Use caution when testing TA with ph meter

[sour_grapes]

At times I've wondered, if before electricity, if A/O might of still existed, but instead of an electric pump, like a bunch of guys blew into a little hose. When one was out of breath, the next guy tapped the shoulder of the guy waiting to blow next, then he took over, using a manifold of course.

I can just see these guys now, complaining about, how this little electric pump was going to put them all out of business.

Then along came the pH meter.

Edit: I use both, am I crazy or what? I'm waiting... @sour_grapes.

Totally not sure why you called me out, but here is the first thing that came to my mind about your amusing "manual" A/O scenario: What if one of the human bellows had lots of garlic with lunch? Would that affect the sulfite results?

 

[Johnd]

Simmer down scientists!! Whilst I am only a lowly engineer, I too have an opinion.

For me, in my winemaking world, having now conducted, dare I say hundreds, of TA tests, my vote is unequivocally for the pH meter monitored titration. Others may do whatever they like, I use 5 ml of wine, slightly diluted with DI water, have an automatic stirrer, and I've yet to screw one up. It's super easy and the endpoint in reached visibly (meter reading) and audibly (it beeps for us old dudes). This is my opinion.

 

[bionerd]

John, what kind of pH meter do you use? The first one I got was kinda crappy, so I went old school :/

 

[ibglowin]

Great, welcome, nice to have you here!

Didn't mean to be condescending but, you were telling people that using an indicator and your eye is more accurate that a pH meter which is just not true unless you have been doing that analysis for 10 years in a lab.
pH meters have gotten really accurate and really cheap in the last 10 years or so making them the standard for testing acids not only in commercial wine labs but also for the home hobbyist as well.

I will say that i am not a total *****, I have a PhD (from the sciences and with that experience I'm pretty sure I know what a color change looks like). I'm here so that I can learn more about the process from other people, so you don't need to be condescending. I have gotten some great advice from other people that have been more welcoming and willing to have more of a conversation. I'm just saying that both can work. If you have a lot of money and want a super accurate process that's great, use your pH meter.

 

[Johnd]

John, what kind of pH meter do you use? The first one I got was kinda crappy, so I went old school :/

I started out with a meter I purchased online for 25 bucks or so. Once I knew that the wine bug had bitten me and I was indeed infected, I stepped up to the Vinmetrica 300 system.

It comes complete with all that is needed for testing pH, TA and SO2 in my wines, including different sized, graduated measuring pipettes, syringes,magnetic mixer, and a laboratory stand to hold all of the above in place as I titrate. Replacement chems are easy to come by and I replace all once every year just before the fall grapes come out.

The proper analysis and modification of pH and TA is important enough in wine to make the investment sensible for me. If I spend 1500 bucks on the best grapes I can find, I want to do the best job I can as a winemaker. Having already produced 1000+ bottles of wine using the Vinmetrica, the cost per bottle is already about what I pay for a cork.

 

[jburtner]

+1 on the meters. Get a couple $20 ones and eventually a nice one. Use them all and compare regularly with your calibration standards as well as ofher wines / etc....

Cheers!
-johann

 

[Tnuscan]

Totally not sure why you called me out, but here is the first thing that came to my mind about your amusing "manual" A/O scenario: What if one of the human bellows had lots of garlic with lunch? Would that affect the sulfite results?

LOL! I was being silly/funny, just finished a bottle, and was trying to bring in some fun. I'm still a kid at heart. Laughed myself to tears at "human bellows".

 

[bionerd]

Great, welcome, nice to have you here!

Didn't mean to be condescending but, you were telling people that using an indicator and your eye is more accurate that a pH meter which is just not true unless you have been doing that analysis for 10 years in a lab.
pH meters have gotten really accurate and really cheap in the last 10 years or so making them the standard for testing acids not only in commercial wine labs but also for the home hobbyist as well.

Very true, I can definitely see the utility of the meter for those who haven't been "lab rats" lol. My lab head was so completely old school, so he had us doing all the bio techniques from the 80's (worked great but took like 3 days compared to 3 hours) so I suppose I'm and old person at heart still trying to get with the current times

 

[bionerd]

I started out with a meter I purchased online for 25 bucks or so. Once I knew that the wine bug had bitten me and I was indeed infected, I stepped up to the Vinmetrica 300 system.

It comes complete with all that is needed for testing pH, TA and SO2 in my wines, including different sized, graduated measuring pipettes, syringes,magnetic mixer, and a laboratory stand to hold all of the above in place as I titrate. Replacement chems are easy to come by and I replace all once every year just before the fall grapes come out.

