Determination of trace phosphorus in zirconium-niobium alloy and Zircaloy by UV-vis spectrophotometry

A spectrophotometric method has been developed for the determination of traces of phosphorus in zirconium based alloys (Zr-2.5Nb and Zircaloy). It is achieved by selective fluoride complexation controlled by boric acid. The samples were dissolved in HF and fluoro-complexes of the matrices were formed by maintaining the concentration of HF while the excess HF was controlled by boric acid. After the formation of phosphomolybdate, extracted into n-butyl acetate, ion-associated with crystal violet and the absorbance was measured at 582 nm. The results obtained by this procedure were in close agreement with the certified reference material (CRM) values and further these values were compared with the values determined by Glow Discharge-Quadrupole Mass Spectrometry (GD-QMS). The potential interferences like fluoride, silicon, arsenic(V), niobium, titanium, tantalum, etc., were tolerable to large level. LOD (3 s) was found to be 0.055 mg kg(-1) with a precision (R.S.D.) of 2-3% and molar absorptivity was 2.7x10(5) L mol(-1) cm(-1).