Background: Paraquat and diquat are widely used in agricultural production in many countries, which are very toxic to human beings. Paraquat can be detected in some diquat solution sold in the market. The blood concentration of paraquat or diquat is an important indicator for clinical diagnosis of paraquat or diquat poisoning. So, it is very meaningful to develop a method for simultaneous determination of paraquat and diquat in human plasma.Objective: To develop and validate a HPLC‐DAD method for simultaneous determination of paraquat and diquat in human plasma and to apply it in the acute poisoning patients by these two herbicides.Methods: Paraquat and diquat were simultaneously determined by HPLC‐DAD. The plasma was treated using Waters OASIS^® Column and then separated on a Thermo Hypersil GOLD (250 × 4.6 mm, 5 μm) Column with the mobile phase consisted of 75 mmol/L sodium heptane sulfonate (containing 0.1 mol/L phosphoric acid, pH 3.0) and acetonitrile (87:13, v:v) at a flow rate of 1.0 mL/min. The full‐wavelength scanning was 200‐400 nm, and the detection wavelength of paraquat and diquat was 257nm and 310nm, respectively. 120 and 30 plasma samples from patients with paraquat and diquat poisoning were collected and analyzed by the established method.Results: The standard curve for paraquat and diquat ranged from 0.05 to 20 μg/mL, and the precision of LLOQ for paraquat was 16.49%, which was required to be less than 20%. The precision of other concentrations was less than 14.14%. The recovery of paraquat and diquat was 95.38%‐103.97% and 94.79%‐98.40%, respectively. The results showed that paraquat and diquat were stable under various storage conditions. 120 plasma samples of paraquat poisoning patients and 30 plasma samples of diquat poisoning patients were determined by the established method. The blood concentration of paraquat ranged from 0.10 to 20.62 μg/mL, with an average of 3.61 μg/mL, while for diquat, the concentration ranged from 0 to 26.59 μg/mL, with an average of 2.00 μg/mL. Among the diquat suspected poisoning samples, 5 samples were detected not only diquat but also paraquat, and 2 samples were detected only paraquat, no diquat.Conclusion: The HPLC‐DAD method established in this study was high throughput, high sensitivity, simple operation, and wide linear ranges. It can be used for the screening analysis and quantitative detection of paraquat and diquat in acute poisoning patients, which can provide basis for the treatment and prognosis of these two herbicides poisoning patients.

In this study, magnetic amino-modified silica nanospheres (Fe₃O₄@SiO₂@NH₂) were prepared via coating 3-aminopropyltriethoxysilane on the surface of Fe₃O₄ magnetite and used for the extraction of free fatty acids (FFAs) from edible oil samples for the first time. Fourier transform infrared spectroscopy and vibrating sample magnetometer analysis indicated that Fe₃O₄@SiO₂@NH₂ was successfully synthesized and exhibited superparamagnetism. The static and dynamic adsorption experiments showed that Fe₃O₄@SiO₂@NH₂ exhibited rapid adsorption equilibrium and satisfactory adsorption capacity towards FFAs. Under optimized adsorption and analytical conditions, Fe₃O₄@SiO₂@NH₂ could effectively extract FFAs from edible oil samples with excellent linearities (0.2–1000 nmol g⁻¹), extremely low limits of detection (0.09–0.46 nmol g⁻¹), and satisfactory recoveries (77.4–101.8%) and precisions (3.1–9.6%). Moreover, compared to classic solid phase extraction using a commercial cartridge, the current magnetic solid phase microextraction method has many advantages including easier preparation of adsorbents, a simpler sample handling procedure and lower cost. Therefore, this method provides a promising alternative to the traditional method for the analysis of FFAs to ensure the sanitation and quality of oils.

Magnetic molecularly imprinted polymers (MMIPs) were prepared with isoprocarb as template molecule and applied to extraction of carbamates pesticides in different water samples. This method based on magnetic solid-phase extraction (SPE) avoided the time-consuming column-passing process of loading large volume samples in conventional SPE. In the study, only 0.1 g MMIPs could be used to obtain satisfactory recoveries, due to the high-surface area and excellent adsorption capacity of these nano-magnetic adsorbents. Owing to the excellent selectivity of MMIPs, in high-performance liquid chromatography–mass spectrometry analysis, the matrix effects of this technique were obviously lower than the conventional SPE method. Under the optimal conditions, the detection limits of carbamates were in the range of 2.7–11.7 ng L⁻¹. The relative standard deviations of intra-day and inter-day were 2.5–7.4% and 3.6–8.4%, respectively. At all the spiked level, the recoveries of four analyzed carbamates in environmental water samples were in the range of 74.2–94.2%. The significant positive results were achieved in the proposed method for the determination of four carbamates in water samples from different lakes and rivers. In the three samples we tested, the carbaryl was found in the lake water obtained from Yitong River, and the content was 2.4 ng L⁻¹.