Electrodes

pH Electrodes for the laboratory

We offer pH electrodes or combination electrodes for pH measuring devices from Mettler Toledo, WTW and SI Analytics. The electrodes can be used in a wide range of applications such as pH measurements in food testing. The chemical composition, homogeneity, temperature, process pressure and the pH range of the sample are important criteria when choosing the right electrode. Contact our customer service to assist you on selecting the right electrode.

A pH electrode selection guide can be found here.

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Product Image of Cable, 5 m, S7/S8, BNC
Cable, 5 m, S7/S8, BNC
Item number: PRQA824X
Brand: Dissolution Accessories
€65.36
Product Image of Cable, 2 m, S7/S8, BNC
Cable, 2 m, S7/S8, BNC
Item number: PRQA822X
Brand: Dissolution Accessories
€58.59
Product Image of Cable, 1 m, S7/S8, BNC
Cable, 1 m, S7/S8, BNC
Item number: PRQA820X
Brand: Dissolution Accessories
€52.40
Product Image of Metal-Combination Electrode (ATEX II 1/2G), Type AgS 8281 HD
Metal-Combination Electrode (ATEX II 1/2G), Type AgS 8281 HD
Item number: SI285118836
Brand: SI Analytics
€388.00
Product Image of Metal-Combination Electrode, Type AgS 6181 HD
Metal-Combination Electrode, Type AgS 6181 HD
Item number: SI285118811
Brand: SI Analytics
€369.00
Product Image of pH-combination electrode Typ 405DXKS8/225, Model name : PL 80-225pH
pH-combination electrode Typ 405DXKS8/225, Model name : PL 80-225pH
Item number: WW109234
Brand: WTW
€354.00
Product Image of SenTix® 51 combined pH-electrode
SenTix® 51 combined pH-electrode
Item number: WW103651
Brand: WTW
€268.00
Product Image of Electrode RedCap pH 405-60-T-S7/120/9848
Electrode RedCap pH 405-60-T-S7/120/9848
Item number: MR59904591
Brand: Mettler-Toledo
€392.00
Product Image of ELECTRODE PH U402-M3-S7/200
ELECTRODE PH U402-M3-S7/200
Item number: MR59904572
Brand: Mettler-Toledo
€600.00
Product Image of ELECTRODE PH LOT402-611-DPA-S7/40
ELECTRODE PH LOT402-611-DPA-S7/40
Item number: MR59902917
Brand: Mettler-Toledo
€403.00
Product Image of ELECTRODE U-402-S7/120
ELECTRODE U-402-S7/120
Item number: MR59902854
Brand: Mettler-Toledo
€303.00
Product Image of ELECTRODE InLab 413 IP67
ELECTRODE InLab 413 IP67
Item number: MR52000379
Brand: Mettler-Toledo
€323.00
Product Image of pH combination electrode Pb2+
pH combination electrode Pb2+
Item number: MR51344730
Brand: Mettler-Toledo
€1,445.00
Product Image of pH combination electrode NO3-
pH combination electrode NO3-
Item number: MR51344727
Brand: Mettler-Toledo
€1,445.00
Product Image of pH combination electrode Na+
pH combination electrode Na+
Item number: MR51344724
Brand: Mettler-Toledo
€665.00
Product Image of pH combination electrode K+
pH combination electrode K+
Item number: MR51344721
Brand: Mettler-Toledo
€1,445.00
Product Image of pH combination electrode I-
pH combination electrode I-
Item number: MR51344718
Brand: Mettler-Toledo
€1,315.00
Product Image of pH combination electrode F-
pH combination electrode F-
Item number: MR51344715
Brand: Mettler-Toledo
€1,315.00
Product Image of pH combination electrode Cu2+
pH combination electrode Cu2+
Item number: MR51344712
Brand: Mettler-Toledo
€1,445.00
Product Image of pH combination electrode CN-
pH combination electrode CN-
Item number: MR51344709
Brand: Mettler-Toledo
€1,315.00
Product Image of pH combination electrode C1-
pH combination electrode C1-
Item number: MR51344706
Brand: Mettler-Toledo
€1,315.00
Product Image of pH combination electrode Ca2+
pH combination electrode Ca2+
Item number: MR51344703
Brand: Mettler-Toledo
€1,445.00
Product Image of pH combination electrode Ag+/S2-
pH combination electrode Ag+/S2-
Item number: MR51344700
Brand: Mettler-Toledo
€1,445.00
Product Image of Electrode pH half-cells InLab Mono Pro
Electrode pH half-cells InLab Mono Pro
Item number: MR51343196
Brand: Mettler-Toledo
€304.00
Product Image of Electrode pH half-cells InLab Mono, replaces MR51343197
Electrode pH half-cells InLab Mono, replaces MR51343197
Item number: MR51343195
Brand: Mettler-Toledo
