• HI729113 is a titanium body, polymer-filled, double reference junction pH electrode with a Quick DIN connector. The flat-tip sensing portion of this electrode is made of general purpose glass. HI729113 also features a PTFE-type junction, as well as a built-in temperature sensor and amplifier in a single-probe design. This design consideration is ideal for measuring pH in boilers and cooling towers. HI729113 is designed for use with Hanna's HI99141 pH meter.

• Titanium alloy body

• Built-in temperature sensor

• Recessed flat tip

• Hanna Instruments offers a wide variety of pH electrodes designed for many different applications. The type of glass used to sense pH, bulb shape, body material, junction type, reference type, and the electrolyte used are just some of the design considerations.

• HI729113 uses general purpose (GP) glass, a flat-tip bulb, a titanium body, and a PTFE junction with polymer electrolyte.

General Purpose Glass Formulation

Measuring pH at very high temperatures is harmful to sensitive glass bulbs and shortens their lifespan. pH electrodes using general purpose (GP) glass have a resistance of 100 megohms at 25°C, while LT glass has a resistance of approximately 50 megohms at 25°C. As the temperature of the glass in the sample decreases, the resistance of LT glass will approach that of GP glass. If GP glass is used, the resistance will increase above the optimum range, causing increased impedance and ultimately affecting the measurement. HI729113 is suitable for samples from 0 to 80°C.

Flat-Tip Bulb

The recessed flat-tip bulb of HI729113 is easy to clean and prevents solids in the solution from collecting on the sensor. Other tip shapes include conical for penetration and spherical for water measurements.

Titanium Alloy Body

The titanium body enhances immunity to electrostatic and magnetic fields. It also has strong corrosion resistance, even in seawater.

Matching Pin

The matching pin is a differential measurement technique used to eliminate ground loops and common mode disturbances in the measurement system. In systems without a matching pin, currents in the sample can affect the voltage of the reference half-cell connected to the sample through the liquid junction. In this case, the reference electrode picks up electromagnetic fields, thereby altering the pH measurement. The matching pin isolates these currents/magnetic fields from the reference electrode. The HI729113 titanium body serves as a matching pin for safe and accurate pH measurement.

PTFE Junction

Porous polytetrafluoroethylene (PTFE) is a hydrophobic material with varying porosity. This type of junction is commonly used on electrodes with polymer electrolytes. Due to its chemical advantages, PTFE is widely used in industrial applications.

Quick DIN Connector

• HI729113 uses a Quick DIN connector. This type of connector is usually a proprietary connector for the supplied meter and may not be interchangeable. HI729113 is designed for use with Hanna's HI99141 pH meter. Other types of connectors include BNC, screw-type, T-type, and 3.5 mm, among others.

• Conventional electrodes are typically single junction. As shown in the figure above, these electrodes have only one junction between the internal reference wire and the external solution. Under adverse conditions such as high pressure, high temperature, highly acidic or alkaline solutions, the positive flow of electrolyte through the junction is often reversed, causing the sample solution to enter the reference chamber. If left unchecked, the reference electrode may become contaminated, leading to electrode failure. Another potential problem with single junction electrodes is junction clogging due to silver chloride (AgCl) precipitation. Silver readily precipitates in samples containing Tris buffer or heavy metals. When the electrolyte solution contacts the sample, some silver chloride precipitates on the outer surface of the junction. The result is drift in the sensor readings.

• As the name suggests, Hanna's double junction system has two junctions, as shown in the figure, only one of which contacts the sample. Under adverse conditions, the tendency for the sample to enter is evident. However, because the reference electrode system is physically separated from the intermediate electrolyte zone, contamination of the electrode is minimized. Since the external reference cell uses a “silver-free” fill solution, the double junction electrode also reduces the likelihood of junction clogging. Because silver is not present, no precipitate forms to clog the junction.