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Specialty Chemistry Forums => Materials and Nanochemistry forum => Topic started by: Calamiteh on February 25, 2022, 12:15:02 PM

Title: 1M, 7.3 pH Tris-HCL Buffer solution
Post by: Calamiteh on February 25, 2022, 12:15:02 PM
Hello. I have been trying to mix up a 1 M, 7.3 pH Tris HCl buffer using Trizma Base and Trisma Hydrochloride. During my research, I stumbled upon a website that calculated the weight of each component I need to dissolve in order to achieve my wanted outcome. I haven't tried it out yet however, I was wondering if anyone can help me to figure out how the certain amounts can be calculated. I've been trying to use the Henderson-Hasselbach buffer equation but I haven't been able so far to reproduce the results. I am aware that the website only spits out the results for 0.1 M buffer but changing the values accordingly to achieve 1M isn't that big of a deal. I just want to understand how the specific amounts of Trizma Base and Trizma HCl are calculated.

Any help would be greatly appreciated.
(https://i.imgur.com/NTMMWed.png)
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2F&hash=03ee70165653ed1fcf3a617a5e4320ea)
Title: Re: 1M, 7.3 pH Tris-HCL Buffer solution
Post by: Borek on February 25, 2022, 01:42:14 PM
Numbers look quite accurate.

From molarity and volume calculate number of moles of both Tris forms, from HH equation calculate their ratio. Converting to masses is rather trivial.
Title: Re: 1M, 7.3 pH Tris-HCL Buffer solution
Post by: jeffmoonchop on February 25, 2022, 10:50:03 PM
Just add 1M worth of Tris base then pH adjust down with HCl.
Title: Re: 1M, 7.3 pH Tris-HCL Buffer solution
Post by: Babcock_Hall on March 01, 2022, 09:24:24 AM
The apparent pKa of TrisH+ will be different at 1.0 M buffer strength than 0.1 M.  There is a formula to estimate the correction as a function of ionic strength that I saw on page 30 of the book Buffer Solutions the Basics, by Beynon and Easterby. However, I would not be certain that this formula works at such a high concentration, and I would defer to Borek on that question.  Jeffreymoonchop's suggestion is reasonable.  EDT: More specifically I would add slightly less volume of water than the final solution volume, add HCl to the correct pH, then bring to the final volume with a small additional portion of water.
Title: Re: 1M, 7.3 pH Tris-HCL Buffer solution
Post by: Borek on March 01, 2022, 10:34:51 AM
Quote from: Babcock_Hall on March 01, 2022, 09:24:24 AM
There is a formula to estimate the correction as a function of ionic strength that I saw on page 30 of the book Buffer Solutions the Basics, by Beynon and Easterby.

That's just a variant of Debye-Huckel, it works reasonably well for ionic strengths of about 0.1 (perhaps even a bit higher, as usual it depends on what accuracy is required), so would be applicable for 0.1M buffer only.