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Capillary electrophoresis behavior of water‐soluble anionic porphyrins in the presence of β‐cyclodextrin and its O ‐methylated derivatives
Author(s) -
Andrighetto Paolo,
Carofiglio Tommaso,
Fornasier Roberto,
Tonellato Umberto
Publication year - 2000
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/(sici)1522-2683(20000201)21:3<619::aid-elps619>3.0.co;2-y
Subject(s) - chemistry , capillary electrophoresis , cyclodextrin , aqueous solution , copper , protonation , zinc , porphyrin , dimethyl sulfoxide , electrolyte , inorganic chemistry , selectivity , chromatography , organic chemistry , ion , electrode , catalysis
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 β‐cyclodextrin (βCD) 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 m M βCD. Resolution is poorer or absent employing alkylated βCDs, such as the heptakis (2, 6‐di‐ O ‐methyl)‐β‐cyclodextrin or the heptakis(2,3,6‐tri‐ O ‐methyl)‐β‐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 m M βCD 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.