Question

You have made a 20 mM Succinate buffer at pH 5.64 in a 2.0 ml solution to run an enzyme reaction which generates H+. When you finish the reaction, you find the pH has shifted to a pH of 4.0. Much lower than you would like. How would you adjust your buffer to avoid such a significant pH change? You must use succinate buffer and because of the enzyme’s optimal pH requirement you must maintain a pH of 5.64. No calculations are required for this answer, just identify the problem and describe how/what you would do differently. There is a key buffer concept for this question you should identify in your answer.

Answer 1

Succinic acid is a dibasic acid. the pka values for each dissociaiton of hydrogen ions are

pKa1 = 4.2   and pKa2 = 5.6

So we can use succinate buffer but with combination of succinic acid and its monosodium salt. So we can adjust the pH of solution upto 4.2 by adjusting the amount of NaOH added as it will react with succinic acid to give monosodium salt of succinic acid at low concentration of NaOH.

If we add more NaOH then it will generate buffer with pH = 5.6.