How to choose a pH electrode for lab use vs. hobby use
Thermo Scientific’s best pH electrodes. For every application.
Orion, the god of hunting in Greek mythology. He was one of the greatest warriors of all time. So great that Orion, with his club, shield and sword at the ready, has been immortalized in the sky with one of the most recognizable constellations.
Much like Orion, Thermo Scientific's Orion Combination pH electrodes are ready for battle.
And just like Orion, these pH electrodes are legendary.
The best Orion Thermo Scientific pH electrodes
For the general purpose lab.
- General purpose lab work
- Ideal for dirty or viscous samples
What’s great about it:
- Versatile 3-in-1 electrode, available in 4 styles
- Durable epoxy body
- A safe choice, as the:first electrodes to meet all RoHS standards, containing no hazardous components.
- Easy disposal, because it’s lead-free and mercury-free
- Free flowing, liquid-to-liquid junction that resists clogging (just press the cap to flush the junction area)
For the scientist or hobbyist on a budget.
- Clean-water measuring
- Great for laboratory and field applications that require occasional disposal and frequent testing
What’s great about it:
- Sturdy epoxy-coated, single-junction electrode
- Economy electrode, with a pH range of 0 to 14
- Low-maintenance, gel-filled model and replaceable model
- A safe choice, meeting all requirements of RoHS standards, containing no hazardous components. It’s the first laboratory electrode containing a glass bulb that conforms with RoHS regulations (other glass bulb pH electrodes are constructed with glass that contain about 20% lead)
- No disposal costs or issues, because it’s lead-free and mercury-free
- Equipped with waterproof BNC connector that’s compatible with any pH meter with a BNC input
A premium option for aqueous samples.
- Quickly & efficiently measuring free ions in aqueous states
- Can be used with smaller sample volumes
What’s great about it:
- Stable, drift-free premium option
- Solid-state sensing membrane and epoxy body, with waterproof BNC connection
- Easy to use, if junction clogs, just flush it by pressing the cap
- Comprehensive, with no additional reference electrode necessary
- Fluoride electrode meets requirements for ASTM D 1179: fluoride in drinking water
- Built to last, and comes with a 12 month warranty
An all-in-one solution.
- Conducting precise pH determinations for samples varying in temperature
What’s great about it:
- Virtually drift-free, with optimum stability, even in samples varying in temperature
- Compatible with Tris buffers
- Built to last, with an unmatched two year warranty on all six styles
- Added features. Comes with all the benefits of a traditional ROSS electrode, with the added benefit of a built-in temperature sensor.
- All in one, measuring pH, mV and temperature, all in one electrode
- The right fit for you, available in both refillable and gel versions. Comes in glass or epoxy bodies: ceramic, glass fiber or sure-flow junctions
- Versatility: Measures pH range from 0 - 14 and temperature range between 0°C–100°C
- Low maintenance: Less drift over time means less calibrating
- New technology: Unique internal reference system developed by Orion offers greater accuracy, reproducibility, stability and faster response times than any other standard electrode line.
Remember to pair your new pH electrode with the right pH meter. This is one of the most popular options.
Choosing the right pH electrode.
Not all pH electrodes are created equal.
And, as with any measuring device, finding the right tool for your specific task is essential. Without careful selection, it’s easy to miss out on features that could have made your life (A LOT!) easier, or pay for features that aren’t going to help you at all.
Whether you’re testing samples in the lab, in quality control, the food and beverage industry or health care, one incorrect measurement can have drastic (and devastating consequences.
Why take chances with a low quality electrode?
For over 35 years, chemists, other scientists and serious hobbyists have relied on Thermo Scientific’s Orion pH electrodes. Orion tools are known worldwide, and synonymous with precision and durability.
Your other electrodes may come and go. They may be difficult to calibrate, clean or maintain. They may leave you questioning precision and accuracy. Or maybe they just don’t last long.
Orion pH electrodes are some of the most stable, responsive and precise tools around, for when you need...
- To ensure safety, and have confidence in the validity of your pH measurements
- Highly reproducible pH measurements to comply with strict GLP or GMP operating procedures
- The critical control point pH measurements to keep up with your manufacturing process
- Rapid and reproducible pH measurements in the field, at any temperature, to keep up with your workload
- A low-maintenance tool that doesn’t require frequent calibration and lasts a long time and doesn’t break your budget
- To run multiple tests but have a limited amount of sample, and need to retain sample integrity
What are pH electrodes used for?
Lots of industries already rely on a pH electrode for everyday use.
