WTW CR 3200 COD Digestion System (Model 1P22-1)

Overview

The WTW CR 3200 COD Digestion System (Model 1P22-1) is a precision-engineered thermal digestion unit designed for standardized chemical oxygen demand (COD) analysis in accordance with ISO 6060, DIN 38409-41, and EPA Method 410.1. It employs resistive heating within a high-thermal-conductivity aluminum block to deliver rapid, uniform, and reproducible temperature profiles across all 24 sample positions. Unlike open-bath or ceramic plate digesters, the CR 3200’s monolithic single-block architecture minimizes thermal gradient deviation (<±0.8 °C between adjacent positions at 150 °C), ensuring compliance with GLP requirements for inter-sample comparability. The system operates exclusively in the closed-tube digestion mode—optimized for Hach, Merck, and other standard 16 mm OD COD vials—eliminating evaporative loss and enabling safe, hands-free operation during extended heating cycles up to 180 minutes.

Key Features

• 24-position digestion block accommodating standard 16 mm outer diameter reaction tubes (e.g., Hach TNTplus vials, Merck Spectroquant® tubes)
• Microprocessor-controlled temperature regulation from 25 °C to 170 °C in precise 1 °C increments, with real-time LED display and status indicators
• Predefined digestion protocols aligned with common regulatory methods: 148 °C/120 min (ISO 6060), 120 °C/30–120 min (DIN 38409-41), and 100 °C/60 min (low-COD wastewater screening)
• Eight user-programmable methods supporting custom temperature–time combinations (25–170 °C, 0–180 min), stored non-volatile memory
• Auto-start functionality triggered upon lid closure; automatic power-down after program completion with audible end-of-cycle signal
• Integrated thermal shielding and overtemperature cut-off (185 °C safety limit) compliant with DIN VDE 0700 Part 1 (Class I insulation)
• RS232 interface for external logging or integration into LIMS environments; dual banana sockets support optional calibrated external temperature monitoring (e.g., TFK CR probe, P/N 250100)

Sample Compatibility & Compliance

The CR 3200 is validated for use with sealed, borosilicate glass or quartz reaction vessels rated for pressures up to 2 bar at 170 °C. Its geometry accommodates both standard 16 mm OD vials and tapered-bottom variants without adapter requirements. All factory-set programs reflect method-specific ramp-and-hold profiles required by ISO, DIN, and ASTM D1252 standards. The instrument meets electromagnetic compatibility (EMC) requirements per EN 61326-1 and carries CE, cETLus, and GS marks—certifying conformity with EU Machinery Directive 2006/42/EC and Low Voltage Directive 2014/35/EU. For regulated laboratories, the system supports audit-ready operation when paired with optional TFK CR temperature verification probes traceable to DKD/DAkkS calibration standards.

Software & Data Management

While the CR 3200 operates as a standalone benchtop unit, its RS232 port enables bidirectional communication with host PCs running WTW LabX™ Lite or third-party SCADA/LIMS platforms via ASCII protocol. Logged data includes start time, setpoint, actual block temperature (sample-average), elapsed duration, and end status. When used with the TFK CR probe, real-time temperature feedback allows validation of thermal homogeneity across the block—critical for FDA 21 CFR Part 11-compliant workflows where electronic records require attributable, legible, and contemporaneous data capture. No proprietary software installation is required; terminal emulation (e.g., PuTTY, Tera Term) suffices for raw data export in CSV-compatible format.

Applications

• Routine COD determination in municipal and industrial wastewater treatment plants
• Environmental monitoring labs performing compliance testing per national discharge permits
• Research laboratories evaluating organic load in surface water, groundwater, and effluent streams
• Educational institutions conducting standardized water chemistry experiments under ISO/ASTM guidelines
• QA/QC departments validating digestion efficiency prior to spectrophotometric or titrimetric quantification

FAQ

Is the CR 3200 compatible with Hach TNTplus vials?

Yes—the 24-position block is dimensionally optimized for Hach’s 16 mm OD TNTplus series (e.g., TNT820, TNT821) and equivalent Merck Spectroquant® tubes.
Can the instrument be used for total phosphorus or total nitrogen digestion?

The CR 3200 is specifically engineered and validated for COD applications. While it may reach temperatures required for some TP/TN methods, WTW does not certify or support such use due to differing pressure, ramp rate, and hold-time specifications.
What is the typical heating stabilization time to 148 °C?

Approximately 10 minutes from ambient (25 °C), verified per DIN EN ISO/IEC 17025 calibration procedures using NIST-traceable thermocouples.
Does the system include a temperature calibration certificate?

No—calibration is performed at the factory per internal QA protocol. Users must perform periodic verification using an accredited external probe (e.g., TFK CR); documentation templates for calibration logs are available upon request.
Is remote monitoring supported via Ethernet or Wi-Fi?

No—the CR 3200 provides only RS232 serial output. Network connectivity requires an external RS232-to-Ethernet converter configured separately.