Mathematical representation of electrophoretic mobility in ternary solvent electrolyte systems

Abstract

Electrophoretic mobilities of salmeterol and phenylpropanolamine in capillary zone electrophoresis were determined using acetate buffer in mixed solvents containing different concentrations of water, methanol and acetonitrile. Maximum electrophoretic mobilities for salmeterol and phenylpropanolamine were observed with water-methanol-acetonitrile ratios of 5:50:45 v/v and 3:60:37 v/v, respectively, and minimum mobilities of both compounds occurred in methanol-acetonitrile ratio of 30:70 v/v. The generated experimental data have been used to evaluate a mathematical model to compute the electrophoretic mobility of the analytes in a ternary solvent electrolyte system. The proposed model is: ln μm =ƒ1 ln μ1+ƒ2 ln μ2+k ƒ3+M1ƒ1 ƒ2+M2 ƒ1ƒ3+M3 ƒ2ƒ3+M4 ƒ1ƒ²1+M5 ƒ²2ƒ3+M6ƒ²2ƒ3+M7ƒ1ƒ2ƒ3. Where μ is the electrophoretic mobility, subscripts m,1, 2 and 3 refer to mixed solvent and solvents 1-3, respectively, f is the volume fraction of the solvent in the mixed solvent system and M1-M7 and K are the model constants calculated by a least squares analysis. The generated experimental data fitted to the model and the back-calculated mobilities were employed to compute the average percentage deviation (APD) as an accuracy criterion. The obtained APD for salmeterol and phenylpropanolamine are 3.10 and 2.21%, respectively and the low APD values indicate that the model is able to calculate the mobilities within an acceptable error range.