A novel CPE procedure by oil-in-water microemulsion for preconcentrating and analyzing thorium and uranium

A novel cloud point extraction (CPE) procedure was developed to preenrich Th4+ and UO22+ by oil-in-water (O/W) microemulsion. Coupling CPE to ICP-MS, the separation and analysis were achieved at a trace level, in which the low detection limits were 0.019 and 0.042 ng mL(-1) for Th(IV) and U(VI), respectively. N,N '-diethyl-N,N '-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), as an extremely hydrophobic extractant, was failed to dissolve in single or mixed micelles, but was successfully solubilized to CPE system owing to O/W microemulsion. The extraction efficiency and selectivity for Th4+ and UO22+ were excellent under acidic condition of 1.0 mol L-1 HNO3, and the recovery of ultra-trace Th4+ and UO22+ was almost 100% even at the presence of large amounts of lanthanides, exhibiting high tolerance limits for lanthanides. The solubilization, extraction and coordination behaviours were studied systematically via DLS, UV-vis, H-1 NMR and FT-IR. Moreover, the solubilization of N,N '-dioctyl-N,N '-dioctyl-2,9-diamide-1,10-phenanthroline (Oct-Oct-DAPhen) and efficient extraction for UO22+ were also realized by O/W microemulsion, which further proved the feasibility of the method.

Automated summary

A novel cloud point extraction procedure using oil-in-water microemulsion was developed for preenrichment and separation of Th4+ and UO22+ at trace level. The method showed excellent efficiency, selectivity, and tolerance limits for lanthanides.