Dear Parham, dear Rastislav,

both of you are right (at least in part)....  Problems I have with your suggestions:

(not to teach you!)

1) @Parham: if you have diluted your original mixture (as you wrote: "and after adding more than 5L [NB: 5 LITERS!!] of acetic acid 0.4 M solution to 80 ml of sodium acetate 0.4, the acetate buffer with the pH of 3 was achieved!" ) this way to end up with a pH of 3, you missed your goal to have a 0.4M buffer solution.

2) The principal premise of a buffer is "to exert buffer capacity over a certain range of pH", and therfore there are buffer solutions with different composition (ingredients) to achieve such: e.g.:

Range of common buffer systems

Buffering system                                                   Useful buffering pH range @ 25°C

Hydrochloric acid/ Potassium chloride                               1.0 - 2.2

Glycine/ Hydrochloric acid                                                     2.2 - 3.6

Potassium hydrogen phthalate/ Hydrochloric acid           2.2 - 4.0

Citric acid/ Sodium citrate                                                      3.0 - 6.2

Sodium acetate/ Acetic acid                                                   3.7 - 5.6

and so on. 

3) as you can see, usually Sodium acetate/acetic acid buffer system is ideally when buffering range is within 3.7 to 5.6.

4) therefore Rastislav is right in two ways: i) for a "functional buffer solution at pH 3.0" one better uses perhaps a citric acid/sodium citrate buffer and ii) perhaps also concerning the molarity of the buffer solution (dissociation).

5) Nevertheless there exist some recipes (or at least one) for Acetate buffer solution(s) (Sodium acetate/Acetic acid) for pH 3.0, unfortunately only for Molarity = 0.1 M or 0.2 M. I do not know whether one can use "similar" volumetric calculations if using 0.3 M stock solutions:

Acetate buffer solutions pH 3 - 6 ³

Make up the following solutions (1) 0.1M acetic acid (2) 0.1M sodium acetate (tri-hydrate) (13.6g / l) Mix in the following proportions to get the required ph

pH                        vol. of 0.1M acetic acid            vol. of 0.1M sodium acetate

3                                 982.3 mls                                         17.7 mls

4                                 847.0 mls                                         153.0 mls

5                                 357.0 mls                                         643.0 mls

6                                 52.2 mls                                           947.8 mls

or:

SODIUM ACETATE; PH 3.6–5.6, PKA = 4.76

Combine the following proportions of 0.1N acetic acid and 0.1N sodium acetate (Pearse, 1980).

 acetic acid   sodium acetate   pH

185              15                       3.6

176              24                       3.8

164              36                       4.0

147              53                       4.2

126              74                       4.4

102              98                       4.6

80                120                     4.8

59                141                     5.0

42                158                     5.2

29                171                     5.4

19                181                     5.6

or:

Acetate Buffer (only down to a pH of 3.6, this also in concordance with Rastislavs suggestion)

Stock Solutions:

A: 0.2 M solution of acetic acid (11.55 ml in 100 ml of distilled water)

B: 0.2 M solution of sodium acetate (16.4 g of C2H3O2Na   or 27.2 g of C2H3O2Na·3H2O   in 1000 ml of distilled water)

x ml of A plus y ml of B       and diluted to a total of 100 ml with distilled water:

x                      y                      pH

46.3                3.7                  3.6

41.0                9.0                  4.0

30.5                19.5                4.4

20.0                30.0                4.8

14.8                35.2                5.0

10.5                39.5                5.2

4.8                  45.2                5.6 .

Lower pH buffer systems eg.

CITRATE BUFFER; PH 3.0–6.2, PKA = 6.40 Citrate buffer (Gomori, 1955)  or GLYCINE–HCL; PH 2.2–3.6, PKA = 2.35 (Dawson, et al., 1969)    or PHOSPHATE–CITRATE BUFFER; PH 2.2–8.0, PKA = 7.20/6.40 (Pearse 1980)

certainly would be an option, but unfortunately we do not know about the real purpose of nedding and/or using Acetate Buffer pH 3.0.

I wave downvoting the question or even the reply of Parham (because the attempt really is of no value at all)  since the matter really is too important to be deleted from the topic "buffers" and/or buffer preparation.

