Solid-phase extraction based on polyethyleneimine-modified eggshell membrane coupled with FAAS for the selective determination of trace copper(ii) ions in environmental and food samples

Abstract

Polyethyleneimine (PEI) can selectively capture trace-level free copper ions (Cu²⁺), from which the true toxic effects of copper originate. Thus, PEI-functionalized eggshell membrane (ESM) may serve as a green, economical, easily available, and selective solid phase extraction (SPE) adsorbent material for Cu²⁺ enrichment. In this paper, the potential of the PEI-functionalized ESM (PEI–ESM) as a biosorbent for the selective solid phase extraction and preconcentration of trace Cu²⁺ in environmental water samples and food samples in combination with flame atomic absorption spectrometry (FAAS) was investigated. After modification, the dynamic uptake capacity of PEI–ESM increased by about 20-fold compared with ESM. Various factors affecting Cu²⁺ extraction by SPE were investigated. Under the optimal conditions, Cu²⁺ could be easily extracted by the PEI–ESM packed cartridge. The favorable limit of detection (LOD) for Cu(II) was 0.15 μg L⁻¹ with an enrichment factor of 100, and the relative standard deviation (RSD) was 2.0% for 50 μg L⁻¹ Cu(II) (n = 11). The reproducibility among columns was satisfactory (RSD among the columns is less than 5%). Stability testing demonstrated that the PEI–ESM maintained over 92.0% recovery for Cu(II) even after a run of 45 adsorption and desorption cycles, showing its operational stability. The proposed method has been applied successfully to the analysis of copper in environmental water samples and food samples, which demonstrated that PEI–ESM could be an excellent SPE adsorbent for copper pretreatment and enrichment from real water samples and food samples.