title: Estimation of pK(a) values using microchip capillary electrophoresis and indirect fluorescence detection.
abstract: Microchip capillary electrophoresis (CE), coupled with indirect fluorescence detection was investigated for estimating the pK(a) values of non-fluorescent compounds. The CE method is based on the differences in electrophoretic mobility of the analyte as a function of the pH of the running buffer. Nine compounds were tested, including several of pharmaceutical importance, with pK(a) values from 10.3 to 4.6. All buffers contained 5-TAMRA as the fluorescent probe for indirect detection. Calculated pK(a) values agreed well with literature values obtained by traditional methods, differing not more than 0.2 from the literature value. The current work on single lane chips demonstrates the principle of microchip CE with indirect detection as a viable method for estimating pK(a) values. However, increased throughput will be required using a multilane chip to enable the approach to be used practically.
authors.affiliation: Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA.
authors.forename: Christa A
authors.initials: CA
authors.lastname: Currie
authors.forename: William R
authors.initials: WR
authors.lastname: Heineman
authors.forename: H Brian
authors.initials: HB
authors.lastname: Halsall
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Seliskar
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Limbach
authors.forename: Francisco
authors.initials: F
authors.lastname: Arias
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Wehmeyer
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002927:Cimetidine / Q000737:chemistry; D046209:Electrophoresis, Microchip / Q000379:methods*; D005013:Ethosuximide / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010880:Piperidines / Q000737:chemistry*; D011318:Prilocaine / Q000737:chemistry; D011343:Procaine / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D011899:Ranitidine / Q000737:chemistry; D015203:Reproducibility of Results; D012235:Rhodamines / Q000737:chemistry*; D000077145:Sulfanilamide; D013424:Sulfanilamides / Q000737:chemistry; D014498:Uracil / Q000737:chemistry
chemical_list: C420543:5-(N-pipyridyl-4-O-(2-cyanoethyl diisopropylphosphoramidite))-tetramethyl rhodamine carboxamide; D000814:Aniline Compounds; D005456:Fluorescent Dyes; D010880:Piperidines; D011725:Pyridines; D012235:Rhodamines; D013424:Sulfanilamides; D011318:Prilocaine; D000077145:Sulfanilamide; D011343:Procaine; D014498:Uracil; D005013:Ethosuximide; C007106:gamma-collidine; D002927:Cimetidine; D011899:Ranitidine; C023650:aniline