Fluorometric determination of niobium and tantalum with hydrazone reagents

As fluorometric reagents for niobium and tantalum and several heavy metal i ons, three derivatives of hydrazone { 2-pyridinecarboxaldehydepicolinoylhyd razone(hyd .H), 2-acetylpyridinepicolinoylhydrazone (hyd . CH3), 2-benzoylp yridinepicolinoylhydrazone (hyd .C6H5)} were synthesized. The hyd .H was a specific and excellent fluorometric reagent for niobium(V), because the rea gent did not react with tantalum(V). However the hyd . CH3 was effective fo r the fluorometric determination of the total amount of niobium(V) and tant alum(V) in the presence of tartaric acid(4 mg/25 cm(3)). Further, the fluor ometric intensity of hyd . CH3-Nb(V) and hyd . CH3- Ta(V) complexes showed an additive property. Because fractional determinations of niobium(V) and t antalum(V) are possible by these reagents, they were used for the rapid and accurate determination of niobium(V) and tantalum(V) in minerals. The rela tive standard deviation (n = 5) of fluorometric measurements was less than 3.7% at 2 mug of niobium(V) for a tantalum determination with hyd . CH3, an d 1.9% at 5 mug of niobium(V) for a niobium determination with hyd .H. Two minerals were analyzed. Fergusonite contained 19.8% of Nb2O5 and 5.66% of T a2O5, and manganotantalite contained 5.12% of Nb2O5 and 50.3% of Ta2O5.