Iodine glass pH electrodes with temperature sensor.
The IoLine high performance pH electrodes use a patented three chamber system with an iodine reservoir in the iodine/iodide reference electrode. The reference system is a very important part of the high performance pH electrode. The standard hydrogen electrode has proven too difficult in practical use to gain more than a mere theoretical importance. The Ag/AgCl reference system, which is the most common reference system, can cause measuring instabilities originating from potential variations with changing temperature or reactions between silver ions and the measuring solution in the area of the diaphragm. IoLine high performance pH electrodes, in contrast, have the advantage of a much lower temperature sensitivity and a metal ion free reference system. The high performance pH electrode reference system is based on the following reaction:
I2 + I- + 2 e- <-> 3 I-
The ORP is thereby described by the Nernstian equation:
EH = Eo + RT/zF * ln ([I3-] / [I-]3)
Eo = 0.536 V, R = 8.314472 I/(K*mol), T in K, z = 2 und F = 96485.34 C/mol.
The stability of the reference system potential even at changing temperatures is the key to the IoLine high performance pH electrodes' superior response speed and measurement stability. Additionally, these high performance pH electrodes have a higher accuracy when compared to conventional Ag/AgCl pH electrodes.
A further advantage of the high performance pH electrodes is the fact that the component determining the potential, i.e. the Iodine, is continuously being resupplied from the patented three chamber reservoir system. The first high performance pH electrode chamber contains a supply which is used to refresh the reference electrolyte and the reference system of the second chamber with iodine in order to maintain the necessary I3-/I- concentration to create a stable reference potential. The electrolyte link between the second and the third chamber, which contains the exchangeable bridge electrolyte, is provided by the high performance pH electrode's internal diaphragm. The bridge electrolyte also provides the contact with the sample via the high performance pH electrode's diaphragm.
The high performance pH electrode's interior diaphragm is designed to allow only a minimal diffusion of I3-/I- (Tri-iodide/Iodide) into the bridge electrolyte. Hence, the iodine consumption in the high performance pH electrode's reference electrolyte is very low and needs only very little re-supplying from the first chamber. The supply is practically unlimited and guarantees a high stability of the potential and a long lifespan of the IoLine high performance pH electrodes. However the high performance pH electrodes are built with an integrated refill port in the electrode's head that enables easy refilling of the reference system. The high performance pH electrods have a built in temperature sensor to improve their performance even further over other pH electrodes.
Platinum diaphragm for fast response and high stability
Many of the high performance pH electrodes have a platinum diaphragm, developed by SI Analytics to increase the stability and response time of the iodine/iodide reference system. The platinum diaphragm allows for remarkably constant and reproducible measuring characteristics when using the IoLine high performance pH electrodes. It contains twisted platinum wires being fused into the glass shaft of the high performance pH electrode. The defined spaces of the platinum wires guarantee a continuous and steady electrolyte flow and high stability of the high performance pH electrode's reference system in all media and at changing temperatures.
The IoLine high performance pH electrodes have a reference system that is 100% free of metal ions. This means that the high performance pH electrodes will not contaminate the measuring media with metal ions allowing them to be used with Tris buffers. The high performance pH electrodes are particularly good in applications where rapid temperature changes may occur. For precision pH measurements in research and quality control i.e. chemistry, pharmacy, biotechnology, or food industry the high performance pH electrodes are an excellent choice.