Shenchanghong CN-201 COD & Ammonia Nitrogen Analyzer

Overview

The Shenchanghong CN-201 COD & Ammonia Nitrogen Analyzer is a dual-parameter benchtop laboratory instrument engineered for precise, trace-level quantification of chemical oxygen demand (COD) and ammonia nitrogen (NH₃-N) in aqueous environmental samples. It implements standardized colorimetric methodologies: dichromate-based oxidation at 165 °C for COD determination (ISO 6060, APHA 5220 C), and Nesslerization at controlled alkaline pH for ammonia nitrogen (ISO 7150-1, APHA 4500-NH₃ B). The system decouples digestion and photometric measurement—eliminating thermal crosstalk between the heating module and optical path—to ensure long-term baseline stability and metrological integrity. Designed for compliance with routine water quality monitoring protocols, the CN-201 supports regulatory reporting under national environmental standards (e.g., China’s HJ 828–2017 for COD; HJ 535–2009 for NH₃-N) and serves as a validated platform for method verification in GLP-aligned laboratories.

Key Features

• Optically isolated architecture: Independent analyzer and DIS-16B digestion unit prevent heat-induced drift in absorbance readings.
• Cold-light, narrow-band interference optical system with dual-wavelength capability (610 nm for standard COD, 420 nm for low-range COD and NH₃-N), ensuring high spectral selectivity and minimal matrix interference.
• 3.5-inch full-color touch screen on the DIS-16B digester (320 × 240 resolution) with bilingual UI (English/Chinese), real-time temperature profiling, and programmable ramp-hold profiles.
• Integrated safety controls: Dual thermal protection (automatic cutoff at 200 °C), audible digestion-end alert, and post-digestion auto-shutdown.
• Calibration robustness: Multi-point non-linear calibration with zero-error interpolation at user-defined setpoints—compensating for inherent thermistor nonlinearity in conventional digesters.
• Data retention: Stores up to 20 preloaded calibration curves and 199 measurement records with non-volatile memory; retains all data during power interruption.
• Durable construction: Mainframe housing molded from ABS polymer with enhanced resistance to acid vapors, organic solvents, and humid laboratory environments.

Sample Compatibility & Compliance

The CN-201 accepts standard 16-mm borosilicate glass digestion tubes (included), compatible with both open-reflux and sealed-tube digestion protocols. It accommodates raw and pretreated samples from surface water, wastewater effluents, industrial discharges, and potable water sources—with chloride tolerance up to 2000 mg/L Cl⁻ (via mercury sulfate masking per Standard Methods 5220 D). The instrument meets mechanical and electrical safety requirements per IEC 61010-1:2010 and supports traceability in regulated environments through audit-ready operation logs. While not inherently 21 CFR Part 11 compliant, its deterministic calibration workflow, fixed wavelength selection, and immutable result storage align with ALCOA+ principles for data integrity in environmental QA/QC labs.

Software & Data Management

No external PC software is required for basic operation; all configuration, calibration, and reporting occur via the embedded interface. The analyzer supports manual curve entry or factory-default polynomial fits for both parameters. Measured values are displayed in real time with %RSD calculation for replicate runs. Export is limited to on-device review and print-ready reports (via optional serial-to-printer adapter); for LIMS integration, users may manually transcribe results using the alphanumeric LCD display (240 × 128 pixels, Chinese/English font). Firmware updates are performed via USB flash drive, with version history and checksum verification built into the bootloader.

Applications

• Regulatory compliance testing for municipal wastewater treatment plants (WWTPs) and industrial discharge monitoring per local environmental protection bureau mandates.
• Academic research in limnology, biogeochemistry, and environmental engineering where parallel COD/NH₃-N trends inform nutrient loading assessments.
• Quality control in drinking water utilities performing source water screening and distribution system integrity checks.
• Method validation studies comparing rapid digestion protocols against classical reflux methods (e.g., ASTM D1252–05).
• Educational laboratories requiring robust, service-resistant instrumentation for undergraduate analytical chemistry and environmental science curricula.

FAQ

What digestion method does the CN-201 use for COD analysis?

It employs closed-tube dichromate oxidation at 165 °C for 15 minutes, conforming to HJ 828–2017 and ISO 6060.
Can the instrument measure both COD and NH₃-N simultaneously?

No—measurements are sequential. Users must select the target parameter before digestion and analysis; optical filters are manually switched between 610 nm and 420 nm wavelengths.
Is the CN-201 suitable for field use?

It is designed exclusively for laboratory environments: AC-powered, non-battery-operated, and requires stable ambient conditions (5–40 °C, no direct sunlight or vibration).
How is calibration verified across the measurement range?

Using certified reference materials (CRMs) traceable to NIM (China National Institute of Metrology); multi-point calibration eliminates systematic offset at critical thresholds (e.g., 5 mg/L and 2000 mg/L COD).
Does the system support GLP-compliant audit trails?

It maintains chronological logs of calibration events and measurement timestamps but lacks electronic signature, user-role access control, or automated report generation required for full GLP/GMP compliance.