The proper analysis and modification of pH and TA is important enough in wine to make the investment sensible for me. If I spend 1500 bucks on the best grapes I can find, I want to do the best job I can as a winemaker. Having already produced 1000+ bottles of wine using the Vinmetrica, the cost per bottle is already about what I pay for a cork.

That system looks awesome! I'm still in the "wow 75 dollars for fruit is pretty expensive" phase in life, but I can see that being a really nice Christmas present to myself once I start doing larger batches. You must have the wine cellar of everyone's dreams!

 

[Johnd]

I can see that being a really nice Christmas present to myself once I start doing larger batches.

Truth be told, I was pining over it for a few months, and Mrs. JohnD got it for me as a present, she's my biggest advocate!! Doesn't hurt that she loves wine too!!

 

[bionerd]

Truth be told, I was pining over it for a few months, and Mrs. JohnD got it for me as a present, she's my biggest advocate!! Doesn't hurt that she loves wine too!!

Now that right there is a keeper!!!

 

[ibglowin]

I still do free SO2 by aeration/oxidation. Very accurate, but time consuming to setup and run. My eyeball for the endpoint detection of course. The Vinemetrica was just coming out at the time I needed to purchase something and it was expensive (still is IMHO), used proprietary chems that were expensive as well so it was a no brainer (for me anyways) to purchase the $99 A/O Rig off Morewine. Chems are dirt cheap and you can be purchased locally for the most part or on the interwebs.

As for good pH meters that won't break the bank, Many here have purchased the Milwaukee brand of meters MW102 etc. and had great reliability. I purchased a Hanna pHep 5 meter 7 years ago and have had great reliability. Paid a whole $89 now up to just under $100 I see.

I recently was starting to second guess my pH readings so I purchased some cleaning solution for proteins (grape, etc.) cleaned the probe retested, still was not feeling like it was right so purchased a new probe for like $50 from Hanna, popped it in and the new probe gave the exact same reading to 0.01pH unit once calibrated so you can trust them if you take care of them properly and calibrate them once a month or each time you use them.

Again, welcome we are glad to have you!

Very true, I can definitely see the utility of the meter for those who haven't been "lab rats" lol. My lab head was so completely old school, so he had us doing all the bio techniques from the 80's (worked great but took like 3 days compared to 3 hours) so I suppose I'm and old person at heart still trying to get with the current times

 

[Ajmassa]

Never in a million years would I think 2 chemists disagreeing about proper TA testing could be so captivating!
I've been testing using the titrate applicator kit. And solely going by it's included instructions, which are vague. I recently bought a $20 pH tester. So I just looked up the proper way to test TA with the meter.
In doing so, I found that I may have been logging the color change incorrectly I think. My instructions called to add the NaOH and stir. But not to stop when a full color change was noted like I have also read. And to keep adding until the color continues to change even more. And stop when the color is no longer changing. I've read conflicting things on when to stop and note the amounts. And the conflicting instruction could differ more than .2% for results.

Also, When using a ph meter and diluting a sample with distilled water (with or without adjusting ph to 8.2) are there certain things to account for since it was diluted ?
Let's get wordy. Ill say it this way. Assume all samples same
-A 15 ml sample with 6 ml of NaOH added for color change is .60% TA
-A 15 ml sample with 6 ml of NaOH added to get ph of 8.2 is also .60%TA
-a 15 ml sample diluted with 30 ml distilled water would still only need 6 ml of NaOH for .60% TA ? Or wouldnitnbe more NaOH needed and there is an adjustment then made to account for this?
- and same for diluted water that was previously adjusted up to ph 8.2?

 

[bionerd]

I'll definitely look into the Hanna pHep 5. If it has been working well that long for you, that must be a good one!

 

[ibglowin]

I have done it both ways, (adjusted my distilled water to 8.2 and left it as is right out of the bottle) The difference is literally a couple drops using 0.1N NaOH. In fact the instructions for TA testing that come with the Morewine TA test kit have no mention of the need to preadjust your distilled water. Its really within the noise of the results. You won't taste any difference in a wine that has a TA of 6.5 g/L or 6.6 g/L in another words.

