Product Overview

• HI1332B is a PEI body double junction pH electrode with BNC connector. The electrode has a ceramic junction in the outer reference cell, and the pH sensing portion is made of general purpose glass, protected by an extension of the durable PEI body.

• This design consideration makes it ideal for chemicals, quality control, field applications, and general purpose use.

• Durable PEI body

• Double junction design

• Refillable electrode

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

The HI1332B uses general purpose (GP) glass, a spherical bulb, a polyetherimide (PEI) body, a single ceramic frit, and a double junction.

Figure 1 details:

• General purpose glass formulation

• Measuring pH at very high temperatures is harmful to the sensitive glass bulb and shortens its life. A pH electrode with general purpose (GP) glass has a resistance of 100 megohms at 25C, while LT glass has a resistance of approximately 25 megohms at 50C. 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. The HI1332B is suitable for samples with a measurement range of 0 to 70C.°°°

Figure 2 details:

• Spherical bulb

• Spherical bulbs are used for general purpose applications. Other tip shapes include conical for penetration and flat tips for surface measurements.

Figure 3 details:

• PEI body

• The body of the HI1332B is composed of polyetherimide (PEI) resin. The PEI body is suitable for a wide range of applications and, due to its durability, performs excellently in field measurements. The shield around the spherical glass tip minimizes damage from accidental impact or dropping of the electrode. PEI plastic is a high-quality plastic that is chemically resistant to many harsh chemicals.

Figure 4 details:

• Double junction reference

• A double junction electrode has an internal compartment surrounding the reference wire. Silver ions are present in the electrolyte of the internal compartment that houses the Ag/AgCl reference wire; the electrolyte outside this compartment is silver-free. The double junction design means that virtually no silver from the electrode enters the sample. This design allows measurement in applications where silver ions in the sample are undesirable or where silver precipitates may form on the junction.

Figure 5 details:

• BNC connector

• The HI1332B uses a BNC connector. This type of connector is universal in that it can be used with any pH meter that has a female BNC probe input. Other types of connectors include DIN, threaded, T-type, and 3.5mm, etc. These types of connectors tend to be proprietary connectors for specific types of meters and are not interchangeable.

• Conventional electrodes are usually 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, or highly acidic or alkaline solutions, the positive flow of electrolyte through the junction often reverses, causing the sample solution to enter the reference chamber. If left unchecked, the reference electrode becomes contaminated, resulting in complete electrode failure. Another potential problem with single junction electrodes is junction clogging caused by silver chloride (AgCl) precipitation. In samples containing Tris buffer or heavy metals, silver readily precipitates. When the electrolyte solution contacts the sample, some AgCl precipitates on the outer surface of the junction. The result is drifting readings from the sensor.

• Hanna's double junction system, as the name implies, has two junctions, with only one junction in contact with the sample, as shown in Figure 0. Under adverse conditions, the same intrusion trend is also evident. However, when the reference electrode system is physically separated from the intermediate electrolyte region, contamination of the electrode is minimized. Double junction electrodes also reduce the likelihood of junction clogging because the outer reference cell uses a “silver-free” fill solution. Since no silver is present, no precipitate can form to clog the junction.