Storing pH buffer solution

[Huff360]

I have recently picked up a pH meter and the associated buffer solutions. The buffers are marked "Store at room temp" but we live in an older house in the south with a very inefficient A/C unit. It is not unusual for my 'room temp' to be 80-82 on hot days.

Would my buffer sachets be better stored in the fridge with the kegs at mid 40s or stored in the brew closet swinging with the house temp?

 

[AZBrewing]

I use pH meters frequently with buffers and live in AZ. My meters see temp above 80 often and are fine. The recommended temp is 50F-77F if you want to be by the book. Also, there is an expiration date to use by but if you are a bit over you will be okay. Just watch your slope on the meter when you do your calibration. The 7pH buffer is the most important calibration if doing single point but a better bet is to do a 3 point (4,7,10). Happy brewing

 

[ajdelange]

All (or almost all) chemical reactions are slowed by lowering temperature so putting buffers in the fridge would make for a longer shelf life but I too would recommend being guided by the expiration dates. If you do decide to refrigerate the buffers warm them up to the same temperature as the sample before using. ATC or no the best results are obtained if the buffers and samples are at the same temperature as it then does not matter how close to 7 the isoelectric pH of the meter falls (should be 7). Four and 7 buffer are stable in air (pthalate and phosphate respectively) but 10 buffer isn't (carbonate)but then you don't need 10 buffer for 99% of brewing applications. You will not get a better reading at brewing pH by doing a 3 point calibration. Four and 7 suffice and the good news is that the best accuracy is achieved half way between the pH's of the calibrating buffers that span the pH of concern. (4 + 7)/2 = 5.5 - right near where we usually measure pH. By contrast single point calibration results in measurements that are only accurate near the pH of the buffer being used. Since mash pH's are half way between 4 and 7 the results will be approximately equally disastrous whichever you use.

 

[Huff360]

Thanks guys. I appreciate the input.

I picked up the 4 and 7 buffers and plan on doing two point calibrations and keeping an eye on the expiration dates. We also have a fish tank and plan to use the meter there are well. We will probably need to use it at least twice a month so the expiration shouldn't be an issue.

I am planning to keep a log book of the calibration parameters as well.

 

[ajdelange]

I am planning to keep a log book of the calibration parameters as well.

This is a smart thing to do. It allows you to monitor the aging of your electrode. You might want to have a look at the Sticky in this topic (Brewing Science) on pH meter calibration if you haven't already done so.

 

[Huff360]

This is a smart thing to do. It allows you to monitor the aging of your electrode. You might want to have a look at the Sticky in this topic (Brewing Science) on pH meter calibration if you haven't already done so.

Well dern - I thought I was going to keep a logbook, but it turns out my meter (Hanna HI98129) doesn't give me any of the calibration info. It looks like I am out of luck.

 

[AZBrewing]

Well dern - I thought I was going to keep a logbook, but it turns out my meter (Hanna HI98129) doesn't give me any of the calibration info. It looks like I am out of luck.

No worries, your meter should give you an "ok" if your Cal was accepted. Keep your electrode in solution also or you will be replacing your electrodes often.

 

[diS]

I have question about saving calibration suspension:
I calibrated my pH meter few days ago (it was my last buffer solution) and I decide to keep suspended solution in 250 ml bottle.
Can it be used for future calibrations?
If yes, at what temperature should I keep it?

 

[ajdelange]

Ideally you should used freshly prepared buffers for each calibration or, if you have purchased the buffers in large stock bottles, you should withdraw a few mL for each calibration and discard what you have used after you have done the calibration. The concern is contamination of the buffers with sample or the other buffer in the pair or the DI water used to rinse buffers and samples from the electrode.

If you have to use buffer solutions which have previously been used because they are all you have then store them at room temperature in tightly sealed bottles.