Ionic liquid-based cloud point extraction five organophosphorus pesticides in coarse cereals

Dispersive liquid‒liquid microextraction combined with enzyme-linked immunosorbent assay for the analysis of chlorpyrifos in cereal samples

In this paper, an analysis method for chlorpyrifos (CPF) in cereal samples was proposed using dispersive liquid‒liquid microextraction combined with an enzyme-linked immunosorbent assay. In the dispersive liquid‒liquid microextraction, deep eutectic solvents and fatty acids were used as solvents to extract, purify, and concentrate CPF in cereals. In the enzyme-linked immunosorbent assay, gold nanoparticles were utilized to enrich and conjugate more antibodies and horseradish peroxidase, while magnetic beads were used as solid supports to amplify the signal and shorten the detection time of CPF. The linearity range was 0.002-1 μg kg-1, and the limit of detection was 0.0006 μg kg-1. The extraction recoveries were 86.7-99.9% with a relative standard deviation of less than 7.0%. The proposed method was successfully used to analyze CPF in cereal samples (rice, wheat, maize, and millet) and has prospects for the pretreatment and detection of CPF residues in other food samples.

Sensitive fluorescent detection of phosmet and chlortetracycline in animal-derived food samples based on a water-stable Cd(II) chain-based zwitterionic metal-organic framework

The residues of pesticides and antibiotics have always been a major concern in agriculture and food safety. In order to provide a new method for the rapid detection of organophosphorus pesticides and antibiotics, a novel Cd(II) chain-based zwitterionic metal-organic framework MOF 1 with high sensitivity fluorescence sensing performance was successfully synthesized. A series of researches showed that the water- and pH-stable bifunctional MOF 1 has a great ability to detect phosmet (PSM) and chlortetracycline (CTC) in water through fluorescence quenching effect, with high detection sensitivity, low detection limits (0.0124 μM and 0.0131 μM), short response time (40 s) and reusability. Practical application results revealed that MOF 1 could detect PSM and CTC in milk, beef, chicken and egg samples, with satisfactory recoveries (95.2%-103.7%). As a novel fluorescence probe, MOF 1, is known the first case that can detect PSM in animal-derived samples, and the first dual-function material capable of detecting PSM and CTC. Mechanism studies displayed that competitive absorption and photoinduced electron transfer clearly authenticate the high quenching performance of the material.

Innovative approaches in cloud-point extraction

Cloud-point extraction (CPE) is a pre-treatment technique for the extraction and preconcentration of different chemical compounds, such as metal ions, pesticides, drugs, phenols, vitamins etc., from various samples. CPE is based on the phenomenon of two phases (micellar and aqueous) forming after the heating of an aqueous isotropic solution of a non-ionic or zwitterionic surfactant above the cloud-point temperature. If analytes are added to the surfactant solution under suitable conditions, they should be extracted into the micellar phase, also called the surfactant-rich phase. Recently, the traditional CPE procedure is being increasingly replaced by improved CPE procedures. In this study, recent advances in CPE over the last three years (2020 - 2022), including the application of various innovative approaches, are reviewed. In addition to the basic principle of CPE, alternative extraction media in CPE, CPE supported by various auxiliary energies, a different modified CPE procedure and the use nanomaterials and solid-phase extraction in combination with CPE are presented and discussed. Finally, some future trends for improved CPE are presented.

Highly defective copper-based metal-organic frameworks for the efficient adsorption and detection of organophosphorus pesticides: An experimental and computational investigation

Organophosphorus pesticide (OP) residues pose a serious threat to human health, motivating the search for novel adsorbents and detection methods. Herein, defective copper-based metal organic frameworks (Cu-MOFs) were synthesized by the reaction of Cu²⁺ ions and 1,3,5-benzenetricarboxylate linkers in the presence of acetic acid. As the amount of acetic acid increased, the crystallization kinetics and morphology of the Cu-MOFs changed, leading to mesoporous Cu-MOFs with many large surface pores (defects). Adsorption studies of OPs revealed the defective Cu-MOFs showed faster pesticide adsorption kinetics and higher pesticide adsorption capacities. Density functional theory calculations showed that pesticide adsorption in the Cu-MOFs was mainly electrostatic. A dispersive solid phase extraction method was developed based on a defective Cu-MOF-6 for rapidly extracting pesticides from food samples. The method allowed pesticide detection over a wide linear concentration range, low limits of detection (0.0067-0.0164 µg L^-1) and good recoveries in pesticide-spiked samples (81.03-109.55%).

Determination of organophosphorus in dairy products by graphitic carbon nitride combined molecularly imprinted microspheres with ultra performance liquid chromatography

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An OPP-based molecularly imprinted microsphere was synthesized.

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Composite material was synthesized by polymerizing the MIM on the surface of g-C₃N₄.

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A novel SPE cartridge was prepared by using the composite material MIM/g-C₃N₄.

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An SPE-UPLC method was developed for the detection of OPPs in dairy products.

Organophosphorus (OPPs) residues in dairy products are a potential threat to human health. To extract trace amounts of OPPs in dairy products, a graphitic carbon nitride (g-C₃N₄) was synthesized and combined with OPPs-based molecularly imprinted microspheres (MIM) to create a composite material (MIM/g-C₃N₄). Then, the MIM/g-C₃N₄ was used to prepare a solid phase extraction (SPE) cartridge to detect the OPPs in dairy products with UPLC method. The specific surface area of MIM/g-C₃N₄ was 172.208 m²/g, good thermal stability under 300℃, and could reuse up to 15 times. The four OPPs had good linear relationship within the range of 1–10000 ng/mL (r² > 0.999). The limits of detection were 0.7–2.6 ng/mL, and recoveries from blank dairy samples were 86.4 to 95.3 %. In this study, MIM combined with g-C₃N₄ was firstly utilized for the detection of OPPs in dairy products, which indicated it might be an ideal adsorbent for dairy products pretreatment.