Perform your ion concentration measurements rapidly and accurately

Ion concentration measurement or ion-specific (ISE) measurements can be performed in every laboratory for a variety of sample types including water, food and beverage, pharmaceuticals, and biological samples.

To evaluate a sample's ion-specific performance, the best resource is slope S, also known from pH measurement. Whether you're looking to test ISE measurements through the direct method, dilution method, matrix match method, known addition method, or matrix factor method, our robust portfolio of ion-specific meters, electrodes, standards, and solutions are known for delivering accurate and reproducible ISE measurement results.

Choosing the best method for ISE measurement of your sample

The ion selective electrode (ISE) is a useful and versatile sensor for testing ions in various types of samples, such as environmental, agricultural, industrial, biotechnical, pharmaceutical, food, wastewater, drinking water, and others. Typical ions of interest include ammonia, fluoride, nitrate, chloride, calcium, sodium, potassium, silver, sulfide, iodide, bromide, lead, cadmium, copper, and others.

How does the sample type affect the ISE method that I use for testing?

  • Dilute aqueous (water) samples: Typical dilute aqueous (water) samples can be tested by simple, direct testing. Direct testing involves adding ionic strength adjuster (ISA) solution to standards and samples, calibrating with the standards, and testing the samples.

  • Complex or high ionic strength samples: Some sample types are not dilute aqueous solutions. Samples that are complex or have a high ionic strength background may require a different approach than the direct test method to obtain the best results. In general, high ionic strength samples are samples of >0.1M concentration of dissolved ions or samples that may have a conductivity reading of greater than about 10 mS/cm.

 

Examples of dilute aqueous samples  
  • Ultra-pure water
  • Potable water, ground water
  • Surface (natural) water
  • Treated wastewater, effluent
  • Cooling waters, boiler waters
  • Dilute solutions (e.g., < 1000 ppm)
 
Examples of complex or high ionic strength samples  
  • Seawater
  • Salt solutions, brines (e.g., >0.5%)
  • Many foods and beverages
  • Acid bath, alkaline solution (e.g, >0.3%)
  • Soil extracts (>0.1M extract solution) buffer solutions
 
To make an accurate measurement using an ISE, a suitable ISE method should be selected according to specific sample conditions.  
  • For complex or high ionic strength samples, addition of ISA may not be sufficient to normalize the ion's activity between the samples and the standards. In that case, choosing an alternate ISE method is recommended for accurate measurements.  
 
What if my sample is a solid or is non-aqueous (not water-based)?  
  • A solid sample must be prepared so that the ion of interest is dissolved or extracted into water. For example, a certain type of powder, salt, or tablet sample might be mixed with water to dissolve the ion of interest prior to ISE testing. A soil sample may be dried, crushed, and/or sieved, then extracted into a water or salt solution prior to ISE testing. The extracting solution is chosen to bring the ions of interest into solution, and the extracting solution must not interfere with the ISE test.
 
  • A non-aqueous liquid sample must be prepared so that the ion of interest is extracted into water. For example, an oil sample might be mixed with water or other extracting solution to extract the ion of interest into the water phase. The water phase is then tested. Alternately, the non-aqueous sample might be ashed or subjected to an oxygen combustion bomb preparation (e.g., EPA SW-846 Test Method 5050) to remove the organic matrix. After combustion, the inorganic residue is mixed with water and tested for ions. In some cases, the solid or viscous sample can be added directly to a standard solution and can be tested by analyte addition or subtraction.
 

Choosing the best method for ISE measurement of your sample

The ion selective electrode (ISE) is a useful and versatile sensor for testing ions in various types of samples, such as environmental, agricultural, industrial, biotechnical, pharmaceutical, food, wastewater, drinking water, and others. Typical ions of interest include ammonia, fluoride, nitrate, chloride, calcium, sodium, potassium, silver, sulfide, iodide, bromide, lead, cadmium, copper, and others.

How does the sample type affect the ISE method that I use for testing?

