Indirect voltammetric determination of lanthanides in the presence of mordant red 19

Abstract

AbstractComplexes of lanthanide with Mordant Red 19 (MR19) are shown to be adsorbed and can be electrochemically reduced at mercury electrodes at a more negative potential than where MR19 is reduced. Based on these properties, an analytical application for the determination of lanthanides is demonstrated by linear sweep voltammetry (LSV) and by highly sensitive adsorptive stripping voltammetry (AdSV). By applying AdSV, the detection limit of several lanthanides is about 5.0 × 10−10 M with an accumulation time of 5 min and the linear response range is from 5.0 × 10−8 M to 1.0 × 10−6 M. A typical relative standard deviation is found to be 5.2% at the 5.0 × 10−8 M level. The results from LSV show that the difference in peak potentials (δEp) between complex and MR19 increases when the atomic number of lanthanide ion is increased. Because the smallest δEp due to the presence of La3+ is still large enough to distinguish the complex peak from dye peak, it is possible to recognize all members of lanthanide ions selectively with MR19, regardless of whether they are light or heavy ones. It is also possible to perform simultaneous analysis for some mixtures. In addition, the range of lanthanide concentration, for which quantitative analysis is valid, becomes wider as a result of using LSV as well as AdSV.