€161.00
Product Image of Electrode InLab Reference Flow
Electrode InLab Reference Flow
Item number: MR51343192
Brand: Mettler-Toledo
€327.00
Product Image of Electrode InLab Reference
Electrode InLab Reference
Item number: MR51343190
Brand: Mettler-Toledo
€160.00
Product Image of pH combination electrode InLab Hydrofluoric
pH combination electrode InLab Hydrofluoric
Item number: MR51343176
Brand: Mettler-Toledo
€380.00
Product Image of pH combination electrode InLab Cool
pH combination electrode InLab Cool
Item number: MR51343174
Brand: Mettler-Toledo
€348.00
Product Image of pH combination electrode InLab Semi-Micro
pH combination electrode InLab Semi-Micro
Item number: MR51343165
Brand: Mettler-Toledo
€328.00
Product Image of InLab Flex-Micro, pH electrode InLab
InLab Flex-Micro, pH electrode InLab
Item number: MR51343164
Brand: Mettler-Toledo
€484.00
Product Image of pH combination electrode InLab Semi-Micro-L
pH combination electrode InLab Semi-Micro-L
Item number: MR51343161
Brand: Mettler-Toledo
€364.00
Product Image of pH combination electrode InLab Surface
pH combination electrode InLab Surface
Item number: MR51343157
Brand: Mettler-Toledo
€309.00
Product Image of pH-Elektrode InLab Solids Pro IP67
pH-Elektrode InLab Solids Pro IP67
Item number: MR51343156
Brand: Mettler-Toledo
€490.00
Product Image of pH combination electrode InLab Solids
pH combination electrode InLab Solids
Item number: MR51343153
Brand: Mettler-Toledo
€366.00
Product Image of InLab Viscous Pro, pH electrode InLab
InLab Viscous Pro, pH electrode InLab
Item number: MR51343151
Brand: Mettler-Toledo
€670.00
Product Image of pH combination electrode InLab Viscous
pH combination electrode InLab Viscous
Item number: MR51343150
Brand: Mettler-Toledo
€499.00
Product Image of pH combination electrode InLab Power
pH combination electrode InLab Power
Item number: MR51343110
Brand: Mettler-Toledo
€477.00
Product Image of pH combination electrode InLab Routine Expert Pt1000, replaces MR51343015
pH combination electrode InLab Routine Expert Pt1000, replaces MR51343015
Item number: MR51343105
Brand: Mettler-Toledo
€286.00
Product Image of pH combination electrode InLab Routine Expert NTC30
pH combination electrode InLab Routine Expert NTC30
Item number: MR51343104
Brand: Mettler-Toledo
€286.00
Product Image of pH combination electrode InLab Routine Expert DIN, replaces MR52000497
pH combination electrode InLab Routine Expert DIN, replaces MR52000497
Item number: MR51343103
Brand: Mettler-Toledo
€296.00
Product Image of Electrode pH InLab Expert 2m
Electrode pH InLab Expert 2m
Item number: MR51343102
Brand: Mettler-Toledo
€388.00
Product Image of pH combination electrode InLab Routine Expert Pro
pH combination electrode InLab Routine Expert Pro
Item number: MR51343101
Brand: Mettler-Toledo
€328.00
Product Image of pH combination electrode InLab Routine Expert
pH combination electrode InLab Routine Expert
Item number: MR51343100
Brand: Mettler-Toledo
€204.00
Product Image of pH combination electrode InLab Reach Pt1000
pH combination electrode InLab Reach Pt1000
Item number: MR51343062
Brand: Mettler-Toledo
€411.00
Product Image of pH combination electrode InLab Reach Pro
pH combination electrode InLab Reach Pro
Item number: MR51343061
Brand: Mettler-Toledo
€411.00
Product Image of pH combination electrode InLab Easy BNC
pH combination electrode InLab Easy BNC
Item number: MR51343011
Brand: Mettler-Toledo
€169.00
Product Image of pH combination electrode InLab Easy
pH combination electrode InLab Easy
Item number: MR51343010
Brand: Mettler-Toledo
€125.40 €132.00
Product Image of LE410-DIN, pH electrode, incl. fixed cable with DIN plug for compatibility with other instruments
LE410-DIN, pH electrode, incl. fixed cable with DIN plug for compatibility with other instruments
Item number: MR51340348
Brand: Mettler-Toledo
€220.00
Product Image of LE427 pH insertion electrode ideal for solid samples
LE427 pH insertion electrode ideal for solid samples
Item number: MR51340333
Brand: Mettler-Toledo
€231.00

What is required for pH measurements?

