Core-shell ZnO@CoO nitrogen doped nano-composites as highly sensitive electrochemical sensor for organophosphate pesticides detection.

Core-shell ZIF-8@ZIF-67 was synthesized by growing a cobalt-based ZIF-67 on a ZIF-8 seed particle. Herein, through selective etching of the ZIF-8@ZIF-67 core and subsequent direct carbonization, core-shell hollow ZnO@CoO nitrogen-doped nanoporous carbon (HZnO@CoO-NPC) nanocomposites were prepared. HZnO@CoO-NPCs possessed a high nitrogen content, large surface area, high degree of graphitization and excellent electrical conductivity, all of which were attributed to successfully integrating the unique advantages of ZIF-8 and ZIF-67. HZnO@CoO-NPCs were used to assemble acetylcholinesterase (AChE) biosensors for organophosphorus pesticides (OPs) detection. The low detection limit of 2.74 × 10-13 M for chlorpyrifos and 7.6 × 10-15 M for parathion-methyl demonstrated the superior sensing performance. The results showed that the electrochemical biosensor constructed by HZnO@CoO-NPC provided a sensitive and efficient electrochemical strategy for OPs detection.

Wide-Scope Multi-residue analysis of pesticides in beef by gas chromatography coupled with quadrupole Orbitrap mass spectrometry.

Increasing pesticide contamination in foods of animal origin has made the wide-scope multi-residue analysis of pesticides an international concern. By using 191 pesticides, this study investigates a sensitive and reliable method for multi-residue analysis of pesticides in beef to determine the extent of the application of this method. The QuEChERS method was employed to extract and purify the pesticides as C18 was utilized as the absorbents. Then, the purified pesticides were analysed using gas chromatography - quadrupole orbitrap mass spectrometry (GC-Q-Orbitrap-MS). The validation test results revealed that this method was satisfactorily sensitive since its screening detection limit (SDL) ranged from 0.2 to 100 µg∙kg-1. The recovery tests implemented at three spiking levels, namely 100, 200, and 500 µg∙kg-1, generated the results of 71.95 %-113.97 %, while the intra- and inter-day precisions were 0.27 %-17.94 %, indicating that this method had excellent accuracy and precision.

Delivery of Curcumin Using Zein-Gum Arabic-Tannic Acid Composite Particles: Fabrication, Characterization, and in vitro Release Properties.

The application of curcumin (Cur) in fat-free food is limited due to its poor water solubility, stability, and bioaccessibility. In this study, zein-gum arabic-tannic acid (zein-GA-TA) composite particles with high physical stability were fabricated to deliver Cur (ZGT-Cur). Their stability and in vitro release properties were also evaluated. The results showed that the thermal and photochemical stability of Cur was improved after loading into composite particles. Meanwhile, the retention rate of Cur in ZGT-Cur composite particles was enhanced compared with Z-Cur or ZG-Cur particles. Fourier transform infrared (FTIR) spectroscopy confirmed that the hydrogen bond within the particles was greatly enhanced after the addition of tannic acid (TA). The in vitro antioxidant activity of Cur in ZGT-Cur composite particles was higher in terms of 2,2'-azino-bis (ABTS) (93.64%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) (50.41%) compared with Z-Cur or ZG-Cur particles. The bioaccessibility of Cur in ZGT-Cur composite particles was 8.97 times higher than that of free Cur. Therefore, the particles designed in this study will broaden the application of Cur in the food industry by improving its stability and bioaccessibility.

A dummy molecularly imprinted solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry for selective determination of four pyridine carboxylic acid herbicides in milk.

We aim to develop a solid-phase extraction (SPE) based on a dummy molecularly imprinted polymer (MIP) and liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) for selective determination of four pyridine carboxylic acid herbicides (aminopyralid, picloram, fluroxypyr, and clopyralid) in milk samples. Using picloram as the dummy template, MIP nanocomposites with highly selective recognition and adsorption for the target molecule and its structural analogs were successfully synthesized by precipitation polymerization. Adsorption isotherms and kinetics were used to determine the adsorption performance and specific recognition mechanism of both MIPs and non-molecularly imprinted polymers (NIP). The Scatchard plot analysis revealed that two different binding sites were formed in the MIP with maximum binding capacity (Qmax) of 1171.8 µg·g-1 and 3022.5 µg·g-1, respectively. Recovery at three spiking levels of 10, 20, and 50 µg·L-1 ranged between 75.3 and 89.8% with relative standard deviations (RSDs) <14.3%.The limit of detection (LOD) was estimated to be 0.124 µg·L-1. Finally, the feasibility of the proposed methodology was successfully applied to quantify aminopyralid and another three pyridine carboxylic acid herbicides in milk.

Mutation at residue 376 of ALS confers tribenuron-methyl resistance in flixweed (Descurainia sophia) populations from Hebei Province, China.

The acetolactate synthase (ALS) inhibitor tribenuron has been used continuously for approximately twenty years as an herbicide in winter wheat fields in China. Flixweed (Descurainia sophia) has evolved resistance to tribenuron, due to multiple amino acid mutations at the 197th residue of ALS. In this study, the molecular basis of tribenuron resistance was investigated using two resistant populations, Xingtai (XT) and Shijiazhuang (SJ), and two susceptible populations, Cangzhou (CZ) and Handan (HD). Whole-plant tests and ALS activity assays showed that the two resistant populations were highly resistant to tribenuron. Targeted amplification of ALS genes from the four populations showed that there were two ALS genes in each population, and both of them were expressed in flixweed; the full coding lengths of the two ALS genes were 1998bp and 2004bp. Mutations related to tribenuron resistance in flixweed were located in only the 1998bp paralog. An ALS activity assay showed that the resistant population SJ displayed slight cross-resistance to florasulam, with a resistance factor of 4.81, but the resistant population XT did not have cross-resistance to florasulam. The resistant population XT was found to carry the previously reported mutation Pro197Ser, but the resistant population SJ carried a different mutation, Asp376Glu, known from other weeds but novel in flixweed. Our results demonstrated that multiple versions of ALS genes exist in flixweed and that mutations at multiple sites may result in ALS-inhibitor resistance in this weed.