UV–Vis spectroscopical and electrochemical detection of La³⁺, Ce⁴⁺ and Nd³⁺ in aqueous media using modified graphite electrodes

This paper shows a comparison and discussion of the detection results, by spectrophotometric and electrochemical methods, for La³⁺, Ce⁴⁺ and Nd³⁺ in aqueous medium. The obtained values of detection and quantification limit of cerium and neodymium by the spectrophotometric method were 1.7E⁻⁵ and 5.5E⁻⁵ M and 0.7 and 2.3 M respectively. However, a lanthanum signal was not detect in a 200–900 nm wavelength range. The cyclic voltammetry electrochemical method was also tested. It employed graphite, modified graphite electrode with Cyclam and modified graphite electrode with Phthalocyanine as working electrode in the electrochemical cell. The lowest values of detection and quantification limit of lanthanum and neodymium 1.6E⁻⁷ and 5.9E⁻⁷ M and 1.7E⁻⁷ and 5.9E⁻⁷ M respectively were obtained with pre-functionalized electrodes at 1.6 V and modified with Phthalocyanine by immersion; indicating that the electrochemical method provides greater sensitivity in the detection and quantification limits than the spectrophotometric method for these species. The feasibility of applying modified graphite as working electrode to detect actinides in an electrochemical method provides a new isotopic characterization technique. This technique would improve efficiency for radioactive compounds management in the aqueous systems of a nuclear reactor, which is considered the fundamental problem in the use of nuclear energy.