A special measuring tool for hydronium ions which the pH value refers to, is required to measure the pH value. The principle of the measurement is based on a sensor with a glass membrane, which selectively detects hydronium ions and registers the reaction between the membrane and a sample solution. This glass electrode potential alone does not provide sufficient information, a second sensor is thus required which provides the reference potential for the pH sensor. To determine the pH value of the solution, the potential difference between these electrodes must be measured.

The reaction of the pH-sensitive glass electrode depends on the concentration of the H+ ions (or H3O+). Hence, pH is a measurement of both acidity and alkalinity, a selective measurement of hydronium ion activity. On the other hand, the reference electrode does not react to the concentration of the H+ ions in the sample solution and always delivers the same constant potential which is used to measure the potential of the pH sensor. The difference in potential between the two electrodes determines the pH of the solution. Since this potential is a linear function of the hydronium ion concentration in the solution, the concentration can be measured quantitatively.

Nowadays, the pH sensor and the reference sensor are very often housed in one electrode. This combination of reference and pH electrode is called a combined pH electrode. Each of these three types of electrodes is different and has its own characteristics and properties.

pH Electrodes

The pH electrode is the component that actually registers the pH of the solution. It consists of a glass shaft with a thin glass membrane at the lower end that is H+ ion sensitive. When this membrane comes into contact with an aqueous solution, the outside of the membrane glass forms a gel layer. A similar gel layer is also formed on the inside of the membrane glass as the electrode is filled with an internal aqueous electrolyte solution.

The H+ ions in and around the gel layer can - depending on the pH value and thus the H+ ion concentration of the measurement solution - either diffuse into or out of the layer. If the solution is alkaline, the H+ ions diffuse out of the layer and a negative charge is created on the outside of the membrane. Since the glass electrode has an internal buffer with a constant pH value, the potential on the inner surface of the membrane remains constant during the measurement. The potential of the pH electrode is therefore the difference between the inner and the outer charge of the membrane.

Reference electrodes

The task of the reference electrode is to provide a defined stable reference potential against which the potential of the pH sensor can be measured. To achieve this, the reference electrode must be made of glass, which is not sensitive to the H+ ions in the solution. It must also be open to the sample environment in which it is immersed. An opening or a diaphragm is made in the shaft of the reference electrode through which the inner solution or the reference electrolyte can flow into the sample. To obtain correct measurements, the reference electrode and the pH half-cell must be in the same solution.

The electrode construction consists of an inner reference element that is immersed in a defined reference buffer solution and has indirect contact with the sample solution via the diaphragm. This contact chain ensures a stable potential. There are several reference systems available, but the silver/silver chloride system is now used almost exclusively in laboratories. The potential of this reference system is defined by the reference electrolyte and the silver/silver chloride reference element. It is important for the reference electrolyte to have a high ion concentration and a low electrical resistance.

As the reference electrolyte flows into the sample during the measurement, pay attention to possible reactions between the reference electrolyte and the sample solution. Such reactions could affect the electrode and measurement.

Combined electrodes

Combined electrodes are much easier to handle than two separate electrodes and are therefore used very frequently today. In the combined electrode, the pH-sensitive glass electrode is surrounded concentrically by the reference electrode, which is filled with the reference electrolyte. The pH and reference components of the combined electrode have the same properties as the corresponding separate electrodes. The only difference is that they are integrated in a single electrode for easier handling. The use of individual pH and reference electrodes instead of a single combined electrode is only recommended if the two components of the combined electrode have a very different expected life span.

To further simplify pH measurements, a temperature sensor can be used together with the pH and the reference element in the same shaft. This enables temperature compensation while measurung pH. Such electrodes are also referred to as 3-in-1 electrodes.

pH and redox electrodes for every application

Electrodes may consist of different materials (very common are platinum, calomel or hydrogene electrodes) and are hence very versatile. They are knowned as single-rod measuring cells which are used to determine the pH value. However, the standard hydrogene electrode serves here as the reference electrode to determine the standard potential of redox couples. The most common ones are solid state electrodes containing of a metal and its dilution. Liquid electrodes such as quicksilver electrodes can also be used. 

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