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 HI1612D uses low temperature (LT) glass, conical bulb, glass body, triple ceramic junction and is refillable with 3.5M KCl + AgCl.
Low Temperature Glass Formulation
The measurement of pH at very high temperatures is detrimental to the sensitive glass bulb and will shorten the life of it. A pH electrode with general purpose (GP) glass will have a resistance of 100 megaohms at 25℃ while the resistance of LT glass is around 50 megaohms at 25℃. As the temperature of the glass decreases in the sample, the resistance of the LT glass will approach that of GP glass. If using GP glass, the resistance would increase above the optimum range, resulting in increased impedance and ultimately affecting the measurement. The HI1612D is suitable to use with samples that measure from -5 to 70℃.
Conic Glass Tip
The conical shaped tip design allows for penetration into solids, semi solids, and emulsions for the direct measurement of pH in food products including meat, cheese, yogurt, and milk.
The glass body is ideal for laboratory use. The glass is resistant to many harsh chemicals and is easily cleaned. The glass body also allow for a fast transfer of heat to the internal reference electrolyte. The mV generated by the reference cell is temperature dependent. The faster the equilibrium the steadier the reference potential.
Triple Ceramic Junction
The triple ceramic junction allows a faster flow rate of electrolyte from the reference into the solution. A standard pH electrode will use a single ceramic junction that allows for 15 to 20 µL/hour of electrolyte to flow; the HI1612D has three ceramic junctions, providing for 40 to 50 µL/hour of electrolyte to flow. This high flow rate provides faster electrode response and more stable measurement in viscous solutions or samples of low conductivity, such as pure water, where a long stabilization time is often observed.
The HI1612D is a refillable probe. Since it is a double junction pH electrode the fill solution is the HI7071 3.5M KCl + AgCl. If using a refillable pH electrode, the fill cap should be removed prior to calibration and measurement. Removing the cap creates positive head pressure in the reference cell allowing for higher flow rate of electrolyte through the outer junction. A higher flow rate will result in a faster and more stable reading.
The HI1612D uses a DIN connector. This type of connector is generally proprietary to the meters they are supplied with and may not be interchangeable. The HI1612D is recommended for use with Hanna’s HI8314 pH meter. Other type of connectors include BNC, screw type, T-type, and 3.5mm to name a few.