Two novel zeolitic imidazolate frameworks (ZIFs) as sorbents for solid-phase extraction (SPE) of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples

Abstract

In this work, two novel zeolitic imidazolate framework (ZIF) materials, ZIF-7 and ZIF-11, were firstly introduced as solid-phase extraction (SPE) sorbents for PAHs efficient extraction and highly sensitive analysis in environmental water samples with high performance liquid chromatography (HPLC) coupled with fluorescence detection. ZIF-7 and ZIF-11 were successfully synthesized and characterized with SEM, FTIR, XRD and water contact angels, exhibiting unique and excellent stability, spatial structure and chemical composition, promising for environmental PAHs efficient enrichment through hydrophobic, π–π and π-complexation interactions. The topology effect on PAHs extraction was compared between ZIF-7 and ZIF-11, considering they have the same composition in metal ion (Zn²⁺) and organic linker, but differing spatial structures: ZIF-7 has a cubic structure, while ZIF-11 is a rhombic dodecahedron. At last, ZIF-11 with markedly better extraction efficiencies was selected for subsequent analysis. Under optimum extraction conditions such as sample volume, extraction time, desorption conditions, volume of organic modifier and salt concentration, a robust and highly efficient method based on ZIF-11 as a novel SPE sorbent has been successfully developed for environmental PAHs analysis. Satisfactory precision and accuracy ranging from 1–2.4 × 10³ ng L⁻¹ as well as ultrasensitive detection limits of 0.08–1.6 ng L⁻¹ have been successfully achieved. Moreover, ZIF-11 extraction also exhibited high recoveries of 82.4–112.7% with relative standard deviations (RSDs) being less than 9% for PAHs in the environmental water samples. Therefore, our novel, convenient and efficient extraction method based on ZIF-11 as a sorbent is promising for applications in future trace-level environmental PAHs analyses.