  • Dilute aqueous (water) samples: Typical dilute aqueous (water) samples can be tested by simple, direct testing. Direct testing involves adding ionic strength adjuster (ISA) solution to standards and samples, calibrating with the standards, and testing the samples.

  • Complex or high ionic strength samples: Some sample types are not dilute aqueous solutions. Samples that are complex or have a high ionic strength background may require a different approach than the direct test method to obtain the best results. In general, high ionic strength samples are samples of >0.1M concentration of dissolved ions or samples that may have a conductivity reading of greater than about 10 mS/cm.

 

Examples of dilute aqueous samples  
  • Ultra-pure water
  • Potable water, ground water
  • Surface (natural) water
  • Treated wastewater, effluent
  • Cooling waters, boiler waters
  • Dilute solutions (e.g., < 1000 ppm)
 
Examples of complex or high ionic strength samples  
  • Seawater
  • Salt solutions, brines (e.g., >0.5%)
  • Many foods and beverages
  • Acid bath, alkaline solution (e.g, >0.3%)
  • Soil extracts (>0.1M extract solution) buffer solutions
 
To make an accurate measurement using an ISE, a suitable ISE method should be selected according to specific sample conditions.  
  • For complex or high ionic strength samples, addition of ISA may not be sufficient to normalize the ion's activity between the samples and the standards. In that case, choosing an alternate ISE method is recommended for accurate measurements.  
 
What if my sample is a solid or is non-aqueous (not water-based)?  
  • A solid sample must be prepared so that the ion of interest is dissolved or extracted into water. For example, a certain type of powder, salt, or tablet sample might be mixed with water to dissolve the ion of interest prior to ISE testing. A soil sample may be dried, crushed, and/or sieved, then extracted into a water or salt solution prior to ISE testing. The extracting solution is chosen to bring the ions of interest into solution, and the extracting solution must not interfere with the ISE test.
 
  • A non-aqueous liquid sample must be prepared so that the ion of interest is extracted into water. For example, an oil sample might be mixed with water or other extracting solution to extract the ion of interest into the water phase. The water phase is then tested. Alternately, the non-aqueous sample might be ashed or subjected to an oxygen combustion bomb preparation (e.g., EPA SW-846 Test Method 5050) to remove the organic matrix. After combustion, the inorganic residue is mixed with water and tested for ions. In some cases, the solid or viscous sample can be added directly to a standard solution and can be tested by analyte addition or subtraction.
 

Thermo Scientific measurement products and solutions

Tackle your specific sample analysis challenges head-on with our rich portfolio of meters, electrodes, and solutions. High-quality meters are essential to the critical, routine tasks you perform every day. Our portfolio of benchtop and portable meters are designed to help you meet your sample analysis challenges across a wide array of industries and applications. We offer simple, complete systems that are seamlessly integrated to help address your measurement needs.

Our meters, electrodes, buffers, standards, and solutions are designed for a number of applications and industries:

 
  • General laboratory testing
  • R&D
  • Government compliance
  • Pharmaceutical
  • Power generation
  • Drinking water
  • Wastewater treatment
  • Food & beverage testing
  • Environment
  • General industrial processing
 

Ion Specific (ISE) 
Benchtop Meters

Ion specific benchtop meters

The accuracy and reliability of your ISE measurements depend on the instrumentation you use. Learn more about how you can identify the best match based on your required features, performance, specifications, and budget.

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Ion Specific (ISE) 
Portable Meters

Ion specific portable meters

Our portable meters are rugged and waterproof, and provide dependable performance in the field without sacrificing accuracy or reliability.


 

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Electrodes and Probes

Electrodes for Ion specific measurement

The accuracy and reliability of your measurements depend on the instrumentation you use. Learn more about how you can identify the best match based on your required features, performance, specifications, and budget.

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Buffers and Solutions

Electrodes for Ion specific measurement

We offer standards, electrode storage solutions, electrode cleaning solutions, and electrode filling solutions for your ISE measurement needs. Find the solutions that you need need for your process.
 

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Support

Knowledge Base: Certificates of Analysis and SDS for Orion, ROSS, AQUAfast, AquaMate, and AquaSensors products.

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