Even with proper care and maintenance, most pH electrodes usually last just 1-3 years. Storage beyond 3 years may be possible if sensor's response time, slope, and asymmetry potential are within the user's acceptable limits.

In this article, the goal is for you to learn the warning signs your pH meter is imploding and find out the 7 variables that will help you replace it with something that actually might last forever.

What is a pH meter and how does it work?

Well, first things first. A pH meter is a device you probably will first use, have used or been using for a really long time already but its purpose is basically to measure the changes in the activity of hydrogen ions in a solution, particularly its concentration levels. 

It is often used to measure acidity in soil, water, winery, also even in manufacturing, healthcare, and clinical applications that require pH chemistry. A basic understanding of pH level is that when you detect pH levels of less than 7, the solution is identified as acidic while those pH levels higher than 7 are alkaline. 

An acidic solution has far more positively charged hydrogen ions in it than an alkaline one, so it has greater potential to produce an electric current in a certain situation. Meaning, it’s like a battery that can produce voltage. Because of this, pH meter works like a voltmeter: 

It measures voltage (electrical potential) of an acidic solution and compares it to the voltage of another solution where the difference in its voltage (potential difference) between the two allows the determination of the difference in pH levels.

Your pH meter is able to measure because of its two parts: first, the meter itself which is like a moving-coil or digital meter, and your probes (electrodes) which have a silver-based electrical wire and are put in a solution to measure pH level through a phenomenon called ion-swapping process. This is where the hydrogen ions in a solution move toward the surface of the glass electrode and replace some metal ions. Some of the metal ions from the glass electrode move into the solution. The ions which attached to the surface of the glass electrode are what allow the determination of pH levels.

But don’t be too confused, all of those happened to measure pH levels: whether a solution is acidic or alkaline. Now let’s talk about how a pH meter is calibrated to get accurate results.

How to calibrate a pH meter?

Using a pH meter is pretty straightforward. There’s your solution to measure, your glass electrode to measure the pH level of your solution, and the measurement that you get. 

But calibrating a pH meter can be done in 4 steps.

Step 1, you clean the glass electrode with distilled water and a tissue to ensure that no particle from any acidic or alkaline solution from previous procedures is attached to the surface of the electrode and influence the measurements.

Step 2, you test the electrode by submerging it in two buffer solutions of different pH levels, usually in the range of 4 to 7, or 10. The pH meter should be able to read the assigned pH level of each of your buffer solution. Otherwise, you will need to edit the entry in your instrument to correct it. For each process, you will have to repeat step 1 before proceeding to test the electrode for another buffer solution.

Step 3, you will now be able to measure the pH of the substance or solution that you want to examine. If you are handling two or more solutions, always remember to rinse your electrode with distilled water before measuring for your next solution.

Calibrating your pH meter is important. Frequent calibration of your pH meter is recommended especially when it measures heavily contaminated, low-ion, strongly acidic, and high temperature solutions. Doing calibration ensures that your pH meter always get accurate results in measuring pH level of the solutions you are examining.

How to troubleshoot and reset your pH meter?

But there could be moments where despite calibration, your pH meter will not read the accurate pH measurement in your buffer or your actual solutions. There are 5 ways that you can troubleshoot your pH meter system is you encounter pH calibration problems:

First, check the age of your probes or electrodes. Commonly, probes last for 12 to 18 months, regardless if you frequently use them or not. If you’re probe has been operating beyond these timespan, that could explain why your system is not reading accurately. And it only means that you need to change it.

Second, check if the probe has never dried out. In storing your probe, it has to be placed in a moist environment or submerged in a buffer 4 solution. A dried out probe causes inaccurate reading, and could mean it needs to be replaced. Or if you stored your electrode using a different buffer solution or even a distilled water, the sensor in your electrode can be damaged which eventually affect your pH readings.

Third, resetting your calibration to Factory default if possible. While not all PH meter instruments is capable of default reset. Rest function varies depending on the model, so you can either refer to the your pH meter’s user manual or consult your manufacturer.

Finally, check if your electrode is not contaminated. If you have refillable electrodes, its electrolyte level should be at least 2 cm above the level of the measurement solution. Otherwise, it may have been contaminated and will need cleaning, worst, replacement.

If after all of these and your pH meter still doesn’t give you accurate readings, then there might be a bigger problem in your pH meter system that will need to be referred to an expert, to your manufacturer– to us.

How to maintain and take care of your pH electrodes?

And since your pH electrode is the most sensitive part for your pH meter system, it matters that you are careful in cleaning and storing it. It would be a hassle if your pH electrode dies out even if you just use it for a short time. That’s money we’re talking about that we could have saved!

So Just like your car, or your favorite shoes, your pH electrodes need a regular and routine care. Cleaning your pH electrode is usually done through flushing, refilling, and topping off your junction fluids. 

An important thing to remember in maintaining your electrode include your sensing bulb and reference junction to be immersed in a buffer solution at all times. It must not dry out, otherwise it may require reconditioning steps later on to bring back its functionality.

It is recommended to use pH 4 and 7 in calibrating pH electrodes, but for long terms storage (>1-week), a buffer 4 solution and should be placed in a storage bottle with protective cap. And while we’re talking about solutions, it also an important thing to select a quality buffer solution to make sure that your sensors operate well. Avoid using low-quality, home-made, or expired buffers. Using otherwise can cause measurement errors, which will require troubleshooting which can take up a lot of your time and energy.