Sources I have included, others from web-files (I would have to dig for their original URL).

Regards,

Wolfgang

NB: if those columns will get chaotic after adding my answer here, I should post another reply including an attached pdf to this thread)

Dear Parham,

It is imposible to prepare a buffer with pH 3 from acetic acid, or from its mixture with sodium acetate, regardless their ratio or concentrations.  The reason is low dissociation constant of CH3COOH, aproximately equal to 1.8  x 10-5 . Off more, sodium acetate dissolved in water is hydrolyzed  to NaOH /strong base/ and CH3COOH /weak acid/, and pH of its solution  is over 7. 

Best regards.

Note: you should rather use a mixture of 0.1M citric acid /a/  with 0.2M Na2HPO4 /b/ .   Mix  15.89 ml of solution /a/ with  4.11 ml of solution /b/. The pH in this case is 3.00 in temperature interval from 15 to 30 oC.

Dear Rastislav SOLÁR

Thank you very much for your response. I just made two separate solutions of acetic acid and sodium acetate with molarity of 0.4. Then I chose 80 ml of sodium acetate 0.4 M as base (pH was over 8). Then I add acetic acid 0.4 M solution to it dropwise (Titration). After about 10 minutes, I found out that the pH was going down very slowly, So I speed up the adding of acetic acid and after adding more than 5L of acetic acid 0.4 M solution to 80 ml of sodium acetate 0.4, the acetate buffer with the pH of 3 was achieved! It was the real buffer, cause the pH was resisting as hell!

Once again I want to thank you and appreciate your time.

That is OK Parham.

I hope not to offend you, answering the question I did not ask you to upvote /or downvote/ the quality of the answer.

Next time you should upvote the answer  if it was competent and posiibly useful, or downvote it if it was not.

Best regards,

R.S.

Dear Parham,

thank you.

What have you used to determine the pH, was it a pH meter? Was the instrument calibrated on some reference buffer in and acidic region of pH /0 to 7 pH units/? Youll save much time and chemicals when using that citrate 0.1M / disodium phosphate 0.2M  mixed buffer as I advised to you.

Good luck,

R.S.

Dear Parham, dear Rastislav,

both of you are right (at least in part)....  Problems I have with your suggestions:

(not to teach you!)

1) @Parham: if you have diluted your original mixture (as you wrote: "and after adding more than 5L [NB: 5 LITERS!!] of acetic acid 0.4 M solution to 80 ml of sodium acetate 0.4, the acetate buffer with the pH of 3 was achieved!" ) this way to end up with a pH of 3, you missed your goal to have a 0.4M buffer solution.

2) The principal premise of a buffer is "to exert buffer capacity over a certain range of pH", and therfore there are buffer solutions with different composition (ingredients) to achieve such: e.g.:

Range of common buffer systems

Buffering system                                                   Useful buffering pH range @ 25°C

Hydrochloric acid/ Potassium chloride                               1.0 - 2.2

Glycine/ Hydrochloric acid                                                     2.2 - 3.6

Potassium hydrogen phthalate/ Hydrochloric acid           2.2 - 4.0

Citric acid/ Sodium citrate                                                      3.0 - 6.2

Sodium acetate/ Acetic acid                                                   3.7 - 5.6

and so on. 

3) as you can see, usually Sodium acetate/acetic acid buffer system is ideally when buffering range is within 3.7 to 5.6.

4) therefore Rastislav is right in two ways: i) for a "functional buffer solution at pH 3.0" one better uses perhaps a citric acid/sodium citrate buffer and ii) perhaps also concerning the molarity of the buffer solution (dissociation).

