Analytical Sciences

Abstract − Analytical Sciences, 18(4), 427 (2002).

Differential Pulse PolarographicDetermination of Uranium(VI) in Complex Materials after Adsorption of ItsTrifluoroethylxanthate Cetyltrimethylammonium Ion-Associated Complex onNaphthalene Adsorbent
Bal K. PURI,* Atamjyot,* Keemti LAL,** and HimanshuBANSAL***
*Department of Chemistry, IndianInstitute of Technology, Hauz Khas, New Delhi-110016, India
**Departmentof Chemistry, D. N. College, Meerut (U.P.), India
***Department ofChemistry, Vishveshwarya Institute of Engineering & Technology, G. T. Road,Dadri (U.P.), India
Uranium(VI) is adsorbed as a uraniumtrifluoroethylxanthate (TFEX)-cetyltrimethylammonium (CTMA) ion-paircomplex on microcrystalline naphthalene quantitatively in the pH range 4.2- 7.0. Without cetyltrimethylammonium as the counter ion, the adsorptionis hardly 70%. The metal has been desorbed with HCl and determined with adifferential pulse polarograph. Uranium can alternatively bequantitatively adsorbed on TFEX-CTMA-naphthalene adsorbent packed in acolumn at a flow rate of 1 - 5 ml/min and determined similarly. Awell-defined peak has been obtained in this medium at -0.20 V versusa saturated calomel electrode. Cyclic voltammetry, differential pulsepolarography and D.C. polarography studies indicate that uranium has beenreduced irreversibly under these conditions. The detection limit is 0.30ug/ml at the minimum instrumental settings (signal-to-noise ratio of 2)(with a preconcentration factor of 10, the detection limit would be 30ng/ml for uranium when the volume in the cell is 15 ml). However if thevolume in the cell is 5 ml, it would have been 10 ng/ml with apreconcentration factor of 30. Linearity is maintained in a concentrationrange of 0.5 - 19.0 ug/ml (2.1 - 79.83 x 10-9 M) with acorrelation factor of 0.9994 and a relative standard deviation of ±1.1% (in this case 7.5 ug may be concentrated from 150 ml of the aqueoussample where its concentration is as low as 50 ng/ml). Various parameters,such as the effect of the pH, volume of the aqueous phase, flow rate andthe interference of a large number of metal ions and anions on thedetermination of uranium, have been studied in detail to optimize theconditions for its trace determination in various complex materials, likealloys, coal fly ash, biological, synthetic, and waste-watersamples.