You can also be mindful about the shelf life of your buffers. Most pH buffer solution except for pH 10.01 as per NIST standards, can only be used in a span of 2 years from the date of manufacturing. pH 10.1 buffer however can last for 18 months (1.6 years) from date of manufacture. pH 10.1 has a shorter shelf life as it is vulnerable to carbon dioxide contamination. 

Finally, once you pour a buffer in your electrode, it must immediately be disposed and shall not be poured back into your solution bottle. Doing so can guarantee that your pH electrode and your pH meter can last longer than other common pH meter system.

Thermo Scientific Orion pH Electrode Selection Guide

Guide to selecting your pH electrode

In selecting a more durable pH electrodes, there is no doubt that that outweighing the advantages and disadvantages of a product take a lot of your time and decision-making. To help you make up your mind, here are a few things that you may best consider in choosing your pH electrode.

1. Measurement Response and Stability
   
   Well, the greater accuracy in sample measurement, the less need for recalibration. And that makes the work done faster. So in choosing your pH electrodes, it is favorable to consider a system that has superior 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.
   
   
2. Temperature Response
   Difference in the temperature of your solutions can also affect your pH readings. That is why in choosing your electrodes, it is preferred if it can show immediate response and stable measurement even if temperature of your solutions range from cold 0 ºC or boiling 100 ºC. A good electrode can provide correct reading within a minute or less. Orion pH meters are capable of equillibrating your readings within 30 seconds compared to standard electrodes that is still not done within 3 minutes.
   
   
3. Resistance to Contamination
   The material where your electrode is made is a very crucial part to make careful considerations. Standard silver chloride electrodes has metals that is leach into solutions and can cause sample contamination, or clog into your electrode junction, make a sluggish response, and eventually inaccurate readings. It also reduce the life of your electrode. So, it’s important that you electrodes, like the Orion Ross electrode, not containing any silver or mercury or other metal material in it, so it be resistant to sample contamination.
   
   
4. Junction Design
   The junction is the reference electrode system which comes in contact with the sample. It usually can come as single or double junction design. Your single junction may be less expensive, however, under adverse conditions like high pressure, temperature, or highly acidic or akaline solution being sampled can enter into the reference compartment and can cause electrode failure. Double junction, on the other hand, although comes a bit pricy can be cost-effective. Even when due to adverse situation, the contamination can be avoided due to the fact that double junction electrodes isolate the reference electrode. In simple means, your junction potential influences the durability of your electrode. 
5. Chemical Compatibility
   In selecting your electrodes, you’ll want to check the compatibility between your sensor body and the chemicals that can be present in your samples. Common to electrodes are made up of polymer body, however, when your sample solutions have highly corrosive components, you may need to consider purchasing a glass body electrode. Glass body electrode is capable of resistance to reaction with chemicals that can degrade other substances (like polymers).
   
   Orion pH meters come with a glass or epoxy body-type which is extremely durable, can prevent breakage, and is compatible to handle solution with high temperatures.
   
   
6. Membrane Shape
   Your membrane is sensitive glass part of your electrode connected at the end of the electrode shaft. You often refer to it as body tip or body style. They come in variety of shapes depending on your application for pH measurements. It is important to note, however, the following:
   
   Bulb-shaped tips is use for general application and renders high accuracy;
   Rugged-shaped tips are for handling applications requiring sturdy or robust membrane;
   Flat-shaped tips are for surface measurements; and
   Spear-shaped tips are for penetrating soft solids.
   
   
7. Electrode Application
   Finally, whatever pH electrode design you’ll want depends what application you will be using it for. Some designs are beneficial for a specific application while some may not perform best when it cannot meet the demands of your application. But as your pH electrode makes the most crucial part of your pH meter system, you need to carefully decide whether you’re not your application will require rugged, corrosive, and solutions that are highly acidic or alkaline, including how frequent and massive will be your applications on a daily basis.
   
   It is important that in order to expect a better life expectancy for your pH meter system, it should require your minimal routine maintenance. If it happens that your system demand frequent recalibration or replacement of your pH sensors, then it may be best to consult your experts or manufacturer to advise you with the suited material for both your electrodes and pH meter system to perform your applications for you.
   
   

Daigger Orion pH Meter Series

But you don’t really have to look far or browse other webpages to look for what you are looking for. With Orion pH meters and Orion Ross pH electrode series, you get a wide-variety of models and pH meter system designs that are customizable to your needs. Benchtop system? Portable system? Handheld System? Refillable double junctions? Low maintenance electrodes? We got you covered!

THERMO SCIENTIFIC ORION STAR A121 PORTABLE PH METERS	THERMO SCIENTIFIC ORION STAR A221 PORTABLE PH METERS	THERMO SCIENTIFIC ORION STAR A211 BENCHTOP PH METERS	THERMO SCIENTIFIC ORION STAR A111 BENCHTOP PH METERS
THERMO SCIENTIFIC ORION STAR A111 BENCHTOP PH METERS	ORION VERSA STAR PRO ELECTROCHEMISTRY METERS	ORION DUAL STAR BENCHTOP METERS	ORION STAR A HANDHELD METERS

Your pH meter system don’t last forever but we can help you with how you can make the most of out its lifespan! Save money but maintain your efficiency!

All you need to do is book with us a consultation and we’ll get our best team to assist you with the needs of your system. With Orion pH meters, sky’s the limit for what you want in your system!