Selective extraction and preconcentration of trace lead(ii) in medicinal plant-based ionic liquid hollow fiber liquid phase microextraction system using dicyclohexyl-18-crown-6 as membrane carrier

Abstract

A novel three-phase ionic liquid hollow fiber liquid phase microextraction (IL-HF-LPME) system was used for the selective extraction and preconcentration of Pb(II) from medicinal plants. Green solvent ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF₆) containing dicyclohexyl-18-crown-6 (DCH18C6) was used as membrane phase immobilized in the hollow fiber pores. Ethylene diamine tetraacetic acid was used as stripping agent that can form water-soluble complex with Pb(II) in the lumen of the hollow fiber. After extraction, the acceptor solution was directly injected into a graphite furnace atomic absorption spectrometer for analysis. A Box–Behnken design was used to study the influence of DCH18C6 concentration, extraction time and pH on the extraction efficiency. Under the optimized conditions, an enrichment factor of 199 and a limit of detection of 0.008 ng mL⁻¹ were obtained. The calibration curve was linear in the range of 0.05–0.5 ng mL⁻¹ (R = 0.999). Moreover, the obtained results show that DCH18C6 can selectively and efficiently transport Pb(II) from the aqueous phase containing different concentrations of heavy metal ions (Cd²⁺, Co²⁺, Cu²⁺, Ni²⁺, Fe²⁺, Zn²⁺). The proposed method was successfully applied to determination of Pb(II) in medicinal plants with satisfactory recoveries in the range of 94–102%.