• HI1332P is a PEI body, double junction pH electrode with a BNC and pin connector. The pin connector is used to enable the CAL Check function of the HI2221, HI2222, and HI2223 benchtop meters. The electrode has a single ceramic junction in the outer reference cell, and the pH sensing portion is made of general purpose glass and is protected by an extension of the durable PEI body. This design consideration is ideal for field applications and general purpose use.

• Durable PEI body

• Double junction design

• Refillable electrode

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

• The HI1332P uses general purpose (GP) glass, spherical bulb, polyetherimide (PEI) body, single ceramic frit, and double junction.

General Purpose Glass Formulation

Measuring pH at very high temperatures is detrimental to the sensitive glass bulb and will shorten its life. A pH electrode with general purpose (GP) glass will have a resistance of 100 megohms at 25°C, while LT glass has a resistance of about 50 megohms at 25°C. As the glass temperature decreases in a sample, the resistance of LT glass will approach that of GP glass. If GP glass is used, the resistance will increase above the optimum range, resulting in increased impedance and ultimately affecting the measurement. The HI1332P is suitable for samples from 0 to 70°C.

Spherical Bulb

The spherical bulb is general purpose. Other tip shapes include conical for penetration and flat tip for surface measurements.

PEI Body

The HI1332P body is composed of polyetherimide (PEI) resin. The PEI body is suitable for a wide range of applications and excels in field measurements due to its durability. The shielding around the spherical glass tip minimizes breakage due to accidental bumping or dropping of the electrode. PEI plastic is a high quality plastic that is chemically resistant to many aggressive chemicals.

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, which houses the Ag/AgCl reference wire; the electrolyte outside this compartment is silver free. The double junction design means that virtually no silver enters the sample from the electrode. This design allows for measurement in applications where silver ions in the sample are undesirable or where silver precipitates may form on the junction.

BNC+Pin Connector

• The HI1332P uses a BNC+Pin connector. The BNC type connector is universal in that it can be used on any pH meter that has a female BNC probe input. The pin connector is used to enable the CAL Check function on the following benchtop pH meters; HI122, HI123, HI221, HI222, HI223, HI2221, HI2222, and HI2223.

• Conventional electrodes are normally single junction. As shown in the figure above, these electrodes have only a single junction between the internal reference wire and the external solution. Under adverse conditions, such as high pressure, high temperature, high acidity or alkalinity solutions, the positive flow of electrolyte through the junction is often reversed, resulting in the sample solution entering the reference chamber. If left unchecked, the reference electrode may become contaminated, resulting in complete failure of the electrode. Another potential problem with single junction electrodes is junction clogging due to silver chloride (AgCl) precipitation. Silver easily precipitates in samples containing Tris buffer or heavy metals. When the electrolyte solution contacts the sample, some silver chloride will precipitate on the outer surface of the junction. The result is a drifting reading obtained from the sensor.

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