Accuracy, precision and reproducibility for pH measurement

For more than 40 years, ROSS pH electrodes have been helping to provide accuracy, stability and rapid response. Compared to conventional electrodes, the proven ROSS reference system exhibits stability in measurements, faster response, greater accuracy and precision when measuring samples that vary in temperature, or when calibrating in temperatures that differ from your samples.

ROSS pH electrodes are available in a variety of styles such as the clog free Sure-Flow junction, glass or epoxy electrodes, flat surface, semi-micro, micro, and spear tip designs. 

Select an electrodeDownload whitepaper

Kato Pharmaceuticals: Developing a Curative Treatment for Diabetic Retinopathy

Scientists at Kato Pharmaceuticals are developing a first-of-its-kind treatment for diabetic retinopathy and other ocular diseases using Thermo Scientific Orion VersaStar Pro Bench Meter and ROSS pH Electrodes.

  Increase your productivity by adding accessories to your benchtop or portable meter. Meter Accessories ›

ROSS Electrodes compatible with Orion Benchtop and Portable Meters*

ROSS pH electrode models

Extended life

Combined pH & temperature

TRIS compatible

Rugged bulb

Clog-free maintenance


Glass body

Ultra Triode Combination ›   
Ultra Triode Glass Combination ›   
Ultra Triode Low Maintenance Combination ›  
Ultra Triode Low Maintenance Combination, 3' cable ›  
Ultra Combination ›  
Ultra Glass Combination Semi-micro ›   
Ultra Flat Surface Combination ›    
Ultra Combination Semi-micro ›   
Reference Electrode ›     
Ultra Reference Electrode ›   
Sure-Flow Combination ›   
Sure-Flow Combination Semi-micro ›    
Rugged Bulb Combination ›   
Spear Tip Combination ›    
Half-Cell Combination ›    
Glass Combination ›    
Combination Semi-micro    
PerpHecT Combination Micro ›    
Combination ›     
Sodium Combination Ion Selective ›    
Sleeve Junction Combination ›     
Flat Surface Combination ›      

*Orion benchtop meters, including Versa Star, Orion Star, StarA. Review specifications for compatibility with the discontinued A-series meters or other brands. Screw cap electrodes require additional electrode adapter cable, screwcap to BNC, Cat. No. 91CBNC.

Explore application specific uses of ROSS pH and ion-specific electrodes 

Measuring pH of Pure Water and Other Low Conductivity Waters

ROSS Ultra triode pH-ATC electrode 

A low resistance junction works best when measuring pure water samples. Avoid a saturated silver electrode filling solution - a precipitate can form on contact with pure water, which may lead to clogging and high resistance in the junction. For this application, the Orion ROSS Ultra Triode combination pH-ATC electrode with capillary junction, which uses silver-free filling solution, is an ideal choice.

pharmaceutical pdf

Measuring pH of Water and Wastewater using the Thermo Scientific Orion Dual Star pH/ISE Meter

ROSS Ultra glass-body pH electrode


The use of pH in the treatment of wastewater requires quick, accurate and robust measurement. This application note describes how the Orion Dual Star pH/ISE meter paired with a ROSS Ultra glass-body pH electrode (Cat. No. 8102BNUWP) can help measure the pH levels in water and wastewater.

environmental pdf

Measuring pH in Surface Water

ROSS Ultra Triode pH-ATC electrode

The pH of surface water is a common field measurement. This measurement can be made using a ROSS Ultra Triode refillable combination pH-ATC electrode (Cat. No. 815BNUMD) which will measure both the temperature and pH of the sample with a single probe. The probe provides quick, reproducible results in both fresh and saltwater samples.

Water pdf

Determination of Sodium in Canned Vegetables by Automatic Multiple Known Addition Titration

ROSS ion selective electrode

Sodium in canned vegetables is determined using the Thermo Scientific Orion Star T930 Ion Selective Electrode Titrator preprogrammed method, Na Veg. The ROSS Sodium Combination Ion Selective Electrode (Cat. No. 8611BNWP) is used to sense the potential due to sodium concentration and determine the amount in the sample. 

Sodium pdf

Total Acid Number in petroleum products by automatic titration

ROSS sure-flow pH electrode

Total Acid Number (TAN) in a petroleum product is determined using the Orion Star T910 pH Titrator preprogrammed method T3 TAN. The ROSS Sure-Flow pH Electrode (Cat. No. 8172WP) is used to sense the alkalinity of the petroleum.

petrol pdf

What’s the secret to the precision and accuracy of ROSS electrodes? 

The distinctive orange coil, which is highly visible in the glass body version of the ROSS electrode, not only gives ROSS electrodes their distinctive look, but is a feature designed to increase electrode lifetime. 

The triodide/iodide system inside the coil provides a chemically stable house for the redox system and protects the electrode from contamination. The first ROSS electrodes were housed in a straight stem, but the product creators were not satisfied with the limitations of this design.

In addition to increasing the life of the electrode, designing a coil into the reference system provides the electrode with two technical advantages over a straight stem design. By significantly increasing the diffusion path to the reference wire, the coil minimizes changes near the reference wire caused by diffusion of fill solution through the reference junction to the inner electrolyte. The effective diffusion path is further increased by incorporating particles or polymers into the inner fill solution.

Find out more about ROSS technology by reading the whitepaper.

Download whitepaper


Learn more about the history of ROSS Electrodes

Since 1981, Thermo Scientific Orion ROSS Electrodes have been helping scientists achieve precise results in pH testing and measurements. The original ROSS pH electrode was the first of its kind to use a redox reference system. The redox system provides a stable reading within seconds and increased accuracy by at least 10 times compared to conventional electrodes.

The ROSS system has powered innovations and driven efficiency in ISE and pH testing by scientists and technicians across pharmaceutical, environmental, quality control, and academic labs for 40 years. We think that's something to celebrate and we hope you join us. 

Uncoiling the history of ROSS electrodes


The first “Ross” electrode was created in 1980 and introduced into the market in 1981 by Orion Research led then by it’s founders Dr. James Ross and John Riseman. The innovative pH electrode designed by Dr. Ross was based off of redox technology instead of relying on silver chloride, which can precipitate salts into the liquid junction. This system is 10 times more accurate compared to traditional methods and the drift rate is less than 0.002 pH per day. In 1984, Engineer and Glassblower Moshe Hirshberg would design the signature coil for which the ROSS electrode is known, to extend the lifetime of the product up to 2 years, and further cementing the legacy of Dr. Ross. 

pH and ORP
benchtop meters

find the right benchtop meter for your pH and ORP measurement needs

The accuracy and reliability of your pH and ORP 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.

pH and ORP
portable meters 

find the right portable meter for your pH and ORP measurement needs

Take your pH and ORP measurements to the field without sacrificing accuracy and reliability. Our portable meters are rugged and waterproof, and provide the dependable performance that your demanding applications require.

and probes

view our selection of electrodes

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.

and solutions

view our buffer and solutions

We offer buffers, electrode storage solutions, electrode cleaning solutions, lab buffer kits, and electrode filling solutions for your measurement needs. Find the buffers and solutions that you need for your process.


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

Orion Meters Software and Upgrades
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