Whether you’re testing samples in pharma, food, or general lab work, it’s essential that you measure your samples quickly and precisely, and that your day-to-day measurements are accurate and reproducible.
Common applications of Orion pH electrodes include…
- Consumer health products: Product safety is of the utmost importance, and you need to be confident in the validity of your pH measurements.
- Pharmaceuticals: You need highly reproducible pH measurements to comply with strict standards (and GLP & GMP operating procedures)
- Food & Beverage Quality Control: Critical control point (CCP) pH measurements have to keep up with your manufacturing process.
- Field Water Testing: Rapid and reproducible pH at any temperature needs to be efficient for field testing to keep up with workload and keep EPA compliant.
- Quality Control: You need a reliable, long-lasting electrode that doesn’t require regular maintenance or calibration,especially when budgets are tight and throughput is critical.
- Contract Testing Laboratory Work: You need to run multiple tests, but have a limited amount of samples to work with and need to retain the integrity of your samples.
What’s the best pH electrode for my application?
The Thermo Scientific Orion electrode line offers a wide variety of quality pH electrodes to choose from. There are many different factors to consider when you selecting a pH electrode to ensure you select the electrode that will suit your needs. You will need to consider body materials, body styles, and sample requirements.
For example in the food industry, safely canning food products involves maintaining a careful pH balance, which is especially essential for acidic foods that are close to the canned food pH limit of 4.6. Digital pH meters are widely used in the industry. However, water treatment facilities might require advanced pH electrodes to support multi-functional purposes, and be equipped with an adaptable pH sensor to measure dissolved oxygen, conductivity, redox potential, specific ions and salinity.
Here’s our guide to help you choose the correct pH electrode.
|Industry & sample type||Electrode recommendation|
|Biological & pharmaceutical industries (TRIS buffer, proteins, enzymes)||A ROSS electrode like the Orion Ross Ultra pH Electrode or double junction Ag/AgCl reference (no sample contact with silver)|
|Education & student use||An epoxy body for added durability for regular use and new users. The Orion Low-Maintenance pH Electrodes is a great option for frequent (and sometimes rough) use.|
|Emulsion (food, cosmetics & oils)||The Orion Sure-Flow Combination Electrode or open junction to prevent the electrode from clogging|
|Emulsion (petroleum products & paints)||A glass body that resists damage from the sample, and an Orion Sure-Flow Combination Electrode or open junction to prevent clogging|
|Flat surfaces (cheese, meat, agar)||A flat-surface tip and Orion Ross Ultra pH Electrode or double junction Ag/AgCl reference (no sample contact with silver)|
|Flat surfaces (paper)||A flat surface tip|
|General purpose (most sample type)||The standard Thermo Scientific Orion Combination pH Electrode is a great option for general use, without added cost of features you won’t need|
|Harsh environments (field or plant use, rugged use)||An epoxy body for added durability and polymer or gel filled for easy maintenance, like the Orion Low-Maintenance pH Electrodes, designed for frequent use and field work.|
|High ionic strength (acids, bases, brines, pH >12 or pH <2).||A Orion Sure-Flow Combination Electrode or open junction for better contact with the sample and more stable measurements.|
|High temperatures||A ROSS reference like the Orion Ross Ultra pH Electrode for longer life and/or a quick flow junction for fast response|
|Larger sample size (tall flasks)||Look for a long body that fits your container|
|Low ionic strength (treated effluent, deionized water, distilled water)||Refillable for better contact with the sample and more stable measurements|
|Nonaqueous (solvents, alcohols)||A glass electrode that resists damage from the sample and an Orion Sure-Flow Combination Electrode junction for better contact with the sample and more stable measurements|
|Semi-solids - fruit, meat, cheese||A spear tip for piercing samples and an Orion Ross Ultra pH Electrode or double junction Ag/AgCl reference|
|Small sample size - microtiter plates||Look for a small diameter that fits your container|
|Small sample size – NMR tubes||Look for a small diameter that fits your container|
|Small sample size – test tubes, small flasks and beakers||Look for a small diameter that fits your container|
|Small sample size – TRIS buffer, proteins, sulfides||A small diameter that fits the container and an Orion Ross Ultra pH Electrode or double junction Ag/AgCl reference|
|Titration||A Orion Sure-Flow Combination Electrode or sleeve junction for better contact with the sample and more stable measurements|
|Viscous liquids - slurries, suspended solids sludges||A Orion Sure-Flow Combination Electrode or open junction to prevent the electrode from clogging|
|Waters – acid rain, boiler feed water, distilled water, rain water, well water||A ROSS like the Orion Ross Ultra pH Electrode or double junction Ag/AgCl reference that is refillable for better contact with the sample|
|Waters – drinking water, tap water||An epoxy body for added durability. The Orion Low-Maintenance pH Electrodes is great for clean-water measuring and built for regular use.|
|Waters – wastewater, seawater||A ROSS like the Orion Ross Ultra pH Electrode or double junction Ag/AgCl reference and have an epoxy body for added durability|
Still not sure what the right choice is?
