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How to make 0.2 M Tris-Acetate Buffer pH 6

  1. Sep 28, 2016 #1

    asy

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    Hello,

    I need to make a 0.2 M Tris-Acetate Buffer pH 6 and I can't find a protocol for this specific buffer.

    I know that I can make a Tris solution (i.e. 12.11 g of tris(hydroxymethyl)aminomethane in water), adjust the pH to 8 and dilute to 1000 mL with water.

    Is the same true for pH 6?

    Thanks for the help
    Regards
     
  2. jcsd
  3. Sep 28, 2016 #2

    Borek

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    Staff: Mentor

    TRIS acetate at pH 6 doesn't make sense, you are outside of the buffering range of both acetate buffer and TRIS based buffer. Quite likely that's why you can't find the recipe. Technically it is possible to prepare a solution containing both acetate and TRIS and having pH of 6, it just won't be a buffer.
     
  4. Sep 28, 2016 #3

    asy

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    Thanks for the feedback.
    I'm trying to use a method that I found in the literature, which was cited in several papers.

    Folk JE and Cole PW (1966) The Journal of Biological Chemistry 241(23): 5518–5525

    "Each test was made in a final volume of 0.5 ml of 0.2 M Tris-acetate buffer, pH 6.0, containing 0.1 M hydroxylamine, 5 mM CaCl2, 10 mM GSH, and 30 mM CBZ-n-glutaminylglycine. After a 5 or 10 min incubation with the enzyme at 37 ºC, 0.5 ml of ferric chloride-trichloracetic acid reagent was added, and the resulting red color was measured at 525 nm."

    Any suggestion how to proceed?
    Thanks
     
  5. Sep 28, 2016 #4

    Borek

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    Staff: Mentor

    You can't go wrong with adjusting the final pH with the pH meter.
     
  6. Sep 30, 2016 #5

    asy

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    Thank you for the help!
     
  7. Sep 30, 2016 #6

    epenguin

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    Homework Helper
    Gold Member

    Yes the tris would be a poor buffer more than 2 units below its pKa.

    But oh dear, the hydroxylamine has a pKa close to 6, and that is what must be doing most of the buffering during whatever reaction you are following. Just try doing whatever you are doing making your solution pH 6 without any tris! And tell us.
     
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