Determination of traces of uranium in environmental samples using a flow injection system with amperometric catalytic detection

A new method for flow injection analysis (FIA) of traces of uranium by cata lytic amperometric detection in nitrate medium is described. Interfering ox ygen was removed by in-line degassing. A simple adapter was designed to aff ord FIA with batch cells comprising a hanging mercury drop electrode. The c arrier electrolyte consisted of 10 mM LiNO3 and the electrolyte for the sam ples was 10 mM HNO3 + 10mM LiNO3. The method is simple, rapid (up to 60 inj ections/h) and precise (RSD = 1.0% for n = 10 and C-U = 80 nM), presenting a LD of 13 pg of U or 3nM (3 SD). Dissolution of solid samples (rock and so il) was abbreviated by employing a mixture of nitric and hydrofluoric acids in microwave heated closed vessels, followed by liquid-liquid extraction w ith TBP. Analysis of reference materials and intercomparison with other tec hniques gave very favorable results.