Oligomers-model building in protonation equilibria of sitagliptin
| Autor: | Irena Niesnerová, Milan Meloun, Tomáš Pekárek, Zuzana Ferenčíková |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
protonation constant
Chemistry Dimer Potentiometric titration Analytical chemistry Ionic bonding Protonation General Chemistry dimer regression analysis Sitagliptin Phosphate chemistry.chemical_compound ph-titration curve fitting Materials Chemistry Curve fitting sitagliptin phosphate Regression diagnostic Nonlinear regression QD1-999 |
| Zdroj: | Open Chemistry, Vol 11, Iss 11, Pp 1799-1807 (2013) |
| ISSN: | 2391-5420 |
| Popis: | Mixed protonation constants of sitagliptin phosphate at various ionic strengths I (mol kg−1) in range 0.01 and 0.50 and at 298.15 K are determined using FBSTAC4 and HYPERQUAD nonlinear regression analyses of the potentiometric titration curve. At a low concentration c L = 1.1 mmol kg−1 the monomers L, LH, LH2, LH3 and LH4 dominate, while for a concentration range from c L = 13.7 to 24.7 mmol kg−1 dimers L2H2, L2H3, L2H4 and L2H are mainly present. The regression programme has almost no influence on the precision of the protonation constants. The accuracy of the protonation constants log βqr depends on the accuracy of the group parameters. As two group parameters c L,0, c H,T are ill-conditioned in a model, their determination is therefore uncertain: both can significantly cause a systematic error in the estimated common parameters log10βqr . Fitness tests using regression diagnostics have proven the reliability of the parameter estimates. |
| Databáze: | OpenAIRE |
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