Capillary electrophoresis behavior of water-soluble anionic porphyrins in the presence of beta-cyclodextrin and its O-methylated derivatives.
The electrophoretic behavior of water-soluble anionic porphyrins, such as meso-tetrakis(4-carboxyphenyl) porphyrin (TCPP), meso-tetrakis(4-sulfonatophenyl) porphyrin (TSPP) and its zinc(II) and copper(II) complexes (ZnTSPP and CuTSPP, respectively) has been studied by capillary zone electrophoresis using fused-silica capillaries. The selectivity of the separation is strongly dependent on the type and concentration of betacyclodextrin (betaCD) or the O-methylated derivatives added to the background electrolyte. CuTSPP and TSPP can be separated using a pH 2.5 aqueous sodium phosphate buffer in the presence of 1 mM betaCD. Resolution is poorer or absent employing alkylated betaCDs, such as the heptakis (2,6-di-O-methyl)-beta-cyclodextrin or the heptakis(2,3,6-triO-methyl)-beta-cyclodextrin, as additives. On the other hand, separation of TSPP from its copper and zinc complexes has been achieved using a pH 7.0 aqueous sodium phosphate buffer, in the presence of 0.75 mM betaCD and 20% dimethyl sulfoxide (DMSO) as organic modifier. Under such conditions, the calibration curve for quantitative analysis of copper(II) was obtained. A rationale for the observed behavior will be presented and discussed on the basis of binding and protonation equilibria and a simple mathematical model.
Andrighetto
P
P
Dipartimento di Chimica Inorganica, Metallorganica ed Analitica, Università di Padova, Italy.
Carofiglio
T
T
Fornasier
R
R
Tonellato
U
U
D000838:Anions; D003300:Copper / Q000032:analysis; D003505:Cyclodextrins / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D008745:Methylation; D008962:Models, Theoretical; D011166:Porphyrins / Q000737:chemistry*; D012995:Solubility; D014867:Water; D047392:beta-Cyclodextrins
D000838:Anions; D003505:Cyclodextrins; D011166:Porphyrins; D047392:beta-Cyclodextrins; D014867:Water; D003300:Copper; C031215:betadex