- cIEF for rapid pKa determination of small molecules: a proof of concept.
cIEF for rapid pKa determination of small molecules: a proof of concept.
European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences (2014-07-06)
Stéphanie Romand, Julie Schappler, Jean-Luc Veuthey, Pierre-Alain Carrupt, Sophie Martel
PMID24995703
ABSTRACT
A capillary isoelectric focusing (cIEF) method was developed for the determination of the ionization constants (pKa) of small molecules. Two approaches used to decrease the electroosmotic flow (EOF) were compared: (i) a hydroxypropylcellulose (HPC) coated capillary in aqueous medium and (ii) the addition of glycerol to act as a viscosifying agent. The cIEF method with the glycerol medium was selected, and the ionization constants of 22 basic and 21 acidic compounds, including 15 pharmaceutical drugs, were determined, resulting in pKa values from 3.5 to 7.4 and 6.4 to 9.3, respectively. cIEF offers an interesting alternative to other techniques for pKa determination with low sample consumption, high throughput and low cost.
MATERIALS
Product Number
Brand
Product Description
Sigma-Aldrich
Methanol solution, NMR reference standard, 4% in methanol-d4 (99.8 atom % D), NMR tube size 3 mm × 8 in.
Sigma-Aldrich
8-Octanoyloxypyrene-1,3,6-trisulfonic acid trisodium salt, suitable for fluorescence, ≥90% (HPCE)
Sigma-Aldrich
Dimethyl sulfoxide, meets EP testing specifications, meets USP testing specifications