Retention behaviour of uranium and thorium and their determination on an amide-coated reverse phase column by HPLC

The retention behaviour of uranium and thorium was investigated using a reverse phase column modified with N,N-dialkyl amides, such as dihexyl hexanamide (DHHA), dibutyl hexanamide (DBHA), diisooctyl butanamide (DiOBA), or dioctyl hexanamide (DOHA). alpha-Hydroxy isobutyric acid (HIBA) is employed as the mobile phase. The retention behaviour was compared with that observed on the uncoated C-18 support. The retention was also investigated on C-18 modified with another neutral extractant, trihexyl phosphate (THP), uncoated C-8 support, and amide-coated C-8 support, to understand the retention mechanism. Uranium and thorium can be separated from each other with good peak profiles and baseline resolution. Rapid separations could be achieved by proper choice of column coating. On the basis of these studies, a HPLC technique has been developed for the separation and determination of uranium in the presence of large amounts of thorium, i.e., uranium can be estimated accurately in the presence of about 1000 times of thorium.