Simple and fast voltammetric procedure of U(Ⅵ) determination in the presence of high concentrations of surface active substances

摘要

In this work, a simple and fast procedure for elimination of interfering surface active substances and for U(Ⅵ) adsorptive stripping voltammetric determination was developed. The adsorption in the form of U(Ⅵ)-cupferron complexes was performed, because as it was proved before, U(Ⅵ) forms with cupferron stable complexes, which were employed in voltammetric procedures. The procedure is based on two steps: the first is an adsorption of surface active substances onto an Amberlite XAD-16 or XAD-7 resin and the second is a voltammetric determination of U(Ⅵ) with a pulsed potential of accumulation alternate -0.65-0.3 V with the frequency of 0.5 Hz and then the differential pulse voltammogram was recorded, whereas the potential was scanned from -0.65 to -1.2 V. The detection limit estimated from three times the standard deviation for a low U(Ⅵ) concentrations was equal to 1.7 × 10~(-10) mol L~(-1) (7.2 × 10~(-8) g L~(-1)). The linear range of U(Ⅵ) was observed over the concentration range from 5.0 × 10~(-10) mol L~(-1) (2.1 × 10~(-7) g L~(-1)) to 2.0 × 10~(-8) mol L~(-1) (8.5 × 10~(-6) g L~(-1)) for an accumulation time of 60 s. The influence of different kinds of surfactants, such as non-ionic, cationic and anionic on the uranium voltammetric signal was studied. The results confirm the possibility of U(Ⅵ) determination in water samples containing high concentrations of surface active substances even up to 50 mg L~(-1).