Solid-Phase Microextraction Combined with GC–MS for Determination of Diquat and Paraquat Residues in Water

Ratiometric emission of Tb(III)-functionalized Cd-based layered MOFs for portable visual detection of trace amounts of diquat in apples, potatoes and corn

Diquat (DQ) is a typical bipyridine herbicide widely used to control weeds in fields and orchards. The severe toxicity of diquat poses a serious threat to the environment and human health. Metal-organic frameworks (MOFs) have received widespread attention due to their unique physical and chemical properties and applications in the detection of toxic and harmful substances. In this work, a two-dimensional (2D) Tb(III) functionalized MOF Tb(III)@1 (1 = [Cd(HTATB)(bimb)]n·H2O (Cd-MOF), H3TATB = 4,4',4″-triazine-2,4,6-tribenzoicacid, bimb = 1,4-bis((1H-imidazol-1-yl)methyl)benzene) has been prepared and characterized. Tb(III)@1 has excellent optical properties and high water and chemical stability. After the Tb(III) is fixed by the uncoordinated -COO- in the 1 framework, Tb(III)@1 emits the typical green fluorescence of the lanthanide ion Tb(III) through the "antenna effect". It is worth noting that Tb(III)@1 can be used as a dual emission fluorescence chemical sensor for the ratio fluorescence detection of pesticide DQ, exhibiting a relatively low detection limit of 0.06 nM and a wide detection range of 0-50 nM. After the addition of DQ, a rapid color change of Tb(III)@1 fluorescence from green to blue was observed due to the combined effects of IFE, FRET and dynamic quenching. Therefore, a simple test paper box has been designed for direct on-site determination of pesticide DQ. In addition, the developed sensor has been successfully applied to the detection of DQ in real samples (fruits a Yin-Xia Sun and Bo-Tao Ji contributed equally to this work and should be considered co-first authors.nd vegetables) with satisfactory results. The results indicate that the probe developed in this study has broad application prospects in both real sample detection and actual on-site testing.

Aptamer-enhanced the Ag(I) ion-3,3',5,5'-tetramethylbenzdine catalytic system as a novel colorimetric biosensor for ultrasensitive and selective detection of paraquat

A facile and simple colorimetric biosensor was first established for paraquat (PQ) detection based on the aptamer-enhanced oxidation process of 3,3',5,5'-tetramethylbenzidine (TMB) by Ag⁺. The study confirmed that the interaction of PQ-15 aptamer with Ag⁺ accelerates the electron transfer from the aptamer-Ag⁺ complex to dissolved oxygen, which enhances the release of superoxide anion radicals (O₂̇^-) and facilitates the catalytic oxidation of the chromogenic substrate. PQ-15 aptamer will preferentially bind to PQ molecules, resulting in no further enhancement of the catalytic activity of Ag⁺. Molecular docking results revealed that the PQ molecules are attached to the stem-loop region of the PQ-15 aptamer through σ-π conjugation interactions. The proposed method is simple that only contains Ag⁺ and corresponding aptamer. The limit of detection (LOD) of the constructed colorimetric biosensor for PQ detection was determined to be 16.5 μg·L^-1, belowing the maximum residue limit in fruits and vegetables set by the EU. Moreover, the colorimetric biosensor showed excellent selectivity and anti-interference properties, which was validated for detecting PQ residues in several typical agricultural and water samples.

Solar Photo-Assisted Degradation of Bipyridinium Herbicides at Circumneutral pH: A Life Cycle Assessment Approach

