DEVELOPMENT OF A CHRONOCOULOMETRIC METHOD FOR THE DETERMINATION OF URANIUM AT TRACE LEVELS BY USING THE CATALYTIC NITRATE REDUCTION

The electroanalytical determination of uranium at trace levels was stu died with the purpose of improving the sensitivity of the uranium-cata lyzed reduction in the presence of nitrate on mercury electrode. Exami nation of the current dependence on time (chronoamperometry) revealed the advantage of measuring the current later and for a longer time int erval than usual in pulse polarography. The uranium/nitrate system is particularly favorable in this sense because an intensification of the catalytic current with time is observed. The best signal-to-noise rat io was achieved using the technique of chronocoulometry. In this chron ocoulometric catalytic determination (CCCD), analytical information wa s gathered, calculating the slope of the charge versus time curve duri ng the period of 10 to 20 seconds after the application of the potenti al pulse and correcting it for the residual slope before the pulse. To establish the new analytical procedure, the effects of electrolyte co mposition, potential program, integration time, and blank correction w ere examined. A detection limit of 3 x 10(-10) M was attained, a power of ten lower than the sensitivity reported for the same catalytic det ermination by differential pulse polarography. An exploratory study of the combination of this procedure with preconcentration of uranium on the electrode allowed reduction of the detection limit by an addition al order of magnitude.