SPECTROPHOTOMETRIC DETERMINATION OF THE SUM OF RARE EARTH ELEMENTS BY FLOW-INJECTION ON-LINE PRECONCENTRATION WITH A NOVEL AMINOPHOSPHONIC–CARBOXYLIC ACID RESIN

ABSTRACT

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.

Keywords:

• Spectrophotometry
• Determination
• Rare-earth elements
• On-line preconcentration
• Aminophosphonic–carboxylic acid resin

ACKNOWLEDGMENTS

The financial support of the University Key Teacher by the Ministry of Education (No. 65, 2000) and the Foundation of Doctoral Programs of the Ministry of Education (No. 21) of China were gratefully acknowledged.