Back to basics: What is pH?
pH is one of the most common laboratory measurements, because so many processes are dependent on the pH value. The term comes from the combination of “p” (for power) and “H” (the atomic symbol of hydrogen).
pH is an easy way to compare the relative acidity or alkalinity of a solution at a given temperature.
A pH scale measures the acidity or alkalinity of a substance, on a scale from 1 to 14.
- A pH above 7 indicates the solution is basic (or alkaline), because the activity of hydroxide is greater than that of the hydrogen ion
- A pH of 7 indicates a neutral solution, because the activities of the hydrogen and hydroxide ions are equal
- A pH below 7 is acidic, because the activity of the hydrogen ion is greater than the hydroxide ion
A note on pH and temperature
The most common reason for error in pH measurement is temperature. Temperature variations can influence the pH because:
- The electrode slope will change with variations of temperature
- Buffer and sample pH values will change with temperature
- Measurement drift can occur when the internal elements of the pH and reference electrodes are reaching thermal equilibrium after temperature change
- Measurement drift can occur when the pH electrode and temperature probe are placed in a sample that does not have uniform temperature
To mitigate this chance for error, some electrode models, like the Thermo Scientific Orion Ross Ultra pH Electrode come with the additional benefit of a built-in temperature sensor.
How do pH electrodes work?
There’s a big range in the pH electrodes available.
- Some are designed for one specific task. Others are more versatile.
- Some take direct measurements with the use of a probe. Others use a chemical analysis called titration.
- You might need precision measurements. You may not. You may need specialized features for your task. Or perhaps something durable and general purpose will do just fine.
pH electrodes are analytical sensors that measure the potential of hydrogen (pH), the negative logarithm of the hydrogen ion activity in a sample or solution. The pH measure of a sample is directly related to the ratio of the hydrogen ion [H+] and the hydroxyl ion [OH-] concentrations.
So many chemical processes are dependent on pH, which is why so many industries turn to trusty pH electrodes.
A pH electrode works by producing an electrical potential between two liquids of different pH when they come into contact with opposite sides of a thin glass membrane (the pH element). The pH element is permeable by hydrogen ions, and the pH electrode is filled with a neutral solution (containing an equal amount of H+ and OH- ions).
- When the pH probe is immersed in the H+ solution, the glass membrane is permeated by the H+ ions, exerting a positive potential on the sensing electrode. This potential difference is measured by a pH meter.
- When the pH probe is immersed in an alkaline (basic) solution, the H+ ions move outside of the probe, leaving an excess of OH- ions within the probe, and a negative potential is sensed by the pH meter.
Who’s using pH electrodes?
The list is long. There are thousands of different tasks, jobs and circumstances that need to measure pH regularly. Just a few examples include:
- Pool and spa facilities: Measure the water’s pH to determine how much chlorine needs to be added to the water to ensure it’s a safe swimming environment for all of us.
- Research labs: Water is an essential ‘ingredient’ in many experiments, and scientists need to monitor pH levels in research to ensure high-quality findings that are replicable.
- Aquariums and fish tanks: It’s important to monitor water composition (including pH levels) to make sure fish can thrive. Fun fact - fish do best at pH levels between 6.5 - 9.0!
- Wineries: For routine analysis of their stock, wineries use pH monitors.
- Wastewater management: Facilities measure and offset pH levels while removing toxic substances from water, to make sure they end up with a safe, clean final product.
- Food and beverage: pH is measured across the industry to make sure products are safe to consume and high quality when they get to us.
- Aquaculture: This multibillion-dollar industry is responsible for supplying nearly half the world’s seafood! Measuring pH levels regularly ensure aquatic creatures are healthy enough to be consumed.
Electrode types, features and compatibility vary, and are important to consider when choosing your pH electrode. They’re available with a glass body or an epoxy body, and in a variety of electrode body styles, junctions, fill types, references and connectors to suit your specific needs. We’ll explore choosing the right one in this article. And the accuracy of your pH measurements depend on the instrument you use, which is why it’s so important to make a smart choice you can depend on.