Because pH and conductivity are common measurements used for an extensive range of applications, a common question put to the Instrument Choice Scientists is "What is the Relationship Between pH and Electrical Conductivity?".
Unfortunately, explanations involving pH and conductivity can take up entire chapters of textbooks, and often become overly complex. We put together this article in response to requests for a simplified explanation – without the scientific jargon.
What is pH?
The potential of hydrogen or 'pH' is the measure of hydrogen ion concentration in a sample used to determine the acidity or alkalinity of a product. The pH scale ranges from 0-14 with 0 being acidic, 7 being neutral, and 14 being alkaline.
What is Electrical Conductivity (EC)?
Electrical conductivity is the measure of the concentration of ions present within a sample. The calculation of conductivity involves the ability of a substance to transmit an electrical current over a defined area. The measurement unit for electrical conductivity is called Siemens(S). You will most commonly see conductivity expressed in MilliSiemens per centimetre (mS/cm) or MicroSiemens per cm (μS/cm).
OK, What is the Relationship Between pH and Electrical Conductivity?
As discussed, pH is the measurement of a specific ion (i.e., hydrogen). On the other hand, electrical conductivity is a non-specific measurement of the concentration of both positively and negatively charged ions within a sample. So the short answer to the question about the relationship between pH and conductivity is as follows, the presence of any hydrogen ions present in a substance will impact the pH level and most probably influence conductivity levels. However, hydrogen ions make up only a small part of the ion concentration measured by a conductivity meter. The relevance of the relationship will depend on the presence of hydrogen in comparison to other concentrations of non-pH determining ions.
pH and Electrical Conductivity Meter Examples
Given the relationship between pH and conductivity, it's not surprising that for some applications, you may need to measure both parameters. Instrument manufacturers have recognized this need and responded with an extensive range of meters that combine the measurement of pH and conductivity for enhanced usability. Check out two of the most popular product examples below or browse the full range of pH and conductivity meters here.
Waterproof Multi-Purpose Meter
Product Code: EC-PCSTestr35
The EC-PCSTestr35 is an accurate, easy-to-use, and highly popular multiparameter tester. This meter boasts an all-in-one replaceable sensor for a wide range of practical purposes, such as measuring the five key parameters in swimming pools, aquariums, hydroponic operations, cooling towers, food processing plants, and more.
Specifications
pH Range: 0.00 to 14.00
pH Accuracy: 0.01 pH
Conductivity Range: Two ranges 1 uS / 0.01 mS and 0 uS/cm to 20.00 mS/cm
Conductivity Accuracy: ±1 % full scale
Also measures: Salinity, TDS and Temperature
PC60 Premium Multiparameter Pocket Tester Kit
Product Code: IC-PC60
Forget the need for multiple meters. The IC-PC60 simultaneously tests pH/EC/TDS/Salinity and Temperature in a quick, accurate, and reliable manner. A portable carrying case accommodates a complete kit, which includes the meter itself, starter calibration solutions, calibration bottles, storage solutions, AAA batteries, and a lanyard!
Specifications
pH Range: -2.00 to 16.00 pH
pH Accuracy: ±0.01 pH ±1 digit
Conductivity Range: 0 to 200.0 μS, 0 to 2000 μS and 0 to 20.00 mS/cm
Conductivity Accuracy: ±1 % full scale
Also measures: Salinity, TDS and Temperature
Conclusion
Although the relationship between pH and conductivity can be a moving target, there is overlap in that pH indicates the concentration of hydrogen ions, and the measurement of conductivity determines the total number of ions present in a sample.
Want more information on pH and conductivity meters? Not sure which meter will best suit your needs? Speak with an Instrument Choice Scientist! We're here to help! Call 1300 737 871 or email customer-service@instrumentchoice.com.au.