Synthesis and modification of MIL-101-NH2-based metal organic frameworks for preparation of SPME fibers using sol-gel methodology

Abstract

Implementation of metal-organic frameworks (MOFs) in the separation science is attractive for many researchers, nowadays. In this study, three MOFs were synthesized and employed as extractive coating fibers. The MIL-101-NH₂-based coatings were implemented in immersed solid phase microextraction (ISPME) of organophosphorus pesticides (OPPs) from real-life samples. The three different kinds of fiber coatings included MIL-101-NH₂ and its acyl and ethyl modified structures as particles and 3-aminopropyl triethoxysilane (APTES) sol-gel precursor as binder. Each single MOF was coated on a stainless steel substrate via sol-gel technique. The uniform and tunable pore structure, high surface area, and capability to functionalization of MIL-101-NH₂, make it susceptible for isolation of a wide range of analytes from small to large molecules. Extraction performance of the synthesized fiber coatings with different functionalities was examined on some model OPPs, followed by gas chromatography-mass spectrometry (GC–MS). The highest extraction efficiency was achieved by the acyl-modified (MIL-101-NHCOCH₃) fiber coating. The effects of various parameters affecting the extraction and desorption efficiency such as desorption time, desorption temperature, ionic strength, stirring rate, extraction time and temperature for the selected fiber were investigated and optimized. All the synthesized fiber coatings showed sufficient affinity while the acyl modified extractive phase was found to be very sensitive for determination of OPPs with reliable figures of merit such as acceptable linear dynamic ranges (1–1000 & 5–1000 ng.kg⁻¹, here two linear dynamic ranges (LDR) are reported due to the variation of LDR ranges from one analyte to another), low limits of detection (0.2–1 ng.kg⁻¹), suitable intra–day (RSD% <13%) and inter–day relative standard deviation (RSD% <15%).