Magnetic Dispersive Solid Phase Extraction of Cu (II) as 1- (2-pyridylazo)-2-naphthol Chelates on Fe3O4@XAD-16

A novel deep eutectic solvent modified magnetic covalent organic framework for the selective separation and determination of trace copper ion in medicinal plants and environmental samples

BACKGROUND

Pretreatment techniques should be introduced before metal ion determination because there is very low content of heavy metals in Chinese medicinal plants and environmental samples. Magnetic dispersive micro solid phase extraction (MDMSPE) has been widely used for the separation and adsorption of heavy metal pollutants in medicinal plants and environmental samples. However, the majority of MDMSPE adsorbents have certain drawbacks, including low selectivity, poor anti-interference ability, and small adsorption capacity. Therefore, modifying currently available adsorption materials has gained attention in research.

RESULTS

In this study, a novel adsorbent MCOF-DES based on a magnetic covalent organic framework (MCOF) modified by a new deep eutectic solvent (DES) was synthesized for the first time and used as an adsorbent of MDMSPE. The MDMSPE was combined with inductively coupled plasma optical emission spectrometry (ICP-OES) for selective separation, enrichment, and accurate determination of trace copper ion (Cu2+) in medicinal plants and environmental samples. Various characterization results show the successful preparation of new MCOF-DES. Under the optimal conditions, the enrichment factor (EF) of Cu2+ was 30, the limit of detection (LOD) was 0.16 μg L-1, and the limit of quantitation (LOQ) was 0.54 μg L-1. The results for the determination of Cu2+ were highly consistent with those of inductively coupled plasma mass spectrometry (ICP-MS), which verified the accuracy and reliability of the method.

SIGNIFICANCE

The established method based on a new adsorption material MCOF-DES has achieved the selective separation and determination of trace Cu2+ in medicinal and edible homologous medicinal materials (Phyllanthus emblica Linn.) and environmental samples (soil and water), which provides a promising, selective, and sensitive approach for the determination of trace Cu2+ in other real samples.

Ionic liquid-immobilized silica gel as a new sorbent for solid-phase extraction of heavy metal ions in water samples

In the current study, we have developed a solid-phase extraction (SPE) method with novel C18-alkylimidazolium ionic liquid immobilized silica (SiO₂–(CH₂)₃–Im–C₁₈) for the preconcentration of trace heavy metals from aqueous samples as a prior step to their determination by inductively coupled plasma mass spectrometry (ICPMS). The material was characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Energy-Dispersive X-ray Spectroscopy (EDS), and Brunauer–Emmett–Teller (BET) analysis. A mini-column packed with SiO₂–(CH₂)₃–Im–C₁₈ sorbent was used for the extraction of the metal ions complexed with 1-(2-pyridylazo)-2-naphthol (PAN) from the water sample. The effects of pH, PAN concentration, length of the alkyl chain of the ionic liquid, eluent concentration, eluent volume, and breakthrough volume have been investigated. The SiO₂–(CH₂)₃–Im–C₁₈ allows the isolation and preconcentration of the heavy metal ions with enrichment factors of 150, 60, 80, 80, and 150 for Cr³⁺, Ni²⁺, Cu²⁺, Cd²⁺, and Pb²⁺, respectively. The limits of detection (LODs) for Cr³⁺, Ni²⁺, Cu²⁺, Cd²⁺, and Pb²⁺ were 0.724, 11.329, 4.571, 0.112, and 0.819 μg L⁻¹, respectively with the relative standard deviation (RSD) in the range of 0.941–1.351%.

Novel C18-alkylimidazolium ionic liquid immobilized silica (SiO₂–(CH₂)₃–Im–C₁₈) was synthesized through a four-step procedure. It showed high efficiency for the separation/preconcentration of trace heavy metal ions from aqueous samples.