This study investigated the degradation of the herbicides diquat (DQ) and paraquat (PQ) by a solar photo-Fenton process that is mediated by Fe(III)-oxalate complexes at circumneutral pH = 6.5 in compound parabolic collectors (CPC)-type reactors. The photo-Fenton process operates efficiently at acidic pH; however, circumneutral operation was key to overcome drawbacks, such as acidification and neutralization steps, reagent costs, and the environmental footprint of chemical auxiliaries. This work revealed a remarkable reduction of total organic carbon for PQ (87%) and DQ (80%) after 300 min (at ca. 875 kJ L−1). Phytotoxicity assays confirmed that the treatment led to a considerable increase in the germination index for DQ (i.e., from 4.7% to 55.8%) and PQ (i.e., from 16.5% to 59.7%) using Cucumis sativus seeds. Importantly, treatment costs (DQ = USD$8.05 and PQ = USD$7.72) and the carbon footprint of the process (DQ = 7.37 and PQ = 6.29 kg CO2-Eqv/m3) were within the ranges that were reported for the treatment of recalcitrant substances at acidic conditions in CPC-type reactors. Life cycle assessment (LCA) evidenced that H2O2 and electricity consumption are the variables with the highest environmental impact because they contribute with ca. 70% of the carbon footprint of the process. Under the studied conditions, a further reduction in H2O2 use is counterproductive, because it could impact process performance and effluent quality. On the other hand, the main drawback of the process (i.e., energy consumption) can be reduced by using renewable energies. The sensitivity study evidenced that carbon footprint is dependent on the energy share of the local electricity mix; therefore, the use of more renewable electrical energy sources, such as wind-power and photovoltaic, can reduce greenhouse gases emissions of the process an average of 26.4% (DQ = 5.57 and PQ = 4.51 kg CO2-Eqv/m3) and 78.4% (DQ = 3.72 and PQ = 2.65 kg CO2-Eqv/m3), respectively. Finally, from the economic and environmental points of view, the experimental results evidenced that photo-assisted treatment at circumneutral pH is an efficient alternative to deal with quaternary bipyridinium compounds.

An Ionic Liquid-based Microextraction Method for Ultra-High Preconcentration of Paraquat Traces in Water Samples Prior to HPLC Determination

An ionic liquid (IL)-based microextraction method was developed for the preconcentration of paraquat traces in water samples prior to HPLC determination. On the basis of the relationship between the aqueous solubility and the extractability of known ILs, 1-ethyl-3-methylimidazolium bis(nonafluorobutanesulfonyl)amide ([EMIm][NNf₂]) was selected as the extractant for paraquat. The distribution ratio of paraquat dication in the [EMIm][NNf₂]/water biphasic system was theoretically estimated to be nearly 10⁸ at its maximum level, indicating that [EMIm][NNf₂] was suitable for the ultra-high preconcentration (a maximum of 10⁶-fold concentration) of paraquat with a quantitative recovery (more than 99%). The extraction procedure could be performed easily and quickly following the in situ solvent formation microextraction technique, and the paraquat traces in the IL phase could be determined by hydrophilic interaction chromatography with good detection limits and linearity ranges (0.16 and 1 - 50 ng mL^-1 for paraquat, respectively). The combined method was successfully applied to four real environmental water samples spiked with paraquat and its analog, diquat at 5.0 ng mL^-1.

Large volume of water samples introduced in dispersive liquid-liquid microextraction for the determination of 15 triazole fungicides by gas chromatography-tandem mass spectrometry

A novel method of large volume of water samples directly introduced in dispersive liquid-liquid microextraction was developed, which is based on ultrasound/manual shaking-synergy-assisted emulsification and self-generating carbon dioxide gas (CO2) breaking down the emulsion for the determination of 15 triazole fungicides by gas chromatography-tandem mass spectrometry. This technique makes low-density extraction solvent toluene (180 μL) dissolve in 200 mL of samples containing 0.05 mol L(-1) of HCl and 5 % of NaCl (w/v) to form a well emulsion by synergy of ultrasound and manual shaking, and injects NaHCO3 solution (1.0 mol L(-1)) to generate CO2 achieving phase separation with the assistance of ultrasound. The entire process is accomplished within 8 min. The injection of NaHCO3 to generate CO2 achieves phase separation that breaks through the centrifugation limited large volume aqueous samples. In addition, the device could be easily cleaned, and this kind of vessel could be reconfigured for any volume of samples. Under optimal conditions, the low limits of detection ranging from 0.7 to 51.7 ng L(-1), wide linearity, and enrichment factors obtained were in the range 924-3669 for different triazole fungicides. Southern end of the Beijing-Hangzhou Grand Canal water (Hangzhou, China) was used to verify the applicability of the developed method. Graphical Abstract Flow chart of ultrasound/manual shaking-synergy-assisted emulsification and self-generating carbon dioxide gas breaking down the emulsion.

A high-performance “sweeper” for toxic cationic herbicides: an anionic metal–organic framework with a tetrapodal cage

High efficiency adsorption and removal of toxic herbicides in an anionic metal–organic framework.