Zhuochi AOX-WK-S Microcoulometric Analyzer for Adsorbable Organic Halogens (AOX) in Paper Products per GB/T 34845-2017

Overview

The Zhuochi AOX-WK-S Microcoulometric Analyzer is a dedicated instrumental system engineered to quantify adsorbable organic halogens (AOX) in consumer paper products—including tissue, towel, and hygiene papers—in strict accordance with the Chinese national standard GB/T 34845-2017, “Water Quality—Determination of Adsorbable Organic Halogens (AOX)—Microcoulometric Method.” The system operates on the principle of high-temperature catalytic combustion followed by microcoulometric titration: samples are pyrolyzed under controlled oxygen flow at temperatures between 500 °C and 1000 °C, converting organically bound chlorine, bromine, and iodine into halide ions (X⁻). These ions are absorbed in an aqueous electrolyte solution and quantified via electrochemical detection using a silver/silver chloride coulometric cell, where the charge required to regenerate Ag⁺ is directly proportional to halogen mass. This method delivers trace-level sensitivity and high reproducibility essential for regulatory compliance testing in pulp, paper, and packaging manufacturing quality control laboratories.

Key Features

• Integrated dual-zone combustion furnace with precision gas-flow–controlled temperature regulation (±1% ±5 °C), enabling stable thermal decomposition across the full 500–1000 °C operating range.
• Dedicated quartz combustion tube optimized for complete oxidation of cellulose-based matrices without char residue or halogen loss.
• Automated sample introduction and ash removal modules minimizing operator intervention and cross-contamination risk.
• High-sensitivity microcoulometric detector with real-time charge integration, calibrated against certified KCl standards traceable to NIM (National Institute of Metrology, China).
• On-board column adsorption unit featuring activated carbon cartridges pre-conditioned per GB/T 34845-2017 specifications for selective AOX enrichment from aqueous extracts.
• Rugged industrial-grade architecture designed for continuous operation in ISO/IEC 17025-accredited environmental testing labs.

Sample Compatibility & Compliance

The AOX-WK-S system is validated for solid-phase paper samples requiring extraction prior to analysis. Per GB/T 34845-2017, paper specimens are first extracted with neutral water or dilute NaOH, followed by adsorption of AOX onto activated carbon columns. Eluted halides are then introduced into the combustion–microcoulometric workflow. The analyzer meets all procedural and performance requirements outlined in the standard, including calibration verification, blank correction protocols, and recovery validation (≥80–110%). While GB/T 34845-2017 is a national standard, its methodology aligns closely with internationally recognized AOX determination principles found in DIN 38409-23, EPA Method 1650, and ISO 9562. System documentation supports GLP-compliant audit trails when paired with validated laboratory information management systems (LIMS).

Software & Data Management

The analyzer includes embedded firmware with intuitive touchscreen interface for method setup, real-time signal monitoring, and automatic peak integration. Raw coulometric current curves, temperature profiles, and calibration logs are exportable in CSV format for secondary processing. All quantitative results include metadata: sample ID, date/time stamp, operator ID, calibration status, and instrument serial number—supporting traceability requirements under CNAS-CL01 and facilitating alignment with FDA 21 CFR Part 11 when integrated into validated IT environments. Audit trail functionality records all parameter modifications, result edits, and user logins, ensuring data integrity throughout the analytical lifecycle.

Applications

• Quality assurance of bleached and unbleached tissue, napkin, and sanitary paper products for AOX content prior to market release.
• Process optimization support for pulp mills evaluating chlorine-free (TCF) or elemental chlorine-free (ECF) bleaching sequences.
• Regulatory submission testing for manufacturers supplying into markets requiring AOX declarations (e.g., EU Ecolabel, Nordic Swan).
• Research applications investigating halogen migration from recycled fiber or functional additives (e.g., flame retardants, biocides) into paper substrates.
• Environmental compliance monitoring for wastewater effluents generated during paper production—when adapted per GB/T 15959 or ISO 9562 protocols.

FAQ

What sample types does the AOX-WK-S support beyond paper products?
The system is configured per GB/T 34845-2017 for paper, but its combustion–microcoulometric core can be adapted for solid matrices such as sludge, soil, and plastics following validated extraction and clean-up procedures.
Is the instrument compliant with international AOX standards like ISO 9562 or EPA 1650?
While hardware and detection principles are compatible, formal compliance requires method adaptation and lab-specific validation per each standard’s procedural requirements; GB/T 34845-2017 alignment is fully verified.
Does the system provide full audit trail and electronic signature capability?
Yes—firmware logs all critical events; full 21 CFR Part 11 compliance requires integration with a validated LIMS or ELN platform.
What maintenance intervals are recommended for the combustion tube and coulometric cell?
Quartz combustion tubes should be inspected after every 50 analyses and replaced if discoloration or cracking occurs; coulometric cells require electrolyte replacement every 30 days or 200 injections, whichever comes first.
Can the AOX-WK-S quantify individual halogens (Cl, Br, I) separately?
No—it reports total AOX as chloride-equivalent mass; speciation requires coupling with IC-MS or HR-GC/MS techniques.