How do you prepare a borate buffer (100 mM borate, 150 mM NaCl, pH 9)? How would I know what system to use (e.g. boric acid-NaOH, sodium tetraborate-HCl, boric acid-sodium tetraborate, etc.) if it is not specified in the literature? I am planning to use it on silk fibroin solution.
You can use any system you mentioned. Considering the high pH I would use the borate-HCl. Add appropriate masses of borate and NaCl, dissolve in water, adjust pH to 9.0 with HCl and dilute to final volume. Remember you are creating a mixture of boric acid and its conjugate base.
See the Henderson-Hasselbalch equation: pH = pKa + log ([A-]/[HA])
You can use any system you mentioned. Considering the high pH I would use the borate-HCl. Add appropriate masses of borate and NaCl, dissolve in water, adjust pH to 9.0 with HCl and dilute to final volume. Remember you are creating a mixture of boric acid and its conjugate base.
See the Henderson-Hasselbalch equation: pH = pKa + log ([A-]/[HA])
Is sodium borate the same as sodium tetraborate? Sigma doesn't sell Sodium Borate.
Here is a dicussion of the borate buffer system.
http://www.crscientific.com/experiment4.html
Here are some links which will provide you to how to prepare borate buffer:
http://www.novedu.ru/anotes/refer/buffers.htm
http://forum.claritytechniques.org/discussion/52/1%E2%80%89m-sodium-borate-buffer-solution
Start from borax (beware it has cryst water!!!); add NaCl and adjust the pH with diluted HCl or NaOH. For your purpose, if the buffer is 102 mM in borate will not be as harmful as if the pH is 9,2
Teodoro, are there any safety precautions that should be done since it is hydrated?
Borate Buffer
· 1. 4.76 g Boric Acid (Cat # B-1934)
· 2. 2.54 g Borax (Cat # B-0127)
· 3. 1000 mL of ddH2O
· 4. pH to 8.4 with NaOH
· 5. Sterile Filter
Hi, May I know, what factors should I look up to choose my buffer solution?
I want to make buffer in pH 11 and pH 9.. can i choose one pH with phosphate buffer and the other one with borate buffer???
Many factors you might want to consider are summarized here:
http://www.reachdevices.com/Protein/BiologicalBuffers.html
- Prepare a solution of 4 M NaOH
- For 1 l of buffer:
weigh off 100 mmol of boric acid (MW of boric acid is 61,8 g/mol, so weigh off 6.18 g) in a 1l beaker
- weigh off 150 mol NaCl (MW of NaCl is 58,4 g/mol, so weigh off 8,76 g) and add to the same beaker
- add approximately 900 ml of water.
- Calibrate a pH meter, insert the pH electrode in the solution while stirring with an electric stirrer . Slowly add drops of the concentrated NaOH solution till the desired pH. Due to the low solubility of boric acid, the solution is cloudy in the beginning but clears up as pH becomes higher (eventually heat to fasten dissolution but not higher than 30°C as pH is temperature sensitive).
- transfer the liquid to a 1l measuring cilinder and adjust to 1 l with water. Because a buffer solution does not change pH upon diluting, the pH remains the same.
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