Direct determination of niobium at the low nanogram level in mineral waters and freshwaters

The increasing use of elements such as Nb and Ta in green and information technologies makes it necessary to develop appropriate analytical methods for studying their environmental and ecotoxicological behaviour. This paper describes the first time Nb has been directly identified in mineral and freshwaters, using inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The scant values of Nb concentrations in freshwaters published include many values which are very close, or directly below, the detection limit of the technique used; when low values are reported, the techniques used often include solid phase extraction preconcentration; with the associated difficulty in obtaining low blanks and risk of incomplete resin desorption. We analysed 20 water samples of contrasting characteristics along with certificate reference material SLRS-5. Values detected ranged from 0.3 to 12 ng L-1. No sample was below the detection limit. Our results show that the determination of Nb by ICP-SFMS is possible, although it is not a routine analysis (i.e., it requires excellent blanks and machine response stability). These results are consistent with existing information. Currently, Nb ecotoxicological characteristics and behaviour in environmental compartments are essentially unknown; the possibility of directly determining Nb at these concentrations opens up new avenues for studying this element at meaningful environmental levels.