Determination of micro strontium in barium octahydrate by spectrophotometry with arsenazo III

The content of strontium in barium octahydrate was determined by spectrophotometry in HAc-NaAc buffer solution at pH 6.4 with arsenazo III as the coloring agent.In the method,Ba2+ was separated by precipitation with K2CrO4,Ca2+ was masked with EGTA and Fe3+,Al3+ was masked with triethanolamine.The experiments showed that strontium could form a blue complex with arsenazo Ⅲ.The maximal absorption peak of the complex was at 640 nm.Beer's law was obeyed for strontium in the range of 0-3.4 μg/mL with apparent molar absorptivity of e=2.2×104 L·mol-1·cm-1.This method was applied to the determination of micro strontium in barium octahydrate,giving relative standard deviations(RSD) of 0.13 %-0.19 %(n=5).The determination results were in good agreement with those obtained by atomic absorption spectrometry.