Which variables have an affect on an Oxidation Reduction Potential (ORP) measurement?

Document ID

Document ID TE9830

Published Date

Published Date 27/03/2019
Question
Which variables have an affect on an Oxidation Reduction Potential (ORP) measurement?
Summary
Factors influencing ORP measurements
Answer
Oxidation Reduction Potential (ORP) is not an ion specific measurement, but a "sum parameter" as it is affected by all ionic activity and expresses the relationship between all of the oxidants and reductants in the sample matrix being analyzed.  If the ORP reading is to be correlated to chlorine concentration (or any other oxidant/reducer) in the sample, the variations in temperature, pH, ionic strength, as well as each ion's relationship to the ORP measurement would have to be known and accounted for (controlled), or completely eliminated as variables.  The ORP reading alone cannot accurately represent the concentration of chlorine (or any other oxidant/reducer) because these variables all have direct influence on the ORP measurement.