Simultaneous detection of four pesticides in agricultural products by a modified QuEChERS method and LC-MS/MS.

A modified QuEChERS pretreatment method and LC-MS/MS technique were performed to simultaneously determine four pesticide (Hexachlorophene, Dinex, Dinosam, Dinoterb) residues in agricultural products. Through the optimization of LC-MS/MS detection parameters in SIM mode, the optimal instrument conditions are obtained. The modified QuEChERS method was used to pretreat the samples. Solid phase extractants PSA, C18 and GCB were used for sample purification. The research results showed that the correlation coefficients of the four pesticides were all greater than 0.991, which had a good linear relationship. The limits of quantitation (LOQ) of the four pesticides were 0.05-0.56 µg/kg. The recoveries were 70.51-113.20% with relative standard deviations (RSDS) of 1.6-11.2%. The developed method can provide reliable data support for the subsequent simultaneous detection of these four pesticides.

Establishment of an LC-MS/MS Method for the Determination of 45 Pesticide Residues in Fruits and Vegetables from Fujian, China.

Pesticide residues in food have become an important factor seriously threatening human health. Therefore, this study was conducted to determine the pesticide residues in fruits and vegetables commonly found in Fujian, China, with the aim of constructing a simple and rapid method for pesticide residue monitoring. We collected 5607 samples from local markets and analyzed them for the presence of 45 pesticide residues. A fast, easy, inexpensive, effective, robust, and safe (QuEChERS) multi-residue extraction method followed by liquid chromatography equipped with triple-quadrupole mass spectrometry (LC-MS/MS) was successfully established. This 12-min-long analytical method detects and quantifies pesticide residues with acceptable validation performance parameters in terms of sensitivity, selectivity, linearity, the limit of quantification, accuracy, and precision. The linear range of the calibration curves ranged from 5 to 200 mg/L, the limits of detection for all pesticides ranged from 0.02 to 1.90 µg/kg, and the limits of quantification for the pesticides were 10 µg/kg. The recovery rates for the three levels of fortification ranged from 72.0% to 118.0%, with precision values (expressed as RSD%) less than 20% for all of the investigated analytes. The results showed that 726 (12.95%) samples were contaminated with pesticide residues, 94 (1.68%) samples exceeded the maximum residue limit (MRL) of the national standard (GB 2763-2021, China), 632 (11.23%) samples were contaminated with residues below the MRL, and 4881 (87.05%) samples were pesticide residue-free. In addition, the highest number of multiple pesticide residues was observed in bananas and peppers, which were contaminated with acetamiprid, imidacloprid, pyraclostrobin, and thiacloprid.

The thermal expansion exfoliation technology and lithium promoter assistant afford CuOx/graphene as a high-performance anode for lithium-ion batteries.

The ability to rationally design a copper oxide anode with superior rate performance that possesses an ultra-small particle size is highly desirable for lithium-ion batteries (LIBs). Herein, the rapid and effective thermal expansion exfoliation technology was employed to synthesize ultra-small CuOx nanoparticles (∼2.7 nm) uniformly dispersed on graphite oxide after popping (CuOx/Li-PGO), in which the addition of lithium promoted the exfoliation process to obtain an enlarged specific surface area and efficient transfer ability of PGO. The CuOx/Li-PGO electrode achieved a reversible capacity as high as 512.1 mA h g-1 under 2.0 A g-1 after 1000 cycles, demonstrating superior rate performance and cycling stability.

One-dimensional N-doped carbon nanofibers produced by pre-oxide treatment for effective lithium storage.

Amorphous carbon materials have been confirmed as attractive anode materials for lithium-ion batteries. Herein, an effective strategy to fabricate amorphous carbon materials at low temperature under air atmosphere is proposed. As demonstrated, one-dimensional nitrogen-doping carbon nanofibers were obtained through simple electrospinning technology, following low-temperature heat treatment. Meanwhile, the nitrogen-doping concentration can be regulated by the heating temperature, which can further introduce different levels of adsorption sites on the surface of carbon and enhance the electronic conductivity. Based on experimental investigation, carbon nanofibers with a high nitrogen doping concentration of 18.1 at% achieved an outstanding cycling durability (194.0 mA h g-1 at 2.0 A g-1 after 2000 cycles).

[Two sample pretreatment methods and their applications in the determination of 111 pesticides and related chemicals in aquatic products].

Two sample pretreatment methods were developed and applied to determine 111 residues of pesticides in aquatic products. For Method I, the residues were extracted from homogenized tissue with acetone-ethylacetate-n-hexane (1 : 1 : 1, v/v/v), and then were redissolved in acetonitrile; for Method II, the residues were extracted from homogenized tissue with acetonitrile - water under ultrasonication, and then were separated by liquid-liquid partition. The supernatants were purified using solid phase extraction (Envi-18 and PSA columns) prior to the GC-MS analysis. The determination was performed in selected ion monitoring (SIM) mode with the external calibration for quantitative analysis. Under the optimal conditions, the detection limits (S/N = 3) for residues of pesticides were in the ranges of 0.001 -0.026 mg/kg. The recoveries of Method I for the spiked standards at concentration of 0.25 mg/kg were 72% - 113% with the relative standard deviations (RSDs) of 3.4% - 12.1%. The recoveries of Method II were 51% - 127%, among which the recoveries for 94% pesticides were between 70% and 120% with the RSDs of 3.2% - 13.8%.