Second dissociation constant and pH of the amino acid buffers CAPSO and MOPSO from 5 to 55°C

CHED 200

Shahaf Ashkenazi, sashkenasi@drury.edu, Sean R. LeNoue, slenoue@drury.edu, Brett T. Morris, bmorris@drury.edu, Lakshmi N. Roy, lroy@drury.edu, and Rabindra N. Roy, rroy@drury.edu. Walter H. Hoffman Department of Chemistry, Drury University, 900 N. Benton Ave., Springfield, MO 65802
The thermodynamic second dissociation constant, pK2 and pH of CAPSO and MOPSO have been determined from emf measurements of hydrogen-silver chloride cells without liquid junction of the type: Pt; H2(g, 1 atm) | CAPSO (m1) + NaCAPSOate (m2) + NaCl (m3) | AgCl, Ag. Measurements were made from 5 to 55°C at 5° intervals. The values of pK2, the thermodynamic quantities (ΔG°, ΔS°, ΔH°, and ΔCp°) have been calculated. The pH values have been calculated using (i) Debye-Hückel extended equation, (ii) Bates-Guggenheim convention, and the Pitzer ion interaction theory for γCl-. The results will be explained in terms of the activity coefficient of zwitterions, solvation of the species, and standard buffer for physiological use.
 

Undergraduate Research Poster Session: Analytical Chemistry
2:30 PM-4:30 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Poster

Division of Chemical Education

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006