Analysis of halogen-specific TOX revisited: Method improvement and application

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Water Quality Analysis

Background:

• Total organic halogen (TOX) is a key indicator of water contamination.
• Existing methods for TOX analysis have limitations in sensitivity and scope.
• Understanding the formation of specific halogenated disinfection byproducts (DBPs) is crucial for public health.

Purpose of the Study:

• To optimize and validate a robust method for analyzing total organic halogen (TOX) in drinking water.
• To investigate the formation of halogen-specific TOX during water treatment and disinfection processes.
• To assess the contribution of various halogenated DBPs to overall TOX levels.

Main Methods:

• Adsorption of organic halogens onto activated carbon.
• Combustion of activated carbon and adsorbed material.
• Absorption of resulting hydrogen halide gases and analysis via on-line ion chromatography.
• Method validation including detection limits and recovery studies.

Main Results:

• Achieved method detection limits of 5µgL⁻¹ for TOCl, 2µgL⁻¹ for TOBr, and 2µgL⁻¹ for TOI.
• Demonstrated excellent method recoveries for a range of model compounds.
• Observed up to 70% conversion of bromide to TOBr during plant disinfection.
• Found preferential formation of TOI in chloraminated samples, with trihalomethanes comprising ≤20% of TOX.

Conclusions:

• The optimized method offers significant improvements for analyzing halogen-specific TOX in drinking water.
• The study highlights the formation of non-trihalomethane halogenated DBPs, often not routinely measured.
• This research provides a comprehensive assessment of TOX analysis and its application in understanding DBP formation.