≥99% anhydrous basis (titration)

3-(Cyclohexylamino)-2-hydroxy-1-propanesulfonic acid, CAPSO Free Acid
Empirical Formula (Hill Notation):
CAS Number:
Molecular Weight:
Beilstein/REAXYS Number:
MDL number:
PubChem Substance ID:

Quality Level


≥99% anhydrous basis (titration)


crystalline powder



useful pH range

8.9 - 10.3

pKa (25 °C)



water: 0.111 g/mL, clear, colorless

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General description

CAPSO is a useful secondary standard buffer. Second dissociation constant pK2 value of CAPSO has been measured. Useful pH range for CAPSO is 8.9 - 10.3.


CAPSO was used as biological buffer in the following studies:
  • To maintain pH 9 during water leach test for the analysis of high-carbon coal fly ash-soil mixtures.
  • Chemiluminescent in situ hybridization using soybean peroxidase-labeled peptide nucleic acid (PNA) probes. I
  • Preparation of planar bilayer lipid membranes.
It may be employed as buffer for the electrophoretic analyses in non-denaturing gels, to investigate macromolecular self-association of ADP-ribosyltransferase protein in solution.


25, 100, 500 g in poly bottle
1 kg in poly bottle

Personal Protective Equipment

dust mask type N95 (US),Eyeshields,Gloves


NONH for all modes of transport

WGK Germany


Flash Point(F)

Not applicable

Flash Point(C)

Not applicable

Certificate of Analysis

Certificate of Origin

H Stender et al.
Applied and environmental microbiology, 67(1), 142-147 (2001-01-03)
A new chemiluminescent in situ hybridization (CISH) method provides simultaneous detection, identification, and enumeration of culturable Escherichia coli cells in 100 ml of municipal water within one working day. Following filtration and 5 h of growth on tryptic soy agar...
P I Bauer et al.
The Biochemical journal, 270(1), 17-26 (1990-08-15)
The macromolecular self-association of ADP-ribosyltransferase protein in solution was studied by several experimental techniques: quantitative gel filtration, electrophoretic analyses in non-denaturing gels, and cross-linking the enzyme protein with glutaraldehyde, dimethyl pimelimidate, dimethyl suberimidate, dimethyl 3,3'-dithiobisproprionimidate and tetranitromethane. The self-association of...
Second dissociation constants of 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO) from the temperatures 278.15 K to 328.15 K.
Roy RN, et al.
The Journal of Chemical Thermodynamics, 29(7), 749-756 (1997)
Andreas Missner et al.
The Journal of biological chemistry, 283(37), 25340-25347 (2008-07-12)
Several membrane channels, like aquaporin-1 (AQP1) and the RhAG protein of the rhesus complex, were hypothesized to be of physiological relevance for CO(2) transport. However, the underlying assumption that the lipid matrix imposes a significant barrier to CO(2) diffusion was...
Evaluation of leaching protocols for testing of high-carbon coal fly ash-soil mixtures.
Becker J, et al.
Journal of Environmental Engineering (New York, N.Y.), 139(5), 642-653 (2012)

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