ANALYSIS OF THE ELECTROSTATIC POTENTIAL DIFFERENCE IN AQUEOUS POLYMER2-PHASE SYSTEMS

Experimental partition coefficients of two ionic dyes in two-phase sys tems water+poly(ethylene glycol) 3000+dextran 500000 containing variou s salts are presented. Based on these data unambiguous information on the electrostatic potential differences induced by the salts is obtain ed. To achieve this goal the model proposed by Albertsson (1986) is ap plied to systems containing mixed salts to account for an ionic impuri ty present in the polymer samples. With both dyes the value of Delta p hi(Na2SO4)-Delta phi(NaCl)=4.7 mV at salt concentrations up to 50 mmol kg(-1) is obtained. Also the partition coefficients of the salts are predicted in agreement with the experiment. These results indicate tha t up to a salt concentration of approximately 50 mmol kg(-1) the Alber tsson model can be applied. Above this concentration limit, the basic two-phase system is altered and the model predictions are severely in error.