Discussion

• Compound independent calibration curves for 127I and 81Br showed linear response over two orders of magnitude with low background interference.
• Treated samples exhibited a substantial increase in iodinated and brominated species, indicating formation of new disinfection byproducts.
• Certain unidentified organohalogen compounds decreased in concentration after chloramination, suggesting transformation into other halogenated products.
• Dry plasma conditions minimized oxide interferences and enabled interference free quantitation of halogens bound to organic molecules.

Benefits and Practical Applications of the Method

The GC-ICP-MS approach provides element specific sensitivity and compound independent quantitation for a broad range of halogenated organics. This technique complements traditional electron capture detection by distinguishing halogen content directly and allows determination of total volatile brominated and iodinated species in complex matrices.

Future Trends and Opportunities

Future work will integrate high resolution mass spectrometry for structural identification of unknown byproducts and explore optimized water treatment strategies to reduce toxic halogenated species. Broader application to diverse water sources and improved calibration protocols will enhance environmental monitoring and risk assessment.

Conclusion

GC-ICP-MS coupling offers a robust and sensitive platform for monitoring formation and transformation of volatile halogenated organic species in wastewater. The element specific analysis and compound independent calibration enable reliable quantitation and support efforts to understand and mitigate disinfection byproduct formation.

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