You will find there are a lot of different models of pH meter ranging from simple pen devices to high end bench top meters and not to mention the large choice of electrodes to choose from. Here’s an overview of what you need to know about pH:
What is pH?
pH meters measure the degree of acidity or basicity of a solution which is proportional to the amount of Hydrogen ions there are in a solution. A reading on the pH scale between 0-14 will tell you that values above 7 exhibit basic properties, 7 is neutral, and below is acidic. The scale was established by Danish biochemist, Sorensen, who expressed pH mathematically as pH = -log [H+].
How is pH measured?
The most common way to accurately measure the pH of a solution is to use a pH electrode and a pH meter. A pH meter measures the voltage difference between the reference and measuring cells in a electrode and converts it to a reading on the pH scale.
pH electrodes or combination pH electrodes are used for measuring the pH of solutions, they have a combined reference and measuring cell in a single body. These are often made of glass or plastic/epoxy and come in a range of sizes, sensitivities and junction types for different samples. For testing the pH of brewing solution a standard combination electrode will do fine. Be aware that the pH meter you go for will only fit a certain electrode connector; BNC, S7, DIN ect, this is something to keep in mind when choosing your electrode.
Expect an electrode to need replacement after 1-2 years, they are very sensitive and can be damaged easily. To prolong their life make sure you keep the sensor in electrode storage solution when not in use and read our blog about cleaning & reviving electrodes.
For testing the pH of brewing solutions it is important to look for a high accuracy meter that can measure ideally to the nearest 0.01 pH. If you are going to be moving about in the lab taking samples as you go, a portable pH meter may suit you. A suitable high spec portable meter is the FiveGo F2 which has a resolution of 0.01 pH, accuracy of 0.01 pH and can be calibrated to 3 points. Buying a temperature probe with this meter would be advised.
If you are looking for something that can sit on your bench with a large screen and robust structure, you may want to look at our range of benchtop meters. For example, the FiveEasy F20 has an easy to read display, +/-0.01 error limits, 3 point calibration and memory to store your readings to USB. Any electrode with a BNC connector can be used with this unit.
Before measurements are taken the electrode or measuring sensor should be calibrated with pH buffers. pH buffers are liquids which have a set and constant pH. They can be bought as ready to use liquids in bottles or as single use sachets, or in powder form which must be made up with deionised water in a volumetric flask.
Exposing the electrode to pH buffers is effectively like showing the electrode what pH 4 “looks like”, or what pH 7 “looks like”. It will then use this as a reference point later when measuring pH unknown samples. We recommend calibrating your meter at the start of each day or before each testing session. Picking a meter that has a three point calibration against buffers 4, 7 & 10 is recommended.
Temperature at calibration
An important point to take into account is the temperature you calibrate your pH meter at – we have buffers that are made for use at room temperature 20 and 25°C. For an accurate reading you need to make sure that the sample you are measuring the pH of is at the same 20 or 25°C temperature at which you calibrated.
We understand that sometimes there is no time to wait for your boiling hot sample to cool on the side – . a nifty solution to this problem is to freeze your glass containers, adding your hot sample to bring the temperature down in minutes.
Click the links to find out about measuring the bitterness or colour of your beer. If you have any questions about testing pH in brewing please give our technical team a call on 01954 233 120, email us firstname.lastname@example.org or fill in the below form.