WTW SenTix 41 General-Purpose Liquid-Filled pH Electrode for Aqueous Solutions
| Brand | WTW |
|---|---|
| Origin | Germany |
| Model | SenTix 41 |
| Instrument Type | Portable |
| Parameter Type | Single-Parameter (pH) |
| pH Range | 0–14 |
| Temperature Range | −5 to +80 °C |
| Glass Membrane Impedance | 300 MΩ at 25 °C |
| Reference System | Gelified Internal Buffer (pH 7.0 ± 0.25) |
| Junction Type | Fibrous Diaphragm |
| Electrode Body Material | Noryl |
| Electrode Dimensions | Ø12 mm × 120 mm |
| Cable Length | 1 m |
| Connector Options | DIN or BNC |
| Integrated Temperature Sensor | NTC thermistor (30 kΩ) |
Overview
The WTW SenTix 41 is a robust, liquid-filled pH electrode engineered for reliable and reproducible measurements in routine aqueous sample analysis. Designed according to the principles of potentiometric pH determination via the Nernst equation, it employs a low-impedance pH-sensitive glass membrane coupled with a stable internal reference system. Its operational range spans the full aqueous pH scale (0–14) across a wide thermal envelope (−5 °C to +80 °C), making it suitable for field-deployable portable meters as well as benchtop laboratory systems. The electrode integrates a precision NTC temperature sensor (30 kΩ nominal resistance at 25 °C) to enable automatic temperature compensation (ATC), minimizing thermal drift and ensuring traceable measurement accuracy in compliance with ISO 7027 and ASTM D1293 guidelines for water quality testing.
Key Features
- Low-impedance glass membrane (300 MΩ at 25 °C) enabling rapid response even at sub-zero temperatures and improved signal stability in low-conductivity samples
- Gelified internal reference electrolyte (pH 7.0 ± 0.25) providing consistent junction potential and eliminating maintenance associated with refillable liquid electrolytes
- Fibrous diaphragm junction offering stable electrolyte outflow rate across temperature gradients—resistant to clogging during thermal cycling or particulate exposure
- Mechanically reinforced Noryl polymer housing rated for shock and vibration resistance per IEC 60068-2-64, supporting use in mobile environmental monitoring and industrial process verification
- Dual connector compatibility (DIN and BNC) ensures seamless integration with WTW handheld meters (e.g., MultiLine® SC, pH 3310), benchtop analyzers (e.g., inoLab® pH Level 2), and third-party instrumentation meeting IEC 62586-2 electrical interface standards
- Integrated NTC temperature sensor enables two-point calibration traceability and supports GLP-compliant data logging when paired with compliant meter firmware
Sample Compatibility & Compliance
The SenTix 41 is optimized for aqueous matrices including drinking water, surface water, wastewater effluents, boiler feedwater, and mild chemical process streams. It is not recommended for non-aqueous solvents, highly viscous media, or solutions containing sulfides, bromides, or high concentrations of heavy metals due to potential reference poisoning or membrane fouling. The electrode complies with key regulatory frameworks governing environmental and industrial water analysis: EN ISO 10523 (water quality — determination of pH), EPA Method 150.1, and DIN EN 27888. Its construction adheres to RoHS Directive 2011/65/EU and REACH Annex XVII restrictions on hazardous substances.
Software & Data Management
When used with WTW’s certified meter platforms (e.g., inoLab® series), the SenTix 41 supports full audit-trail functionality aligned with FDA 21 CFR Part 11 requirements—including electronic signature capture, user-level access control, and immutable calibration history storage. Data export is supported via USB or Bluetooth to WTW LabX® software (v3.5+), enabling automated report generation compliant with ISO/IEC 17025 documentation standards. Calibration verification logs include timestamp, operator ID, buffer lot numbers, slope (%), offset (mV), and temperature-corrected deviation metrics.
Applications
- Field-based monitoring of potable water distribution networks and groundwater wells
- In-process pH verification in food & beverage production (e.g., dairy pasteurization, brewing mash control)
- Environmental compliance testing under EU Water Framework Directive (2000/60/EC) reporting protocols
- Calibration and verification of online pH sensors in municipal wastewater treatment plants
- Educational laboratories requiring durable, low-maintenance electrodes for undergraduate electrochemistry instruction
- Pharmaceutical water system qualification (Purified Water, Water for Injection) per USP and EP 2.2.3
FAQ
What is the expected service life of the SenTix 41 under routine use?
With proper storage in KCl storage solution and periodic cleaning per WTW Technical Bulletin TB-021, typical operational lifespan exceeds 18 months in continuous daily use.
Can the SenTix 41 be used with non-WTW meters?
Yes—provided the instrument accepts standard DIN or BNC input impedance (≥1012 Ω) and supports external NTC temperature input per DIN 43760.
Is the electrode suitable for sterilization or autoclaving?
No—autoclaving exceeds the thermal rating and may compromise the gel electrolyte integrity and NTC calibration; chemical disinfection with 70% ethanol is permitted.
How often should calibration be performed?
Daily calibration is recommended for GLP/GMP environments; for routine field use, calibration before each sampling session and after every 2-hour continuous operation is advised.
Does the SenTix 41 meet IP67 ingress protection requirements?
The electrode body meets IP67 for dust and temporary immersion (1 m, 30 min); however, connector integrity depends on mating interface sealing—DIN connectors provide superior environmental sealing versus BNC in humid conditions.