5) Nevertheless there exist some recipes (or at least one) for Acetate buffer solution(s) (Sodium acetate/Acetic acid) for pH 3.0, unfortunately only for Molarity = 0.1 M or 0.2 M. I do not know whether one can use "similar" volumetric calculations if using 0.3 M stock solutions:

Acetate buffer solutions pH 3 - 6 ³

Make up the following solutions (1) 0.1M acetic acid (2) 0.1M sodium acetate (tri-hydrate) (13.6g / l) Mix in the following proportions to get the required ph

pH                        vol. of 0.1M acetic acid            vol. of 0.1M sodium acetate

3                                 982.3 mls                                         17.7 mls

4                                 847.0 mls                                         153.0 mls

5                                 357.0 mls                                         643.0 mls

6                                 52.2 mls                                           947.8 mls

or:

SODIUM ACETATE; PH 3.6–5.6, PKA = 4.76

Combine the following proportions of 0.1N acetic acid and 0.1N sodium acetate (Pearse, 1980).

 acetic acid   sodium acetate   pH

185              15                       3.6

176              24                       3.8

164              36                       4.0

147              53                       4.2

126              74                       4.4

102              98                       4.6

80                120                     4.8

59                141                     5.0

42                158                     5.2

29                171                     5.4

19                181                     5.6

or:

Acetate Buffer (only down to a pH of 3.6, this also in concordance with Rastislavs suggestion)

Stock Solutions:

A: 0.2 M solution of acetic acid (11.55 ml in 100 ml of distilled water)

B: 0.2 M solution of sodium acetate (16.4 g of C2H3O2Na   or 27.2 g of C2H3O2Na·3H2O   in 1000 ml of distilled water)

x ml of A plus y ml of B       and diluted to a total of 100 ml with distilled water:

x                      y                      pH

46.3                3.7                  3.6

41.0                9.0                  4.0

30.5                19.5                4.4

20.0                30.0                4.8

14.8                35.2                5.0

10.5                39.5                5.2

4.8                  45.2                5.6 .

Lower pH buffer systems eg.

CITRATE BUFFER; PH 3.0–6.2, PKA = 6.40 Citrate buffer (Gomori, 1955)  or GLYCINE–HCL; PH 2.2–3.6, PKA = 2.35 (Dawson, et al., 1969)    or PHOSPHATE–CITRATE BUFFER; PH 2.2–8.0, PKA = 7.20/6.40 (Pearse 1980)

certainly would be an option, but unfortunately we do not know about the real purpose of nedding and/or using Acetate Buffer pH 3.0.

I wave downvoting the question or even the reply of Parham (because the attempt really is of no value at all)  since the matter really is too important to be deleted from the topic "buffers" and/or buffer preparation.

Sources I have included, others from web-files (I would have to dig for their original URL).

Regards,

Wolfgang

NB: if those columns will get chaotic after adding my answer here, I should post another reply including an attached pdf to this thread)

Dear Wolfgang H. Muss

Oh wow! You are awesome. Thank you very much!

According to the attached PDF (page 6), determination of azithromycin antibiotic concentration using spectrophotometric method, needs 0.4M Acetate buffer (pH 3).

I don't know if I can use any alternative buffers for this specific purpose and for this reason I am insisting on preparing exactly the reported buffer.

Best Regards

Dear Parham Akhlaghi,

 I have seen the notation (not only for azithromycin) in the pdf you enclosed previously.

 As I said previously: “not to teach you”! for me it is not understandable how such a statement and instruction could be / was included in this textbook (and not only once!, see the following paragraphs for other antibiotics).

Fact is that has its “buffering capacity” between pH 3.6 and 5.6 according to most of the recipes/tables one can find.

Besides the achievable pH, additional issues certainly are ionic strength and dissociation (0.1M > 0.4M).

I won't dodge something here so I have checked on weekend several sources and articles by Googleing.

What I have found I attach in the separate pdf with my reply (just not to bother other viewers or posters)

Best wishes and regards,

Wolfgang

Dear Wolfgang!

You really helped me! Thank you very much. I just finished writing my thesis and I'm gonna have my defense session on Monday! I really appreciate your time for helping me.

Thank you :)

Dear Parham, you are welcome and "Good luck"...hope you have finished the defense session successfully ...

Best regards,

Wolfgang

Does anyone know how to prepare the acetate buffer with a molarity of 0,3 M at pH 3,6? This is for a FRAP test.

Thanks!

Dear Paula....

