ENHANCED STABILITY OF ELECTROCHEMICAL DETECTION WITH SURFACTANT CONTAINING MOBILE PHASES IN LIQUID-CHROMATOGRAPHY AND FLOW-INJECTION ANALYSIS

The use of surfactant containing mobile phases to prevent or reduce the effects of adsorptive fouling of glassy carbon electrodes is reported. Both cationic and anionic surfactants are studied at concentrations above and below the critical micelle concentration. For the oxidative reactions studied here, anionic surfactants have little effect on the fouling problem, likely because of electrostatic attraction of the generated cationic intermediate to surfactant adsorbed on the electrode surface. Cationic surfactants, however, have the desired effect. Two cationic surfactants, cetyltrimethylammonium chloride and n-decylamine were studied with solutes p-nitrophenol, phenylenediamine and chlorpromazine. With these surfactants present in the mobile phase there was generally no loss of electrochemical response after up to 55 sequential injections. Adsorption of the electroactive specie prior to the electron-transfer process is shown to be a significant cause of poor chromatographic efficiency for some solutes.