Determination of barium, calcium, iron, potassium, magnesium and sodium in high purity niobium pentoxide by flame atomic absorption spectrometry

Abstract

A trace analysis method for niobium pentoxide by flame atomic absorption spectrometry was developed. Determination of 10–400 µg g^–1 of Ba, 1–80 µg g^–1 of Ca, 4–400 µg g^–1 of Fe, 0.5–40 µg g^–1 of Mg (in a dinitrogen oxide-acetylene flame), 0.5–40 µg g^–1 of K (in an air-hydrogen flame) and 0.3–40 µg g^–1 of Na (in an air-acetylene flame) were carried out without matrix separation. The sample was decomposed with a HNO₃-HF mixture using a bomb technique. Hydrogen peroxide was added to transform niobium into the peroxide complex to prevent any hydrolysis subsequent to the binding of the fluoride ion by H₃BO₃. Solutions containing 0.4%V/V HNO₃, 4%V/V HF, 2%V/V H₂O₂, 2%m/V H₃BO₃ and Nb as 2%m/V Nb₂O₅ were studied. The calibration graph method was used. Matrix interferences were overcome by preparing two separate sets of standards for the blank and the sample solutions (containing niobium). Ionisation interferences were suppressed by 0.1% CsCl. Background correction was also found to be necessary.