Flow injection on-line solid phase extraction coupled with inductively coupled plasma mass spectrometry for determination of (Ultra)trace rare earth elements in environmental materials using maleic acid grafted polytetrafluoroethylene fibers as sorbent

A new sorbent, maleic acid grafted polytetrafluoroethylene fiber (MA-PTFE), was prepared and evaluated for on-line solid-phase extraction coupled with inductively coupled plasma mass spectrometry (ICP-MS) for fast, selective, and sensitive determination of (ultra)trace rare earth elements (REEs) in environmental samples. The REEs in aqueous samples at pH = 3.0 were selectively extracted onto a microcolumn packed with the MA-PTFE fiber, and the adsorbed REEs were subsequently eluted on-line with 0.9 mol l⁻¹ HNO₃ for ICP-MS determination. The new sorbent extraction system allows effective preconcentration and separation of the REEs from the major matrix constituents of alkali and alkali earth elements, particularly their separation from barium that produces considerable isobaric interferences of ¹³⁴Ba¹⁶O¹H⁺, ¹³⁵Ba¹⁶O⁺, ¹³⁶Ba¹⁶O¹H⁺, and ¹³⁷Ba¹⁶O⁺ on ¹⁵¹Eu⁺ and ¹⁵³Eu⁺. With the use of a sample loading flow rate of 7.4 ml min⁻¹ for 120 s preconcentration, enhancement factors of 69–97 and detection limits (3s) of 1–20 pg l⁻¹ were achieved at a sample throughput of 22 samples h⁻¹. The precision (RSD) for 16 replicate determinations of 50 ng l⁻¹ of REEs was 0.5–1.1%. The developed method was successfully applied to the determination of (ultra)trace REEs in sediment, soil, and seawater samples.