↦ Using calibration buffer solutions to calibrate a pH meter

using ph buffer solutions

While beer making is a bit of a science, taking the ph level of your beer is like some kind of advance astrophysics lesson because it seems so complicated, what with all the calculations and formula.

Some guy called Nernst apparently had a lot to do with it.

Anyways, taking a pH reading can be complicated because a serious brewer needs to properly calibrate their pH meter so it gives a correct reading which then means the brewer can make a good call about how their beer is going.

And to calibrate your meter, you need calibration or buffer solution.

What is a buffer solution?

A calibration or buffer solution is a chemical solution that is used to calibrate a pH meter.

A buffer solution is one which resists changes in pH when small amounts acid or alkali are mixed with the buffer. Acidic buffer solutions are commonly made from a weak acid and one of its salts - often a sodium salt.

The buffer is used to develop a calibration curve. This a scientific method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration

In the case of calibrating a pH meter, at least three 'standards' are needed.

Without the standardized pH buffer to calibrate the meter, the results will not be accurate and thus give you the wrong impression.

pH meters tend 'drift away' from their calibrated settings, it's just their nature due to the product design. 

It thus very important to calibrate your pH meter often so that accuracy of your results is maintained.

Devices other than pH meters need calibration with a solution too, such as refractometers and conductivity meters.

What are standard buffer solutions?

The definition is that Standard pH calibration solutions should have an accuracy of +/- 0.01 pH at 25°C (77°F) and come usually in seven different pH values from 1.68 to 10.01.

The most popular and commonly used buffers are (4.01, 7.01, and 10.01). Good brands are dyed different colors so they can be easily identified by the brewer and thus used in the correct order.

Standard buffer solutions can be used to calibrate almost any common pH meter so you don't need to fall into the trap of say, for example, using a Hanna brand buffer for a Hanna meter. You could of course because Hanna make quality meters! 

This does mean that you can look at price and value per mls when deciding what brand to use.

There are two other kinds of calibration standards - Technical and Millesimal

Technical solutions come with a certificate of analysis (COA) which affirms that the solution will absolutely perform to the standard as described.

Millesimal calibration solutions are used in labs where an accuracy down to three decimal places is required, think along the lines of municipal drinking water plants, and medical research facilities where readings can be absolutely crucial to good human health outcomes!

Homebrewers generally just stick with standard calibration solutions which they often order online from Amazon.

Why you need to use fresh calibration solution

Brewers and testers should always use fresh calibration solution when calibrating one's pH electrode. 

All pH measurements are based on the pH calibration solution as a reference point so the solution needs to be pure and not contaminated. 

Think of this like contact lens solution, when it gets old, you don't use it to clean your lenses, you bin it and go with fresh.

It's generally recommended then that opened bottles of buffer solution should be dispensed with after they have been opened for 6 months. The higher the buffer's pH ( from  > 7 ), the quicker it will degrade.

If you are calibrating fairly infrequently, you may wish to consider using single-use solution sachets rather than bottled.

using buffer solution to calibrate ph meter

How do I use calibration solution?

Your meter's pH electrode should ideally be cleaned in purified water before placing it your pH calibration buffer. This reduces the chance of contaminating the solution

A good practice is to be to use two beakers/containers for each calibration buffer that you will use.

Your method would be to clean the pH electrode with purified water then rinse the probe in one of the beakers with the buffer then place the probe in the second beaker with buffer.

Repeat this practice for multiple calibration points.

For best results, the user must ensure the pH probe has been cleaned and that it is rinsed with clean water between calibration solutions to reduce contamination of the pH solutions.

Here's a handy video guide on how to use your meter with the buffer:

If your solutions are clear, make sure you mark them out before you begin calibrating! You could leave the bottle or sachet close to the beaker as a reference. 

To obtain a correct pH calibration reading, the unit's accuracy is very dependent on the accuracy and age of the calibration solutions used, and the condition and cleanliness of the pH probe tip. You will get a calibration error if the unit is not properly maintained as per the instruction manual.

Never reuse calibration solution

Once you have calibrated your device and then tested beer wort, you should dispose of the reference calibration solution.

Given it has been exposed to the environment and has had equipment placed in it, there's a fair risk of contamination - so adding that to your original sample can risk ruining all your fluid!

The same applies to reusing the test sample at a later date. Just don't chance it.

Check out these common ph testing mistakes for other ways to avoiding screwing up. 

Making homemade calibration solutions

While some brewers can try to make their own DIY solutions to save money, the results prove to be homemade buffers that are not accurate or stable. This is a wasted effort as the buffer can be guaranteed to interfere with the accuracy of the test results.

Thus, we don't recommend you try to make your own! Check out the options available on Amazon.

No comments:

Post a Comment