WTW SenTix 81 precision pH electrode, glass shaft, refillable, 103642

WTW lists a wide range of applications for these glass electrodes: from diluted acids and emulsions through to beer, milk and fruit juice, right up to serum and urine. The WTW SenTix 81 features a glass shaft, a refillable liquid electrolyte and a platinum wire junction. It measures from 0 to 14 pH at sample temperatures of 0 to 100 °C. An NTC temperature sensor (30 kΩ) is fitted.

Platinum wire junction and conical membrane

The glass shaft is 120 mm long and has a diameter of 12 mm. According to WTW, the platinum wire junction ensures optimum electrolyte flow without blockages. The membrane is conical in shape; according to WTW, it is impact-resistant and easy to clean. The membrane resistance at 25 °C is less than 600 MΩ. The reference system is 3 mol/l KCl, Ag+-free and refillable. According to WTW, the liquid electrolyte enables fast response times.

Typical applications, according to WTW

• Diluted acids, salt solutions, emulsions and suspensions
• Cooling water, dye solutions and electroplating baths
• Drinking water, groundwater, swimming pool water, lake water, surface water and seawater
• Soil, paper and coffee extracts
• Beer, lemonade, fruit juice, vegetable juice, wine, mineral water, milk and vinegar
• Hair dye, mouthwash and household cleaners
• Enzyme solutions, gastric juice, infusion solutions, protein-containing liquids, serum, Tris buffer solutions and urine (pharmaceuticals, biology, medicine)

Connection

The SenTix 81 has a permanently attached 1 m cable with a waterproof DIN plug (DIN 19262) and a 4 mm banana plug for the sensor. The variants in this series differ only in terms of plug, cable and temperature sensor; the electrode itself is identical. The choice therefore depends on the input of the measuring instrument. If a longer shaft is needed, the SenTix 91 has a length of 170 mm instead of 120 mm.

Refilling and storage

The refill opening remains open during calibration and measurement. A dropper bottle is included, according to the WTW instructions. For short measurement breaks, the electrode is immersed in reference electrolyte (KCl 3 mol/l, Ag+-free) with the refill opening open. Overnight and for longer periods, it stays in the wetting cap, filled with reference electrolyte, with the refill opening closed. According to WTW, storing the electrode in a dry state or in deionised water can cause permanent damage. If the cap has dried out, the electrode needs at least 24 hours in reference electrolyte. As with any pH electrode, strong acids and alkalis, hydrofluoric acid, organic solvents, oils, fats and proteins shorten its service life.

Technical details

Scope of delivery

• 1 WTW SenTix 81 pH electrode with wetting cap
• Dropper bottle for refilling (included according to the WTW instructions)
• 1 m fixed cable with DIN and banana plugs, permanently attached to the electrode

Accessories and procurement service

Reference electrolyte KCl 3 mol/l for refilling and buffer solutions for calibration are also available. If you require a different version or multiple electrodes, please enquire via the procurement service.