pH meters - how often to calibrate?

[portveyn]

How often do you calibrate your pH meters?
How often do you use them?

 

[BobF]

I cal every time I use it, which is every few weeks. I usually wait until I have several batches to test before I get it out.

 

[whackfol]

Every day I use it.

 

[Runningwolf]

I would calibrate at least every two weeks if your continuously using it. Otherwise each time you use it. Also as your electrode gets old, you may find out you'll need to calibrate more often.

 

[ibglowin]

Each time you turn it on or daily.

 

[portveyn]

It's seems pretty expensive to calibrate an pH meter for each little batch.
Makes sense to wait and check all at ones as BobF said.

Thanks, everyone!

 

[ibglowin]

You don't have to pitch the Buffer solution once you use it. It can be used over and over pretty much. Just make sure your rinsing your electrode well with DI water between readings. My pH meter came with a handy 2 oz plastic obtainer with a screw lid. I poor two ounces in and reuse it for 6 months or so.

 

[Flem]

Question for the chemist (Mike). Since you re-use your buffer solutions, does rinsing the electrode with distilled water and then putting the used buffer solutions back for re-use affect the solutions by being slightly diluted over time with the distilled water? Granted it would be a very small amount of residual distilled water left on the probe after each use.

Mike

 

[ibglowin]

The whole thing about buffers is their ability to resist a change in pH due to small additions of strong acid or base. Distilled water will not effect it much since its not a strong acid or a strong base it can take a lot and not change the pH. That said, I always rinse well with distilled water between samples etc, then use a soft tissue and blot the probe on the tip and other areas that I can see that are wet so by the time I get ready to sample again or recalibrate the pH meter the probe is completely dry or almost. Water doesn't hang around long in my neck of the woods (5% relative humidity this time of year). I usually toss and get new buffer about every 6 months or if you see any off buffer reading (like wayoff).

 

[BobF]

The whole thing about buffers is their ability to resist a change in pH due to small additions of strong acid or base. Distilled water will not effect it much since its not a strong acid or a strong base it can take a lot and not change the pH. That said, I always rinse well with distilled water between samples etc, then use a soft tissue and blot the probe on the tip and other areas that I can see that are wet so by the time I get ready to sample again or recalibrate the pH meter the probe is completely dry or almost. Water doesn't hang around long in my neck of the woods (5% relative humidity this time of year). I usually toss and get new buffer about every 6 months or if you see any off buffer reading (like wayoff).

Kinda like diluting your red wine sample with distilled water so you can see the color change when doing an acid test!

Good info Mike!

 

[Runningwolf]

Ditto what Mike said. I do the same at home and work.

 

[Flem]

The whole thing about buffers is their ability to resist a change in pH due to small additions of strong acid or base. Distilled water will not effect it much since its not a strong acid or a strong base it can take a lot and not change the pH. That said, I always rinse well with distilled water between samples etc, then use a soft tissue and blot the probe on the tip and other areas that I can see that are wet so by the time I get ready to sample again or recalibrate the pH meter the probe is completely dry or almost. Water doesn't hang around long in my neck of the woods (5% relative humidity this time of year). I usually toss and get new buffer about every 6 months or if you see any off buffer reading (like wayoff).

Thanks for the feedback, Mike!

 

[portveyn]

How different readings could be if the 'bulb' is not cleaned well but calibrated? Is it +/- 0.1 pH or could it be really dramatic for simple home winemaker?

 

[ibglowin]

It could be dramatic as in +/- a full pH unit. You can't really calibrate a dirty probe. It tends to just keep drifting and never fully stabilize.