Quantification of rare earth elements using cloud point extraction with diglycolamide and ICP-MS for environmental analysis

Abstract

This article describes the development of a procedure for the bulk separation and determination of rare earth elements in soils by combining alkaline fusion, cloud point extraction, and inorganic mass spectrometry. The proposed cloud point extraction method uses a diglycolamide derivative as the chelating agent, which has a well-established affinity for rare earth elements. The method integrates bromine shielding to achieve efficient phase separation at highly acidic pH values. The methodology led to very low detection limits (0.2 to 30 ng L⁻¹), quantitative extraction (>97%) for soils, and a high preconcentration factor (up to 140). Decontamination factors were assessed for the most abundant elements, including trivalent ions such as Al³⁺ and Fe³⁺. A reduction in concentration of up to 180-fold was measured for some elements. Quantitative recoveries for most rare earth elements in highly acidic conditions were achieved and validated using sediment reference material (NIST-2709a). There was excellent agreement between the expected and measured concentrations for all 16 rare earth elements evaluated. The superior analytical figures of merit enabled rare earth elements determination at ultra-trace levels in environmental samples.