Zhuochi AOX-WK-S Microcoulometric Analyzer for Adsorbable Organic Halogens (AOX) per HJ 1214–2021

Overview

The Zhuochi AOX-WK-S Microcoulometric Analyzer is a dedicated instrumental system engineered to comply fully with the Chinese national standard HJ 1214–2021, “Determination of Adsorbable Organic Halogens (AOX) in Water — Microcoulometric Method.” This method is based on the quantitative electrochemical detection of halide ions released during high-temperature catalytic combustion of adsorbed organic halogen compounds. The system integrates thermal decomposition, selective adsorption, and microcoulometric titration into a single, closed-loop analytical workflow. It is designed for laboratories performing regulatory water quality monitoring—including municipal drinking water utilities, environmental testing agencies, wastewater treatment facilities, and third-party certification labs—requiring trace-level AOX quantification in accordance with nationally recognized method validation criteria.

Key Features

• Integrated dual-zone combustion furnace with precise airflow and temperature control (up to 950 °C), enabling complete pyrolysis of adsorbed organic halogen compounds while minimizing char formation and halogen loss.
• Dedicated quartz combustion tube optimized for consistent residence time and catalytic efficiency under inert gas flow (N₂ or O₂/N₂ mixture).
• Automated sample introduction mechanism supporting both solid-phase extraction (SPE) cartridges and pre-packed activated carbon columns, ensuring reproducible adsorption and transfer of AOX species.
• High-sensitivity microcoulometric detector with silver coulometric cell, calibrated against certified KBr standards; detection limit ≤ 1.0 µg/L AOX (as Cl) for 100 mL sample volume.
• Modular column adsorption unit compatible with standard 100–500 mg activated carbon cartridges, meeting HJ 1214–2021 requirements for carbon mass, flow rate, and breakthrough validation.
• Thermally stabilized gas delivery subsystem with mass flow controllers (MFCs) for carrier and oxygen gases, ensuring stoichiometric combustion and stable baseline response.
• Robust mechanical architecture with corrosion-resistant internal surfaces and integrated safety interlocks for overtemperature and gas leak protection.

Sample Compatibility & Compliance

The AOX-WK-S system accommodates a broad range of aqueous matrices defined in HJ 1214–2021, including surface water, groundwater, drinking water, industrial effluents, and treated wastewater. Sample pretreatment follows standardized procedures: acidification to pH ≤ 2.0, filtration through 0.45 µm membrane, and adsorption onto activated carbon under controlled flow (≤ 10 mL/min). The instrument supports method verification per HJ 1214–2021 Annex B, including recovery tests using 3-chlorophenol and 2,4-dichlorophenol reference standards, blank correction protocols, and ongoing calibration verification using certified AOX reference materials. While HJ 1214–2021 is a national Chinese standard, the underlying microcoulometric principle aligns with internationally recognized approaches such as DIN 38409-23, ISO 9562, and EPA Method 1650 (withdrawn but historically referenced for AOX methodology).

Software & Data Management

The analyzer operates via embedded firmware with USB-connected PC interface and proprietary acquisition software. The software provides real-time current integration, automatic endpoint detection, peak area calculation, and built-in calibration curve generation using multi-point standard additions. All raw data—including current vs. time traces, temperature profiles, gas flow logs, and user annotations—are stored in encrypted binary format with timestamping and operator ID tagging. Audit trail functionality complies with GLP principles: every parameter change, calibration event, and result export is logged with immutable metadata. Data export supports CSV and PDF report formats, suitable for inclusion in QA/QC documentation packages required by provincial ecological environment monitoring centers and CNAS-accredited laboratories.

Applications

• Regulatory compliance testing for AOX discharge limits under China’s “Emission Standards of Pollutants for Wastewater Treatment Plants” (GB 18918–2002) and local environmental protection bureau mandates.
• Process monitoring in pulp and paper mills, chlor-alkali plants, pharmaceutical manufacturing, and pesticide formulation facilities where chlorine-based reagents are used.
• Source water assessment for disinfection by-product (DBP) precursor screening prior to chlorination or chloramination.
• Method development and validation studies supporting inter-laboratory comparison programs organized by the Chinese National Institute of Metrology (NIM) or provincial environmental monitoring stations.
• Research applications investigating halogenated organic pollutant fate in aquatic systems, including sorption-desorption kinetics and biodegradation pathways.

FAQ

Does the AOX-WK-S meet international accreditation requirements such as ISO/IEC 17025?
Yes—the system supports full method validation per HJ 1214–2021, and its operational parameters, calibration traceability, and data integrity features align with ISO/IEC 17025:2017 clause 7.2 (method validation) and clause 7.7 (result reporting).
Can the system be used for AOX analysis in saline or high-TDS water samples?
HJ 1214–2021 specifies matrix interference mitigation steps, including dilution and use of isotopic internal standards where appropriate; the AOX-WK-S hardware design accommodates these adaptations with validated recovery performance up to 10 g/L total dissolved solids.
Is routine maintenance documented and supported with service manuals?
Zhuochi provides bilingual (Chinese/English) operation and maintenance manuals, preventive maintenance checklists, and certified technician training—available upon request for qualified laboratory personnel.