representing Pfaudler pH/ORP Electrodes

See Pfaudler's New Glass/Steel pH/ ORP Technology.......

An Exciting New Technology for Difficult pH/ ORP Measurements!  

The new Pfaudler Model 18/ 40 pH electrodes change the nature of pH measurements by eliminating the porous low impedance KCl reference electrode. The new structure also eliminates all internal solutions for both the measuring and reference electrodes. It uses a pH glass for the measuring electrode, a high impedance sodium ion glass for the reference electrode and includes an internal RTD for temperature compensation. It also incorporates a rhodium solution ground that can also be used for high-resolution pH compensated ORP measurements. The electrode can be used with transmitters that have dual high impedance amplifiers manufactured by several leading suppliers.

Understanding Pfaudler pH/ ORP Theory

Electrode construction starts with an inert glass coated steel rod. The pH glass, sodium ion glass and rhodium solution ground are fused on the enamel coated inert carrier.  The smooth high gloss ceramic type surface also inhibits formation of scale and coating.  The dual high impedance glass on both the measuring and reference electrodes minimize electrochemical interference from coating and fouling. This unique construction permits the rugged robust pH/ ORP probe to be useful in pulp and paper, chemical, pharmaceutical/ biotech, brewing, heat exchange applications that may include, high temperature, low temperature, oily emulsions, organic solvents, precipitations and difficult waste treatment processes.

The absence of an internal solution on the measuring electrode also prevents slope (span) drift. The probe can be sterilized at 130 Degrees Celsius as often as required without degradation or drift. A key feature to remember is the probe is actually rejuvenated by the steam sterilization cycle. Eliminating the internal solutions permit the probe to also be used in very low temperature heat exchange applications that may include organic solvents.  Since the probe uses the background salt in the process water for the reference voltage, it can be "Grab-Sample" calibrated. The Pfaudler 18/ 40 probes are defined as a process calibrated electrodes; not buffer calibrated as are traditional pH electrodes.

The benefits of the new technology are the ability to be: left dry without any degradation or need to recalibrate, used with high viscosity materials, not easily fouled by process solids (up to 14% pulp stock), not poisoned by organic solvents in the process solution, operate at a wide range of temperature and pressure, and requires minimal calibration or maintenance. The result is a process pH probe that does not Drift! 

For more information see "Applications" section  

Understanding pH  Compensated (High-Resolution) ORP

Conventional ORP applications use a noble metal electrode to sense the ratio of oxidized/ reduced reagent in a process. They all use a conventional KCl reference electrode with a porous junction. This junction is subject to all the same problems coating, fouling, poisoning, etc as covered under pH theory above. The measurement chemistry is also sensitive to errors caused by any change in the pH of the process solution. We have an equation with two variables and one unknown. In essence the ORP can change due to the reaction of the process reagent and/ or the pH. This situation severely limits the effectiveness of conventional ORP measurements.

What is pH compensated ORP? It uses a noble metal for the measuring electrode (Rhodium) but eliminates the porous KCl reference electrode. It replaces the conventional reference electrode with a pH glass electrode. Since the voltage of the pH glass changes with any change in pH of the solution the ORP voltage becomes unaffected by the process pH. The resulting ORP voltage is just the reagent voltage with no interference from pH variation. The pH compensated ORP measurement eliminates the affects of process pH changes on the ORP value. This high-resolution reading permits more accurate chemical dosing and better product quality.

Typical applications where high-resolution ORP is needed can be found in paper processes such as bleaching, de-inking, removing bleach, sterilization of pulp, etc. In pharmaceutical/ biotech processes reaction end points, product degradation, etc. Waste treatment can require pH compensated ORP to insure all hazardous wastes have been removed prior to discharge. Cooling towers can use it to more accurately dose expensive biocide control.

Where does the Pfaudler Technology solve real pH/ ORP problems?

Independent tests by customers have shown the probe to have better stability, be faster responding and more reproducible than conventional probes. Typical applications where the probe out performs arespecialty chemicals, pharmaceuticals, nutriceuticals, biotech, catalytic processes, sterols,  headbox, stuff box, hardwood stock, bleaching, washing, cooking liquors, scrubbers, starch cooking, acidulation, emulsions, organic resins, cheese whey dehydration  multi-phase water/ organic mixes, SIP (steam-in-place) sterilization, CIP (clean-in-place), caustic and acid boil outs, brewing, oily wastes and difficult bio-wastes.  See the various pH/ ORP electrode mountings under "Pfaudler Electrodes".  

Reiner... Pressurized Flowing Reference Electrode

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Last modified: February 19, 2008