 

[ibglowin]

Some people (like me) have had great luck, others it has crapped out in a year or so. Maybe I got lucky, IDK but I have always cleaned it afterwords, stored it properly calibrated often just the usual stuff your suppose to do. YMMV as they say but it has been a good one for me. The Milwaukee is certainly more "old school" in nature using BNC connectors and all, but that design makes it also more clunkier and definitely calls for a more traditional setup of stand etc to hold the probe(s) etc. Where as the Hanna is waterproof and floats. Both probes are at the end of the meter and the pH probe is replaceable (plug and play)

I'll definitely look into the Hanna pHep 5. If it has been working well that long for you, that must be a good one!

 

[Ajmassa]

Ok. So bear with me. A 5 ml sample requires to multiply the NaOH amount by 1.5 correct?
And a 15 ml sample does not need any equation. So diluting 15 ml sample with 30 ml of water would yield (essentially) the same result?
Just as diluting 5 ml sample would still just multply by 1.5?
All this assuming a .1 solution. Currently I've been using .2.

 

[ibglowin]

There are a bunch of different TA formula's out there so you have to be careful and use the right amount of wine and the right strength of NaOH or the formula will produce an incorrect answer. The water adds no acid (really) so it doesn't matter how much you add, it won't affect your result enough to matter.

Ok. So bear with me. A 5 ml sample requires to multiply the NaOH amount by 1.5 correct?
And a 15 ml sample does not need any equation. So diluting 15 ml sample with 30 ml of water would yield (essentially) the same result?
Just as diluting 5 ml sample would still just multply by 1.5?
All this assuming a .1 solution. Currently I've been using .2.

 

[bionerd]

Never in a million years would I think 2 chemists disagreeing about proper TA testing could be so captivating!
I've been testing using the titrate applicator kit. And solely going by it's included instructions, which are vague. I recently bought a $20 pH tester. So I just looked up the proper way to test TA with the meter.
In doing so, I found that I may have been logging the color change incorrectly I think. My instructions called to add the NaOH and stir. But not to stop when a full color change was noted like I have also read. And to keep adding until the color continues to change even more. And stop when the color is no longer changing. I've read conflicting things on when to stop and note the amounts. And the conflicting instruction could differ more than .2% for results.

Also, When using a ph meter and diluting a sample with distilled water (with or without adjusting ph to 8.2) are there certain things to account for since it was diluted ?
Let's get wordy. Ill say it this way. Assume all samples same
-A 15 ml sample with 6 ml of NaOH added for color change is .60% TA
-A 15 ml sample with 6 ml of NaOH added to get ph of 8.2 is also .60%TA
-a 15 ml sample diluted with 30 ml distilled water would still only need 6 ml of NaOH for .60% TA ? Or wouldnitnbe more NaOH needed and there is an adjustment then made to account for this?
- and same for diluted water that was previously adjusted up to ph 8.2?

I will start by saying I'm pretty new with wine making (and worked in an old school lab), so I have been treating this more as a "fun chemistry experiment" and using more of my understanding of science as a guide, so I defer to the master wine makers here

but this is essentially the acid base chemistry behind what you are doing:

If titrating wine is your first experience with titrations, I can definitely see how the instructions that come with the kit are not "user friendly." Especially if you are working with red wine where is says to look for a "greyish color" The first time I used that for undiluted cherry I honestly thought what is greyish???? But, if you dilute your wine so that it is only slightly pink, the color change will be a lot easier to see. One problem that people have (from my experience in the lab) is to over titrate. The indicator will change to a bright fuchsia pink once you have reached the end point of the titration, so that is where you would want to stop.

If you are good with indicator based titrations, you should reach the endpoint and have a pH around 8.2. Adding more water shouldnt change the endpoint of the reaction since you are still starting with the same amount of acid, just in a different volume. So you wouldn't need to make any adjustments there. If you are diluting, I would use distilled water or tap water. If you bring the pH of your diluting water up and add it, you are essentially making your starting fluid more basic, which can throw off the results titration (science opinion here, not sure if there is an impact on the wine making science).

For you, I would probably say that the pH mediated titration method would probably give you the best results since it takes the guess work of "did it change color enough" out of the titration. You will probably want to get a stir plate so that your pH meter is reading the pH of the solution (if not properly mixed, your meter could be measuring lower or higher than what the solution should be)

One fun experiment you could do (I plan on doing this too on my next batch to see if my questionable meter is as questionable as it seems) is to titrate with the pH meter but still add indicator. That way you can see what the endpoint would look like with the indicator based method, but still have the precision of the pH meter.

 

[Ajmassa]

Thank you kindly. The ph value of the water had me overthinking it.

Edit. Thank you to both of you that is.