A.c. conductivity measurements in isotachophoresis

Isotachopherograms are measured by an a.c. cond. method, with driving current values of 30-150 mA. The detection electrode system, and resistance measurement circuitry are described. A combination of current source (0.81 kHz) and voltmeter was used. The thermocouple was close to the Pt electrodes. The inner and outer diam. of the capillary tube were 0.45 and 0.7 mm, resp. Both the capillary tube and the anode compartment were filled with a soln. of 0.01M histidine and 0.01M histidine.2HCl. The cathode compartment was filled with 0.01M glutamic acid. The calcd. and measured isotachopherograms, of resistance change vs. time (0-25 sec) are in satisfactory agreement. A model of the current distribution in the electrolyte near the electrodes was used for the calcd. curve. The boundary passage takes .apprx.5 sec; the measured boundary width is .apprx.1 mm. The resoln. of the cond. method is similar to that of the uv method (L. Arlinger and R. Routs, 1970. [on SciFinder (R)]