Bimodal UVM-7-based periodic mesoporous organosilica containing benzimidazole for thin film microextraction of triazole fungicides in fruiting vegetables prior to gas chromatography-mass spectrometry

Background

Periodic mesoporous organosilicas (PMOs) are a new class of organic-inorganic hybrid materials with high surface area, narrow pore size distribution, high functional group loading, and tunable functional groups. In contrast to other porous organosilicate materials, PMOs show a uniform distribution of organic groups inside their framework walls. They are synthesized by condensing bis-silylated organic precursors around a surfactant template. Their application severely depends on textural features like pore structure, particle size, porosity and surface area. This study focuses on the application of PMOs in trace determination of pesticides, while the structural features of these interesting materials are strongly considered.

Results

Different PMOs with UVM-7 and SBA-15 type mesostructures were synthesized using benzimidazolium salt as the organic modifier. Then the prepared PMOs were employed in thin film microextraction (TFME) composed from Nylon-6 substrate prior to gas chromatography-mass spectrometry (GC-MS) analysis. Afterward, a simple method was adapted for detecting trace amounts of six triazole fungicides in extracts of five commonly consumed fruiting vegetables. The prepared bridged benzimidazolium salt organosilica-based sorbents underwent extensive characterization by FTIR, TEM, SEM, EDX, BET and XRD investigations. After obtaining the extraction results for both PMOs, the best one was implemented as the extractive phase in the further experiments. After optimization, limits of detection and quantification ranged from 0.02 to 0.2 and 0.06–0.7 μg L⁻¹, respectively. The linearity of calibration plots varies at the range of 0.1–500 μg L⁻¹ (R² = 0.996). Relative standard deviations (RSDs) were found to be 3.9–14.1 %. The relative recoveries (85–115 %) show that this approach works appropriately to detect triazole fungicides in real matrixes.

Significance

PMOs framework upon similar structures with azole fungicides provide interaction between sorbent and the desired analytes. For the first time, the superior PMO nanoparticles with high surface area and accessible bimodal pore systems (UVM-7) were evaluated in thin film microextraction of triazole fungicides from 10-fold diluted fruiting vegetable samples. This study proves PMO structure can be engineered by controlling the synthesis condition depending on application requirements. This finding opens a new horizon in preparing structurally specified sorbents for microextraction purposes.