Selective determination of niobium in natural waters at the low ng L− 1 level by differential pulse cathodic stripping voltammetry in the presence of pyrogallol red

Abstract

A completely selective method for electrochemical determination of very low concentrations (ngL−1) of niobium is presented. The method relies on the cathodic reduction of the pyrogallol red‑niobium complex at pH3. Virtually no sample preparation (apart from cation exchange) is required. The method is both free from interferences (particularly from Ta) and affordable. Time consuming preconcentration and separation procedures as well as the use of hydrofluoric acid, fluorides or problematic solvents are avoided. The applicability of the method is illustrated through analysis of mineral waters containing niobium concentrations ranging from 1 to several hundred ngL−1.