Question

How many Good's buffer agents exist?

Answer 1

There are 20 Good’s Buffer which have a pKa ranging from 6.1 to 8.5. These Good’s Buffer were selected on the basis of various factor like solubility, pKa range, minimum salt interaction etc.

Complete step-by-step answer: Let us first talk about Good’s Buffer agents:-
In the year of 1966, Norman Good and his colleagues set out to define the best buffers for biochemical systems based on various factors as follows:-
-The Good’s buffer should have a pKa between 6.1 and 8.5
-Should be soluble in water.
-Minimal interactions with the salt used.
-Should have minimum effects on the dissociation from changes in temperature and concentration.
-The buffer needs to be stable and not break down under working conditions.
-The buffer components should be easy to obtain, prepare and use.

The buffers, with their pKa values, are:-
-MES: 2-(N-morpholino) ethanesulfonic acid - 6.15
-ADA: N-(2-acetamido) iminodiacetic acid - 6.62
-PIPES: piperazine-$N,N'$-bis(2-ethanesulfonic acid) - 6.82
-ACES: N-(2-acetamido)-2-aminoethanesulfonic acid - 6.88
-MOPSO: 3-(N-morpholinyl)-2-hydroxypropanesulfonic acid - 6.95
-Cholamine chloride: $({{(C{{H}_{3}})}_{3}}{{N}^{+}}C{{H}_{2}}C{{H}_{2}}N{{H}_{2}})C{{l}^{-}}$ - 7.10
-BES: $N,N'$-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid - 7.17
-MOPS: 3-(N-morpholino)propanesulfonic acid -7.20
-TES: N-[tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid - 7.40
-HEPES: 4-(2-hydroxyethyl)-1-piperazinylethanesulfonic acid - 7.48
-DIPSO: $N,N'$-bis(2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid - 7.60
-TAPSO:3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid - 7.60
-Acetamidoglycine: $C{{H}_{3}}CONHNHC{{H}_{3}}COOH$- 7.7
-POPSO: piperazine-$N,N'$-bis(2-hydroxypropanesulfonic acid) - 7.85
-HEPPSO: 4-(2-hydroxyethyl)piperazine-1-(2-hydroxypropanesulfonic acid) -7.85
-HEPPS: 3-[4-(2-hydroxyethyl)-1-piperazinyl]propanesulfonic acid - 8.00
-Tricine: N-[tris(hydroxymethyl)methyl)]glycine - 8.15
-Glycinamide: $N{{H}_{2}}C{{H}_{2}}CON{{H}_{2}}$ - 8.20
-Bicine: $N,N'$-bis(2-hydroxyethyl)glycine - 8.35
-TAPS: N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid - 8.44

Note: Remember that no matter what buffer we choose, we always need to consider effects of temperature and environment on the buffer and ensure that the buffer is compatible with our system. Also, concentration factor has a great role in affecting pKa.