Cucurbit[7]uril as a matrix solid-phase dispersion for the extraction of quaternary ammonium pesticides from vegetables and their determination using HPLC-UV

The tightest self-assembled ruthenium metal-organic framework combined with proximity hybridization for ultrasensitive electrochemiluminescence analysis of paraquat

Metal-organic frameworks (MOFs), as porous materials, have great potential for exploring high-performance electrochemiluminescence (ECL) probes. However, the constrained applicability of MOFs in the realm of ECL biosensing is primarily attributed to their inadequate water stability, which consequently impairs the overall ECL efficiency. Herein, we developed a competitive ECL biosensor based on a novel tightest structural ruthenium-based organic framework emitter combining the proximity hybridization-induced catalytic hairpin assembly (CHA) strategy and the quenching effect between the Ru-MOF and ferrocene for detecting paraquat (PQ). Through a simple hydrothermal synthesis strategy, ruthenium and 2,2'-bipyrimidine (bpm) are head-to-head self-assembled to obtain a novel tightest structural Ru-MOF. Due to the metal-ligand charge-transfer (MLCT) effect between ruthenium and the bpm ligand and the connectivity between the internal chromophore units, the Ru-MOF exhibits strong ECL emissions. Meanwhile, the coordination-driven Ru-MOF utilizes strong metal-organic coordination bonds as building blocks, which effectively solves the problem of serious leakage of chromophores caused by water solubility. The sensitive analysis of PQ is realized in the range of 1 pg/mL to 1 ng/mL with a detection limit of 0.352 pg/mL. The tightest structural Ru-MOF driven by the coordination of ruthenium and bridging ligands (2,2'-bipyrimidine, bpm) provides new horizons for exploring high-performance MOF-based ECL probes for quantitative analysis of biomarkers.

A new colorimetric aptasensor for paraquat detection based on the designed aptamer with multiple paraquat binding sites in combination with gold nanoparticles

The presence of paraquat in the environment poses a danger to human health, leading to a growing demand for an uncomplicated and highly responsive method to detect paraquat. This work reports a new, simple, and sensitive colorimetric aptasensor based on the designed aptamers containing 1-5 paraquat binding sites (R1-R5) in combination with gold nanoparticles (AuNPs). Although the aptamers with more binding sites exhibited greater paraquat interaction capability, the aptasensor based on the R3 aptamer showed the highest detection sensitivity for paraquat in a linear range of 5-50 nM with a limit of detection of 1.29 nM, meaning that it is 2.14 fold more sensitive than the R1-aptasensor. This R3-aptasensor selectively detected paraquat but not the other tested herbicides, including difenzoquat, 2,4-D, ametryn, atrazine, and glufosinate. Also, it efficiently detected paraquat spiked in water samples within the precision acceptance criterion of recovery rates (96.8-105.0%) and the relative standard deviations (1.50-3.81%). These results demonstrated the development of a new aptasensor for paraquat detection, in which the multiple paraquat binding sites of the aptamers could enhance detection sensitivity.

A dual-mode sensor platform with adjustable electrochemiluminescence-fluorescence for selective detection of paraquat pesticide

This study presents functionalized metal-organic frameworks nanosheets (RuMOFNSs) with strong electrochemiluminescence (ECL) and fluorescence (FL) properties and a novel signal marker-tetraferrocene. Based on the efficient quenching effect of the tetraferrocene on RuMOFNSs, a "signal switch" ECL-FL dual-mode sensor is constructed for sensitive detection of paraquat (PQ). ECL and FL signals are annihilated after adding paraquat-aptamer DNA (PQ-Apt DNA) labeled with tetraferrocene since it is close to RuMOFNSs. PQ is added, and the strong binding and intermolecular interaction between PQ-Apt DNA and PQ induces spatial separation, with tetraferrocene groups far away from RuMOFNSs. At this point, ECL and FL signals are restored. The change in ECL and FL signals realized the quantitative determination of the PQ solution. In addition, the dual-mode sensor exhibits high sensitivity and specificity with detection limits as low as 0.008 ng/mL and 0.059 ng/mL. The proposed sensor is successfully applied to determine PQ, indicating its great application potential in the food industry.

Nanographite-assisted matrix solid phase dispersion microextraction of active and toxic compounds from complex food matrices using cyclodextrin aqueous solution as elution solvent

In this study, a cyclodextrin aqueous solution was used as an environmentally friendly eluent to simultaneously extract active and toxic compounds from food matrices with the aid of nanographite-assisted matrix solid phase dispersion microextraction (NG-MSPDM). The NG-MSPDM procedure was optimized by single-factor experiments and response surface methodology to obtain optimum conditions. The proposed method achieved excellent linearity at 0.10-20 μg/mL for all target analytes with a coefficient of correction (R²) ≥ 0.9909, limits of detection < 52.01 ng/mL, satisfactory reproducibility below 3.21 %, and acceptable recoveries of 82.0-112 %. To accurately determine the target components in the complex matrix, collision cross-section values of the analytes were obtained using ion mobility quadrupole time-of-flight mass spectrometry (IM-Q-TOF/MS). Results indicated that the NG-MSPDM method successfully achieved the simultaneous extraction of flavonoids and phenoxyacetic herbicides from Alpinia officinarum.

Matrix solid-phase dispersion based on cucurbit[7]uril-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography for the determination of benzimidazole fungicides from vegetables

A new method involving matrix solid-phase dispersion (MSPD) and dispersive liquid-liquid microextraction (DLLME) was optimized with the aid of stoichiometry and applied to the extraction, purification, and determination of benzimidazole residues in vegetables. Carbendazim, thiabendazole, and thiophanate-methyl were selectively extracted from vegetables using cucurbit[7]uril as the MSPD extractant and transferred to an aqueous solution, then further enriched using DLLME with acetonitrile and chloroform as dispersive and extraction solvents, respectively. The optimal extraction conditions of MSPD and DLLME were selected by two-level full-factorial design and central-composite design (CCD). The developed method (MSPD-DLLME-HPLC-UV) showed good linearity in the range of 0.025-5 μg/g, with R² > 0.9984. Intra- and interday precisions were 5.3-10.9% and 10.6-12.4%, respectively, and the limit of detection was between 0.004 and 0.007 μg/g of fresh weight. This method was applied to the analysis of four different types of vegetables, and the recoveries ranged from 65.4% to 124.0%. The method was environmentally friendly, easy to operate, and sensitive.