Abstract:

The development of high-throughput sample pretreatment methods is essential for the rapid screening and accurate analysis of contaminants in food and environmental matrices. In this study， we established a novel high-throughput sample pretreatment approach for glyphosate using a 96-blade thin-film microextraction （TFME） device. The blade surface was coated with a functionalized metal-organic framework （MOF） as the extractive phase. Specifically， a fluorinated zirconium-based MOF （UiO-66-F₄） was synthesized via a hydrothermal method. Various characterization techniques， including scanning electron microscopy （SEM）， transmission electron microscopy （TEM）， Fourier-transform infrared spectroscopy （FT-IR）， X-ray diffraction （XRD）， and nitrogen adsorption-desorption isotherms， were employed to confirm the successful synthesis of UiO-66-F₄ crystals. The results demonstrated that the synthesized crystals possessed a high specific surface area （559.5 m²/g） and an irregularly stacked porous structure. The prepared UiO-66-F₄ was subsequently homogenized with a polyacrylonitrile （PAN） solution to form a slurry. This slurry was solidified onto 96 stainless-steel blades using an improved laboratory-developed spraying technique. As a result， an array of 96 UiO-66-F₄/PAN extraction coatings was obtained. Each coating in the array was fabricated with uniform dimensions of 2 cm in length， 0.2 cm in width， and approximately 100 μm in thickness. The relative standard deviations （RSDs， n=8） for the length， width， and thickness of the coatings measured were 0.29%， 0.48%， and 4.64%， respectively. The UiO-66-F₄ adsorbent offers multiple interaction forces with glyphosate， including metal coordination， hydrogen bonding， and electrostatic interactions. Therefore， the adsorption of glyphosate onto UiO-66-F₄ occurred rapidly， reaching equilibrium within 5 min. The pseudo-second-order kinetic model provides a superior fit for the adsorption kinetics behavior of glyphosate on the surface of UiO-66-F₄， suggesting that the adsorption process is predominantly controlled by chemisorption. Furthermore， the glyphosate adsorption isotherms indicate that its adsorption behavior closely conforms to the Langmuir isotherm model （R²>0.97）. This finding suggests that glyphosate is adsorbed as a monolayer on the adsorbent surface， giving rise to a maximum adsorption capacity of 239.4 mg/g. The developed TFME method efficiently enriches glyphosate from aqueous solutions at pH 5–7 within 30 min and allows for analyte desorption using an aqueous solution containing 5% （V/V） triethylamine. The UiO-66-F₄/PAN coatings displayed high repeatability and reproducibility， as evidenced by the RSD values below 2.3% （n=5）. In addition， the coatings exhibited remarkable robustness， maintaining a recovery of 98.2% after nine consecutive TFME processing cycles. Furthermore， coupling this TFME method with ultra performance liquid chromatography-tandem mass spectrometry （UPLC-MS/MS） enabled high-throughput analysis of glyphosate. The method demonstrated excellent linearity over a range of 0.5–500 ng/mL （R²=0.999 9）. The limits of detection （LOD） and quantification （LOQ） were 0.12 ng/mL and 0.5 ng/mL， respectively. Intra-day （n=3） and inter-day （n=5） precisions， expressed as RSDs， were 3.6% and 1.6%， respectively. The method was successfully applied to real-world environmental water and fruit samples， detecting glyphosate residues of （1.7±0.7） ng/g in orange peel and （1.2±0.5） ng/mL in irrigation river water. Spiked recoveries in real samples ranged from 88.1% to 107.1%， with precisions （RSDs， n=3） below 8.1%. This method is accurate， reliable， and reproducible， enabling parallel processing of 96 samples， which are well-suited for rapid screening and precise quantification of glyphosate contamination in large-scale sample analyses.

Key words: metal-organic frameworks （MOFs）, array-type thin-film microextraction, glyphosate, high-throughput analysis