. 2010 Apr 1;6:31. doi: 10.3762/bjoc.6.31

Table 1.

pK_a comparison of aminoalkylsulfonates. Acronyms refer to compounds in the Good’s buffer series that are commercially available. Some of the less common ones are CHES [2-(cyclohexylamino)ethanesulfonic acid], EPPS [4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid], PIPPS [piperazine-N,N′-bis(3-propanesulfonic acid], and CAPS [3-(cyclohexylamino)-1-propanesulfonic acid]. Experimental values reported at or above precision of measurement (see Supporting Information for statistics).

	pK_a	Ethyl analog	pK_a^a	Propyl analog	pK_a^a

1	3.9	MES	6.2	MOPS	7.2
2	7.9	HEPES	7.5	EPPS	8.0
3	4.9^b	PIPES	6.8^b	PIPPS	8.0^b
4	7^c	CHES	9.3	CAPS	10.4

^aValues from references [1,5,7].

^b2^nd (ammonium) dissociation constant value.

^cEstimate only (precipitates at pH ≈ pK_a).