WTW OxiTop® IS/Control Series BOD Analyzer (Dilution Method & Mercury-Free Pressure Differential Method)
| Origin | Imported |
|---|---|
| Manufacturer Type | Authorized Distributor |
| Instrument Type | Laboratory BOD Analyzer |
| Measurement Principle | Pressure Differential (O₂ Consumption + CO₂ Absorption) |
| Measurement Range | 0–5000 mg/L |
| Detection Limit | 500 mg/L |
| Accuracy | ±1 mg/L |
| Single Sample Measurement Time | 8 min |
| Repeatability | ±3% |
| Compliance | DIN EN 1899-1, DIN EN 1899-2, EPA Method 5210B, GLP/GMP-ready |
Overview
The WTW OxiTop® IS and Control Series BOD Analyzers are engineered for precise, mercury-free biochemical oxygen demand (BOD) determination in municipal wastewater, drinking water, and environmental monitoring laboratories. These instruments implement the pressure differential method—based on microbial respiration kinetics in a sealed, temperature-controlled system—where dissolved oxygen consumption is quantified indirectly via pressure change resulting from O₂ depletion and concurrent CO₂ absorption by sodium hydroxide (NaOH) pellets. This principle eliminates mercury manometers and aligns with global regulatory trends toward non-toxic, maintenance-light instrumentation. The system operates at a strict 20 °C incubation temperature, complying with standardized 5-day BOD5 protocols defined in DIN EN 1899-1, DIN EN 1899-2, and EPA Method 5210B. Unlike classical dilution-based DO difference methods requiring manual probe calibration and frequent recalibration, the OxiTop® platform delivers fully automated, drift-compensated measurements with built-in thermal stabilization logic that delays initiation until thermal equilibrium is confirmed—ensuring measurement integrity across variable ambient lab conditions.
Key Features
- Mercury-free pressure differential detection using high-stability piezoresistive sensors with integrated temperature compensation
- Auto-thermal validation: OxiTop® sensor heads (green/yellow coded for inlet/outlet identification) monitor sample temperature continuously and defer measurement start until stable 20 °C is maintained for ≥60 minutes
- Configurable capacity: IS 6 and IS 12 models support simultaneous analysis of 6 or 12 samples; Control 6/12 systems scale to up to 100 sensors via IR remote control (OC100/OC110 handsets)
- Onboard data logging: Five daily snapshots stored automatically (one per day over 5 days), plus real-time access to current pressure trend and calculated BOD values
- GLP-compliant operation: Full audit trail capability when paired with Achat OC software (Order No. 208 990) and AK540/B interface cable (Order No. 902 842); supports 21 CFR Part 11–compatible electronic signatures via optional software configuration
- Modular expandability: Sensor heads compatible with OxiTop® PM standard calibration tablets for routine performance verification per ISO/IEC 17025 internal quality control requirements
Sample Compatibility & Compliance
The OxiTop® platform accommodates a broad spectrum of aqueous matrices—including raw sewage, treated effluent, surface water, and industrial process streams—without requiring filtration or pretreatment beyond standard homogenization. Sample volume is dynamically adjusted based on expected BOD concentration (e.g., lower volumes for high-BOD samples up to 5000 mg/L), minimizing dilution error and preserving microbial community integrity. All models meet statutory compliance for accredited environmental testing labs: DIN EN 1899-1 (dilution method reference), DIN EN 1899-2 (pressure differential method validation), and U.S. EPA Method 5210B. When used with inoLab® BSB/BOD 740 or ProfiLine Oxi 197i as complementary DO analyzers, full traceability across both dilution and pressure-differential workflows is achieved—supporting dual-method verification required under ISO 17025 clause 7.7.
Software & Data Management
Data acquisition and reporting are managed through two interoperable layers: embedded firmware logic within each sensor head and centralized software applications. The OC100/OC110 infrared remote controllers provide standalone visualization—including dynamic BOD curve plotting, statistical summaries (mean, SD, CV%), and auto-ID assignment—and enable wireless data transmission through glass incubator doors. For advanced analysis, Achat OC software imports raw pressure-time datasets, applies standardized BOD5 calculation algorithms per EN 1899-2 Annex C, and exports validated reports in PDF or CSV formats with embedded metadata (operator ID, timestamp, sensor serial number, calibration status). MultiLab® Pilot software extends functionality for inoLab®-based dilution workflows, enabling method library management (up to 7 user-defined dilution protocols), sample tracking (30 unique sample IDs × 18 dilutions each = 540 total configurations), and cross-platform synchronization with LIMS environments.
Applications
These analyzers serve critical roles across environmental compliance, wastewater treatment optimization, and research settings. Municipal utilities deploy OxiTop® Control systems for high-throughput influent/effluent BOD5 monitoring to verify nitrification/denitrification efficiency and adjust aeration rates. Regulatory laboratories use IS-series units for certified discharge reporting under EU Urban Wastewater Treatment Directive (91/271/EEC) and U.S. Clean Water Act NPDES permits. Academic and R&D facilities leverage the platform’s reproducibility (±3% RSD) and low detection limit (500 mg/L) for toxicity screening, biodegradability studies of novel surfactants or pharmaceuticals, and kinetic modeling of microbial respiration under varying carbon/nitrogen ratios. Integration with StirrOx® G self-stirring DO probes further enables hybrid workflows where pressure-differential results are cross-validated against direct DO depletion measurements.
FAQ
How does the pressure differential method differ from the classical dilution method?
The pressure differential method measures O₂ consumption indirectly via pressure drop in a sealed vial after CO₂ absorption; the dilution method relies on direct DO concentration measurement before and after 5-day incubation using electrochemical or optical DO probes.
Is temperature control external or built-in?
Temperature regulation is external—the OxiTop® sensors require placement inside a certified 20 °C incubator (e.g., WTW BOD Incubators); however, each sensor head autonomously verifies thermal stability prior to test initiation.
Can the system be validated for ISO/IEC 17025 accreditation?
Yes—routine verification using OxiTop® PM calibration tablets, combined with Achat OC’s audit-trail logging and electronic signature support, fulfills key technical requirements of ISO/IEC 17025:2017 clauses 7.7 (uncertainty estimation) and 8.9 (nonconforming work control).
What is the maximum number of samples per run with the Control system?
A single OC100/OC110 controller manages up to 100 OxiTop® sensor heads simultaneously, with automatic ID allocation and batch-level statistical reporting.
Does the instrument comply with FDA 21 CFR Part 11?
Native firmware does not include Part 11 controls, but Achat OC software (v3.2+) offers configurable electronic signatures, audit trails, and role-based access—enabling compliance when deployed in regulated pharmaceutical or biotech water testing environments.
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