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 (Zn(2+)) 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 × 10(3) 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.

Development of high internal phase emulsion polymeric monoliths for highly efficient enrichment of trace polycyclic aromatic hydrocarbons from large-volume water samples

“…Of those sample preparation methods, SPE was preferred by many researchers in the extraction and enrichment of trace PAHs. So far, many different SPE sorbents, such as metal-organic frameworks [31,32,36], molecularly imprinted polymers [33], multiwalled carbon nanotubes (MWCNTs) [40] and carbon coated Fe 3 O 4 nanoparticles [41], have been used to enrich PAHs from complex aqueous samples, and exhibited good enrichment performance. However, to the best of our knowledge, monolithic polyHIPEs columns for extraction and enrichment of trace PAHs from complex samples have not yet been reported.…”

“…Therefore, PAHs have been listed as priority pollutants by the United States Environmental Protection Agency (US-EPA) and European Union (EU), and many studies have already been conducted to determine the amount of PAHs in water, food, soil and other samples, and many excellent review papers related to PAHs analysis have been published over the years [27][28][29]. Since PAHs exist in the environment, especially water media in the trace levels (their maximum contaminant levels should not exceed 200 ng/L according to the US-EPA regulations) [30], a sensitive method is desired to preconcentrate these analytes more efficiently prior to detection, and at present several proconcentration methods, including solid phase extraction (SPE), stir bar sorptive extraction (SBSE), solid phase microextraction (SPME) and liquid-liquid microextraction (LLME), have been developed and applied to enrichment of PAHs, especially these listed sixteen PAHs, from water samples [31][32][33][34][35][36][37][38][39][40][41]. Of those sample preparation methods, SPE was preferred by many researchers in the extraction and enrichment of trace PAHs.…”

Recent applications of metal–organic frameworks in sample pretreatment

“…ZIF‐11 was successfully applied in D‐μ‐SPE by Hu et al. to extract PAHs with LODs of 0.08–1.6 ng/L. Three kinds of MOFs (MIL‐100, MIL‐101, and MIL‐53) were utilized by Gu et al.…”

Magnetite nanoparticles surface-modified with a zinc(II)-carboxylate Schiff base ligand as a sorbent for solid-phase extraction of organochlorine pesticides from seawater

“…In addition, it has been proven that Zn(II) ion can form π-complexation with unsaturated carbon bonds [19]. Therefore, the presence of zinc ions in framework of sorbent, can facilitate extraction of aromatic analytes through π-complexation interaction [20]. MNPs coated with fatty acid have been used as sorbent materials for the enrichment of organochlorine pesticides in water samples [21].…”