HM Digital ORP-200 Waterproof Professional Series Handheld Meter, White/Green, ORP

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AOKI, K., NAKAO, A., ADACHI, T., MATSUI, Y. & MIYAKAWA, S. (2012). Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes. Medical Gas Research 2, 12. An ORP sensor consists of an measuring electrode, a reference electrode, and some sort of display, in much the same fashion as pH measurement. An ORP meter is really a millivolt meter, measuring the voltage across a circuit formed by the reference electrode and the measuring electrode. An ORP system does not have a high impedance source (like a pH bulb), but is a potentiometric device that produces a voltage. It also uses similar cables, connectors, and calibration solutions. For this reason, a high impedance electronic meter (pH) with many user-friendly features are a benefit for this measurement.

ORP readings are measured in mV and range from -2000 mV to 2000 mV. Values above zero indicate an oxidizing substance while values below zero indicate a reducing substance. Values do not indicate the concentration but rather the potential of the substance to oxidize or reduce. Kotz, John C., Paul M. Treichel, and John R. Townsend. Chemistry & chemical reactivity. Cengage Learning, 2011. pH stands for "potential of hydrogen" and is a measure of hydrogen ion concentration. A high concentration of hydrogen ions results in acidity while a low concentration results in alkalinity. The concentration of hydrogen ions is represented on a scale from 0 to 14 with 7 being neutral (i.e. an equal number of hydrogen (+) ions and hydroxide (-) ions to cancel each other out). Values below pH 7 are acidic and values above pH 7 are alkaline. The scale is logarithmic, meaning each full point increases or decreases by a factor of 10x. Some extreme substances can score lower than 0 or greater than 14, but most fall within the scale.Therefore, the answer to when to use ORP meters becomes a little complex. Although, a simplified answer to this question can be to use when the water is being treated or processed. The following are a few examples of applications where ORP meters can be used to identify water quality. OSTOJI?, S. M., STOJANOVI?, M. D., CALLEJA-GONZALEZ, J., OBRENOVI?, M. D., VELJOVI?, D., ME?EDOVI?, B., KANOSTREVAC, K., STOJANOVI?, M. & VUKOMANOVI?, B. (2011). Drinks with alkaline negative oxidative reduction potential improve exercise performance in physically active men and women: Double-blind, randomized, placebo-controlled, cross-over trial of efficacy and safety. Serbian journal of sports sciences 5, 83-89.

The electrode itself is comprised of a measuring electrode, a reference electrode, and, often, a temperature sensor. Electrode components are usually combined into one device called a combination pH electrode. The reference electrode is filled with an electrolyte of a known value which reacts with the medium being tested. That reaction is what determines the potential of hydrogen. Since pH is sensitive to temperature fluctuations, a temperature sensor is included so readings can be properly compensated. Temperature compensation can be achieved manually or automatically. Manual temperature compensation is usually achieved by entering the temperature of the fluid being measured into the instruments menu. Automatic temperature compensation requires input from a temperature sensor and constantly sends a compensated pH signal to the display. This is an important part to consider regarding the molecular hydrogen concentration. Because the pH plays such a large role in the ORP, you can have one glass of ionized water with an ORP of -800 mV and another with an ORP of -400 mV, but (because of pH differences) the second glass can actually have more therapeutic molecular hydrogen than the first glass. Remember, a negative ORP is more of an indicator of the presence of H 2gas than a measure of concentration. Indeed, it’s not a measurement of concentration at all. SHIRAHATA, S. A. N. E. T. A. K. A. (2002). Reduced water for prevention of diseases. Animal Cell Technology: Basic and Applied Aspects 12, 25-30. The redox probe is able to measure this electromotive force for electrons to pass from the reduced species to the oxidized species. In our vitamin C example, if the concentration of the oxidized and reduced forms of ascorbic acid are the same, then we will measure an ORP voltage of -570 mV. This is according to the standard redox half-reaction:

ORP

pH calibration on the meter is performed at either two or three points. You should calibrate with pH 7 buffer first then followed by either pH 4 and/or pH 10 buffers. The recommended frequency of calibration of pH is every 2 weeks. pH meters generally consist of a glass electrode connected to an electronic meter that measures and displays the pH reading. Meters can range from units that combine all the parts into a simple, handheld unit or more complex, laboratory-quality instruments that provide highly accurate readings and a host of other functions. Now that it discussed where and when one can use the ORP meters, then let us take forward to how ORP Meter works.