Determination of the binding constant of indomethacin-beta-cyclodextrin complex by capillary electrophoresis: experimental optimization and temperature study.
The apparent electrophoretic mobilities of indomethacin in beta-cyclodextrin at a range of concentrations were measured directly by capillary electrophoresis. Three different linear plots and a non linear plot are proposed for the apparent binding constant calculations, based on the fact that the molar ratio of the inclusion complex was 1:1. K values obtained at 298 K were 421 M(-1) (double reciprocal fit), 488 M(-1) (x-reciprocal fit), 428 M(-1) (y-reciprocal fit) and 490 M(-1) (non linear fit). The corresponding K values at 313 K were 380 M(-1) (double reciprocal fit), 355 M(-1) (x-reciprocal fit), 366 M(-1) (y-reciprocal fit) and 339 M(-1) (non linear fit). Using the proposed methods, the binding constant of the indomethacin-beta-cyclodextrin inclusion complex can be obtained easily. The methods have been applied to obtain the values of the constant K under different experimental conditions. Under optimized conditions the K constant is temperature dependent and non-arrhenian behaviour was observed.
Química Analítica, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, San Luis, Argentina.
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Acosta
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Linares
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Olsina
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Martínez
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Gomez
D002021:Buffers; D002626:Chemistry, Pharmaceutical; D004121:Dimethyl Sulfoxide; D019075:Electrophoresis, Capillary; D006863:Hydrogen-Ion Concentration; D007213:Indomethacin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D017711:Nonlinear Dynamics; D012997:Solvents; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry*
D002021:Buffers; D012997:Solvents; D047392:beta-Cyclodextrins; C031215:betadex; D007213:Indomethacin; D004121:Dimethyl Sulfoxide