Mic. Cantagallo et al., DEVELOPMENT OF A CHRONOCOULOMETRIC METHOD FOR THE DETERMINATION OF URANIUM AT TRACE LEVELS BY USING THE CATALYTIC NITRATE REDUCTION, Electroanalysis, 6(11-12), 1994, pp. 1107-1114
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.