Since I got my pH meter I've never entirely trusted the calibration buffers I've been using. So I decided to buy some others and do a comparison to see the level of consistency between them.
I bought some ready made Hanna buffers from here: http://www.servovendi.com/uk/ph-buffer- ... 7004m.html (actually I bought via ebay, but the same price). They're somewhat pricey, but given that I only use 10ml at a time I should be able to get 20+ calibrations out of a pair of bottles of pH 7.01 and 4.01. The Hanna bottles came sealed with a use by date of December 2021.
The second option I have are some unbranded packets of a dried crystalline buffer that I bought from ebay. £9.95 delivered for 10 sets. They have to be mixed with 250ml of deionised water before use - but I have no idea how long they last for once made up (to be investigated later): http://www.ebay.co.uk/itm/PH-Buffer-Sol ... 1987636293
Finally, the capsules I bought with my pH meter. They are made by Greisinger, and you simply add deionised water to the capsule contents. Once mixed they need 24 hours before use, and are good for 3 months according to the instructions. https://www.rapidonline.com/greisinger- ... x1-60-3789
The solutions I have was made up three weeks before testing.
pH meter calibration buffer comparison
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Jocky
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pH meter calibration buffer comparison
Ingredients: Water, Barley, Hops, Yeast, Seaweed, Blood, Sweat, The swim bladder of a sturgeon, My enemies tears, Scenes of mild peril, An otter's handbag and Riboflavin.
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Jocky
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Re: pH meter calibration buffer comparison
Here's the various buffers. The coloured ones are the greisinger solutions.
Between pH tests I use the wash bottle to clean the pH probe with deionised water before patting dry with kitchen towel.
Ingredients: Water, Barley, Hops, Yeast, Seaweed, Blood, Sweat, The swim bladder of a sturgeon, My enemies tears, Scenes of mild peril, An otter's handbag and Riboflavin.
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Jocky
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Re: pH meter calibration buffer comparison
I'd got all of the solutions to the same temperature in advance to avoid pH variation due to temperature - all the solutions were at 17.5 C
So first of all I calibrated the pH meter with the Hanna solutions. At 17.5c the pH 7.01 solution would read as 7.03 and the 4.01 solution as 4.00. After putting the pH probe in the solution it was left for 5 minutes to stabilise.
The second set of solutions I then tested were the unbranded packets from ebay. At 17.5c the pH 6.86 buffer should measure 6.89, and actually read 6.87. The pH 4.00 buffer should read 4.00, and actually read 4.01. Both of those are much closer to the Hanna solutions than I expected they would be.
Finally, the Greisinger capsule solutions should read 7.02 and 3.99 at 17.5c . They actually read 6.93 and 4.10.
There's nothing scientific about what I've done, it was just a rough comparison of the various pH buffers I'd acquired, and thought it might be of interest.
So first of all I calibrated the pH meter with the Hanna solutions. At 17.5c the pH 7.01 solution would read as 7.03 and the 4.01 solution as 4.00. After putting the pH probe in the solution it was left for 5 minutes to stabilise.
The second set of solutions I then tested were the unbranded packets from ebay. At 17.5c the pH 6.86 buffer should measure 6.89, and actually read 6.87. The pH 4.00 buffer should read 4.00, and actually read 4.01. Both of those are much closer to the Hanna solutions than I expected they would be.
Finally, the Greisinger capsule solutions should read 7.02 and 3.99 at 17.5c . They actually read 6.93 and 4.10.
There's nothing scientific about what I've done, it was just a rough comparison of the various pH buffers I'd acquired, and thought it might be of interest.
Ingredients: Water, Barley, Hops, Yeast, Seaweed, Blood, Sweat, The swim bladder of a sturgeon, My enemies tears, Scenes of mild peril, An otter's handbag and Riboflavin.
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BenB
Re: pH meter calibration buffer comparison
Nice work Jocky. Really sweet little experiment. At the very least suggests that one source of calibration solutions is okay. 