Spectrophotometric Determination of the Sum of Rare Earth Elements by Flow-Injection on-Line Preconcentration With a Novel Aminophosphonic–carboxylic Acid Resin

A highly sensitive, selective and accurate spectrophotometric method for the microcolumn on-line preconcentration and determination of the sum of rare earth elements (REEs) was developed. REEs were preconcentrated and separated from matrices by being adsorbed at pH 5.0 on a microcolumn packed with a novel aminophosphonic–carboxylic acid resin (APCR). The adsorbed analytes were desorbed with 1.0 mol L−1 HCl and reacted with Arsenazo III in chloroacetate buffer in a reactor coil for the spectrophotometric detection at 649 nm. The calibration graph was linear up to 1.0 µg mL−1 La3+. The detection limit of 4.0 ng mL−1 was achieved with a sample loading flow rate of 2.0 mL min−1 and a sample loading time of 1.0 min. The RSD was less than 4% for 0.20 µg mL−1 La3+. The proposed method was successfully applied to the determination of the sum of REEs in a geological sample and an aluminum alloy sample.