Are Glass pH Electrodes Safe in Food Factories?

Everything you need to know about pH electrodes, plus a closer look at why glass electrodes are such a popular choice.

The accurate and reliable measurement of pH is essential to food safety, product quality, and process control. That is why pH meters – featuring highly-sensitive electrodes – are so widely relied upon across the food production industry.

In this article, we will address the most common questions surrounding pH electrodes, offering a closer look at how they work, the different design features, and the materials they are made out of.

We will also explore why Glass Electrodes are such a popular choice, with sites typically preferring to manage the risks of using equipment with a glass component.

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Help Guide: Caring for your pH meters & electrodes

How does a pH electrode work?

Typically, pH electrodes feature a glass membrane that separates a known reference solution from the test sample. Within the hydrated layer on the glass surface, the hydrogen ions in the sample engage in an ion exchange with the alkali ions.

This results in a potential difference between the inside and outside environments. The pH electrode creates a small electrical voltage that is based on this difference. The voltage is measured by the pH meter as a “millivolt signal” and inside the pH meter, the millivolt reading is converted into the familiar pH scale.

What are the most popular examples of electrode tips?

There are a variety of electrode tips available, used throughout the industry for a wide range of applications. Below are four of the most popular styles. They offer differing levels of durability and are suited to different types of samples – ranging from liquids and brines to meat and cheese.

Bulb Electrodes

Bulb Electrodes are the most common example of an electrode tip, suited to a wide range of food industry applications. They are favoured for their simplicity, reliability, and proven performance across laboratory and food factory settings. The curved surface of a Bulb Electrode provides a generous contact area, enabling highly accurate and stable measurements. As a result, this type of electrode is particularly well suited to the pH measurement of liquids and brines.

Flat-Surface Electrodes

Flat-Surface Electrodes are easy to clean and protect from fouling, something that is crucial if your team is taking pH measurements from sticky or residue-laden samples. This type of electrode is incredibly versatile, able to measure pH in both solid and liquids. Flat-Surface Electrodes have also been designed to measure pH directly on flat sample surfaces – providing uniform and reliable contact. Common examples include meat, cheese, and dough.

Knife Electrodes

Knife Electrodes feature a sharp, blade-like tip that has been engineered to penetrate solid or semi-solid food items such as meat, cheese, sushi-rice, and bread. This design feature enables direct pH measurement deep within the sample, without the need for extraction or liquification. Knife Electrodes have a stainless-steel sheath that ensures durability, reduces the risk of contamination, simplifies the cleaning process, and extends the lifespan of the electrode.

Spear-Point Electrodes

Spear-Point Electrodes will typically feature a slender, glass tip – ideal for piercing soft to semi-solid samples such as cheese, meat, dough, and fruit. Again, this reduces the need for extraction or liquification. In most cases, Spear-Point Electrodes will be reinforced with a food-safe plastic body, making them a suitable choice for the harsh demands of a food production environment. This can also make them easier to clean and less vulnerable to fouling. Spear-Point Electrodes are suited to a wide range of pH applications.

Electrode Bodies – What materials are they commonly made out of?

There are different options to explore when considering electrode bodies and the materials they are made out of. Below are four examples, alongside the pros and cons of each option.

For the sake of comparison, the table includes non-glass bodies. However, they are rarely used in the food production industry.

Material (Electrode Body)	Pros	Cons
Glass	High chemical resistance High heat tolerance High corrosion resistance Easy-to-clean	Fragile material Risk of broken glass
Epoxy Plastic	Highly durable and impact-resistant Easy-to-clean	Lower maximum temperature tolerance Not as chemically resistant as glass Risk of broken plastic
Stainless Steel	Highly durable and impact-resistant High heat tolerance High corrosion resistance Easy-to-clean	Typically more expensive
Non-glass electrodes	Eliminates concerns surrounding the risk of broken glass	Significantly more expensive Not designed with the food production industry in mind

Glass Electrodes and risk management

Accurate, reliable, and resistant to high temperatures, Glass Electrodes are a popular choice throughout the food production industry. If you decide to introduce an electrode with glass components to your site, it’s important that you manage the risks effectively. The eight steps listed below will help you to do this:

Risk Assessments

No matter which style of electrode you select, it is standard practice to carry out a risk assessment before any new equipment or instrumentation is introduced to your site.

Ongoing Training

Ongoing training will play an important role in ensuring your team are treating their pH electrodes with care and are only using them for suitable applications.

Safe Storage

To reduce the risk of electrode damage, you will need to keep them wet in Electrode Storage Solution and clean off any residue using Electrode Cleaning Solution.

Instrument Stations

Introducing Instrument Stations for your pH meters will reduce the risk of the electrodes being cracked or chipped between use, as they will have a dedicated home.

Avoid Undue Damage #1

Electrodes should never be stored in deionised water, samples, solvents, hydrofluoric acid, or pH buffer solutions containing mercury-based preservatives.

Avoid Undue Damage #2

It’s important that the glass bulb / flat tip of the electrode doesn’t come into contact with oily or abrasive objects – bare fingertips are a common example.

Equipment Inspections

The glass membrane of your electrodes should be regularly inspected for cracks and chips. Ideally, a quick yet thorough inspection should take place before and after every use.

Breakage Protocols

There needs to be a documented protocol in place should any breakages occur. It will need to outline the correct procedure for containment, disposal, and batch review.

That brings us to the end of our guide to choosing the right pH electrodes for your site. If you have any questions about the options available, you can contact us directly on 01473461800 or sales@klipspringer.com. Alternatively, you can fill out the contact form below.

You can learn more about the Klipspringer range of pH electrodes via our Online Portal. You can also take a look at our dedicated Help Guide, covering the best way to care for your pH equipment.