pH solutions and endpoints

pH solutions and endpoints

Post by Ben Rott » Wed, 09 Jan 2002 20:19:30



Hi all,
A couple of questions on pH solutions and endpoints:

Firstly, I was originally thinking of getting pH 4.01 and 7.01 buffer
solutions for my pH meter (as recommended by the manufacturer) but
Ive read that a third calibration point at 10.01 increases
accuracy around the TA endpoint and one at 3.01 increases accuracy
when measuring wine pH (which makes perfect sense of course). Anyone
recommend getting these extra (10.01 & 3.01) buffers, or is it not
worth it? Is it worth getting a deionized rinsing solution too?

Secondly, I know that pH 8.2 is a convention for the TA endpoint (a
convention ?because? phenolphthalein changes colour at this point) but
Ive heard of some winemakers using an endpoint convention of pH
7. European/American differences? Something else?

Thanks,
Ben

 
 
 

pH solutions and endpoints

Post by Greg Coo » Wed, 09 Jan 2002 22:43:21


On 1/8/02 5:19 AM, in article

Quote:

> Hi all,
> A couple of questions on pH solutions and endpoints:

> Firstly, I was originally thinking of getting pH 4.01 and 7.01 buffer
> solutions for my pH meter (as recommended by the manufacturer) but
> I’ve read that a third calibration point at 10.01 increases
> accuracy around the TA endpoint and one at 3.01 increases accuracy
> when measuring wine pH (which makes perfect sense of course). Anyone
> recommend getting these extra (10.01 & 3.01) buffers, or is it not
> worth it? Is it worth getting a deionized rinsing solution too?

I only use 7 and 4.  If you are using your pH meter to do titration up to
8.2, I would probably calibrate it with the 10 as well.

Yes, use deionized water - it is important to keep your electrodes working
properly.  You can purchase distilled water in the supermarket for not much
money.

Quote:

> Secondly, I know that pH 8.2 is a convention for the TA endpoint (a
> convention ?because? phenolphthalein changes colour at this point) but
> I’ve heard of some winemakers using an endpoint convention of pH
> 7. European/American differences? Something else?

The endpoint you want is the higher one.

----Greg

http://www.ndsu.nodak.edu/instruct/grcook/wine/