Spectrophotometric Determination of Lanthanum(Ⅲ) with Arsenazc Ⅲ as Color Reagent and Sensitized by the Synergic Action of Triton X-100 and β-Cyclodextrin

A method of spectrophotometric determination of lanthanum(Ⅲ) was proposed.Arsenazo Ⅲ was used as color reagent and sensitized by the synergic action of Triton X-100 and β-CD.The color reaction was carried out in a solution containing 0.20 mL of 0.02 mol·L-1 HCl,4.0 mL of 0.5% Triton X-100 solution,2.0 mL of 0.01 mol·L-1 β-cyclodextrin,and 2.0 mL of 500.0 mg·L-1 arsenazo Ⅲ solution in a total volume of 50 mL.Twenty five min.were required for the completion of the color reaction.Beer′s law was kept in the range of 0.20-100.0 mg· L-1 when measured at the absorption maximum of 652 nm.Detection limit (3S/N) found were 0.20 mg·L-1 respectively.The proposed method was used in the determination of lanthanum(Ⅲ) ion in 3 simulated ore samples,with values of RSD′s (n=5) in the range of 2.1%-3.1%.