Fast analysis of AOX in waters by CIC

Significance of the topic

Monitoring adsorbable organically bound halogens (AOX) and adsorbable organically bound fluorine (AOF) is critical for safeguarding water quality and public health. Many organohalogen compounds and their degradation products pose environmental and toxicological risks. A reliable, rapid analytical approach ensures efficient tracking of contamination sources and verification of treatment processes.

Objectives and Study Overview

The study presents a validated combustion ion chromatography (CIC) procedure aligned with DIN 38409-59 for simultaneous determination of AOCl, AOBr, AOI, their sum parameter CIC-AOX(Cl), and AOF. It aims to enhance sensitivity, specificity, and throughput compared to classical microcoulometric titration methods.

Methodology and Instrumentation

Sample preparation involves preconcentration via adsorption on activated carbon columns under controlled pH conditions: acidification (pH <2) for AOX fractions with nitric acid, and neutralization with sodium nitrate for AOF. The semi-automated APU sim system processes up to six samples in parallel. Adsorbents are transferred to ceramic boats for pyrohydrolytic combustion above 950 °C in an argon/oxygen atmosphere. Volatilized halogens are trapped in ultrapure water via the 920 Absorber Module and quantified by ion chromatography on a Metrosep A Supp 5 - 250/4.0 column with A Supp 5 Guard/4.0, using suppressed conductivity detection. Automated calibration and repeat injections utilize MiPT and intelligent MagIC Net software, supported by Dosino dosing units.

Key Results and Discussion

Blank values were minimal (fluoride 1.1 μg/L; chloride 2.6 μg/L), with limits of detection (LOD) of 0.38 μg/L for F, 1.36 μg/L for Cl, 0.24 μg/L for Br, and 0.47 μg/L for I, meeting or exceeding DIN 38409-59 requirements. Separation times were under 7 minutes for fluoride and 25 minutes for other halides. The method enables precise quantification of individual halogen fractions alongside the aggregate AOX parameter, validated across multiple laboratories.

Benefits and Practical Applications

• Enhanced sensitivity and selectivity for individual halogen species and PFAS monitoring.
• Fully automated workflow reduces manual handling, improves repeatability, and supports 24/7 operation.
• Single-manufacturer configuration simplifies maintenance and ensures compatibility.
• Applicable in research, routine QA/QC, regulatory compliance, and industrial process control.

Future Trends and Applications

Emerging developments may include integration with advanced data analytics and laboratory information management systems, miniaturized combustion modules for portable analysis, coupling with high-resolution mass spectrometry for structural identification, and expansion of the method to other organometallic or emerging contaminants.

Conclusion

The DIN 38409-59 compliant CIC approach delivers a robust, high-throughput solution for comprehensive assessment of AOX fractions and AOF. Its automated, standardized protocol offers significant gains in sensitivity, accuracy, and operational efficiency for water analysis laboratories.

Instrumental Setup

• Combustion IC Manual – Quartz (2.930.9030) with Combustion Oven TEI (2.0136.0600) and quartz tube (6.07311.100).
• 920 Absorber Module and 930 Compact IC Flex Oven/SeS/PP/Deg with MagIC Net software.
• APU sim system for adsorption; Auto Boat Drive and MMS 5000 autosampler (Analytik Jena).
• Metrosep A Supp 5 - 250/4.0 (6.1006.530) and A Supp 5 Guard/4.0 (6.1006.500).
• MiPT partial-loop injection accessory (6.5330.180) and 858 Professional Sample Processor Pump (2.858.0020).

References

1. Xu R.; Xie Y.; Tian J.; et al. Adsorbable Organic Halogens in Contaminated Water Environment: A Review of Sources and Removal Technologies. J Clean Prod 2021, 283.
2. Müller G. Sense or No-Sense of the Sum Parameter for Water Soluble “Adsorbable Organic Halogens” (AOX) and “Absorbed Organic Halogens” (AOX-S18) for the Assessment of Organohalogens in Sludges and Sediments. Chemosphere 2003, 52(2), 371–379.
3. Dann A.B.; Hontela A. Triclosan: Environmental Exposure, Toxicity and Mechanisms of Action. J Appl Toxicol 2011, 31(4), 285–311.
4. Xie Y.; Chen L.; Liu R. AOX Contamination Status and Genotoxicity of AOX-Bearing Pharmaceutical Wastewater. J Environ Sci 2017, 52, 170–177.