I just googled < FRAP test  > (because retirement for now 1 month made me a bit silly...) and guess what I found in one of the first results:

ex pdf: (available already on ResearchGate)   

  in: ANALYTICAL BIOCHEMISTRY 239, 70–76 (1996)

ARTICLE NO. 0292,  by Iris F. F. Benzie*,1 and J. J. Strain

CITATION (p. 71): 

PubMed:  www.ncbi.nlm.nih.gov/pubmed/8660627

I haven't (re-) calculated the measures given in Benzie and Strain's Article...but think for acatetate buffer  there are calculatory tables available....

Best wishes and good luck - and naturally: HAppy, healthy, prosperous and success- and joyful  NEW YEAR !

Wolfgang

 Paula, its me again...

I've just searched Google "with pain", i. e. Google search phrase was: 

  < RECIPE acetate buffer  0,3 M at pH 3,6 AND  FRAP test >

and one can find some articles using the buffer you need...  but most of them don''t say HOW the 0,3M-acetate buffer pH 3.6 is made. 

As I cited in Re# 11 above the article of BENZIE Iris FF, I would like to add the source/URL in ResearchGate(postfileloader...):

https://www.researchgate.net/researcher/9416577_Iris_FF_Benzie

You can do a publications-Research [see in this or YOUR PROFILE in the upper menue line right to "JOBS",:  find the scroll menue "search", indicate  "publications" and insert at least 4-6 words of the title you are searching for...

The articele URL of BENZIE and STRAIN is: https://www.researchgate.net/publication/14539362_The_Ferric_Reducing_Ability_of_Plasma_FRAP_as_a_measure_of_antioxidant_power_The_FRAP_assay

I found another source, displaying the preparation/recipe of the buffer you need:

Go to:     http://archive.lib.cmu.ac.th/full/T/2012/phars30312rp_ch3.pdf , find

3.4.3 Ferric reducing antioxidant power (FRAP assay) [42]

3.4.3.1 FRAP working solution preparation

(CTRL-F:  and insert:  acetate  )

Citation:

Unfortunately I was not able to find an author or the title of the paperwork including that

I nevertheless ope that these two recipes I found give rise to successful preparations,

best regards and wishes,

Wolfgang

Article The Ferric Reducing Ability of Plasma (FRAP) as a measure of...

Thank you Pr Wolfgang, .

I would like to thank you for your quick answer !

Yes, I could realize that most of the articles omit that little information about the preparation of the acetate that is less common from 0,1 or 0,2M as you said it before in this discussion.

I prepared as it was proposed from another source with 1,86g with anhydrous sodium acetate and 16 mL in 1000 mL of solution.

However the pH  was close to 3,47. Because the desired pH is 3,6, I have had always the question if I can complete it with a little of 0,3 M of sodium acetate solution?

Hoping that you have a happy retirement and a new year full of joy and peace.

Best regards,

Paula

I add the link where I found the information :

https://books.google.ca/books?id=12qhyOW2EewC&pg=PA207&lpg=PA207&dq=acetate+buffer+0.3M+at+pH+3.6&source=bl&ots=zsOckx1xDh&sig=5Kd5NY5kCROMV2GK0XduJK9rs_c&hl=es-419&sa=X&ved=0ahUKEwj31ZrGrf_JAhWE6IMKHZeNAI8Q6AEIPTAE#v=onepage&q=acetate%20buffer%200.3M%20at%20pH%203.6&f=false

Dear Wolfgang,

Your answer is the correct way of making Acetate buffer. However, I was wondering what if you start with a known concentration (say 0.2 M) of acetic acid and then adjust pH to the desired pH using NaOH, and subsequently dilute the solution using water to the desired molarity (say 0.1 M for acetate). Is this also a valid method of making acetate buffer, if not then why not?

Thanks,, Sanjay

Hoping this my reply "gets through"

Dear Paula, sorry for late reply (very briefly):

will answer as soon as possible, just have some troubles with my Internet-access (new PC)... so, please, be patient.

Dear Wolfgang

                  I have a different problem. I have sodium acetate buffer of pH 5.2 and of 3M concentration. Now i want to use sodium acetate buffer of pH 5.2 but its concentration should be 0.2 M. Is it possible by dilution using water or acetic acid, please

What equation would be used for such problems, Please.

thank you

Best

Harinder