Square Wave Polarographic Determination of Cationic Surfactants with Cd(Ⅱ) as Indicative Ion

It was found that by the addition of a definite amount of Cd(Ⅱ) ion,the non-electroactive cationic surfactant,dodecyl dimethyl benzyl ammonium chloride or designated as 1227,in microamounts,was determined by square wave polarography.Value of peak current of Cd(Ⅱ) ion (called the indicative ion) increases with the increase of concentration of 1227 in a definite range.Mechanism of the reaction at the working electrode was somewhat complex,composing the fast adsorption of the cationic CdCl+ ion and slow adsorption of the cation of 1227,R+ on the cathode,leading to increase of peak current in the former case and decrease of peak current in the latter case.Mathematical model of reduction peak current of Cd(Ⅱ) ion in the presence of 1227 was obtained by simulation with the program Origin 7.0.And also by the NLSF simulation with Origin 7.0,Values of adsorption constants and affecting factors of the cations CdCl+ and R+ were found,and values of peak current of the complex adsorption process were calculated quantitatively.Value of RSD (n=5) of this method was found to be 2.2%,and result of recovery test obtained by standard addition method were 96.8%.