During the development of our voltammetry reference electrodes our goal was to achieve the best possible performance from each of the materials used so we considered several different frit materials such as sintered ceramic, Vycor glass, ground-joint, sleeve junction and Pt thread. Each of these techniques vary in structure and in performance, however Vycor glass and sintered ceramics are generally the most accepted.
Vycor is a type of porous glass with pore sizes of around 4 nm and gives a modest leaky rate with quite low impedance (500 Ω). A major drawback for Vycor glass however is that it cannot be used in alkaline solutions as the frit will simply disintegrate.
In précis, Ionode has chosen sintered ceramic as the frit material as it features a wide working temperature range of 0-100 °C, relatively low impedance, excellent alkaline resistance, a low leaky rate which is less likely to contaminate samples with chloride ions and offers pore sizes that can be fine-tuned to suit your applications.