Preconcentration of f-elements from aqueous solution utilizing a modified carbon paste electrode.

An evaluation using paraffin oil based, Acheson 38 carbon paste electrodes modified with α-hydroxyisobutyric acid (HIBA) to preconcentrate f-elements cathodically is described. The modified paste was made by directly mixing solid HIBA into the carbon paste. A chemically reversible cyclic voltammogram for HIBA was observed on this modified carbon paste, which was found to be a non-Nerstian, single electron transfer process. Lanthanides (less promethium) were found to accumulate onto the electrode surface during a 30 s electrodeposition step at -0.4 V vs Ag/AgCl from 0.1 M LiCl. The elements were then stripped off into a 2% HNO(3) solution by an oxidative step at +0.8 V vs Ag/AgCl; quantitative removal from the electrode was confirmed by ICPMS. Ultratrace solutions with initial concentrations down to 5 parts per quadrillion (ppq) were preconcentrated in 5 min above our instrumental limit of detection (LOD) of around 1 ppt for lanthanides.