Enrichment of neonicotinoid insecticides from lemon juice sample with magnetic three‐dimensional graphene as the adsorbent followed by determination with high‐performance liquid chromatography

A novel 3D‐graphene (3D‐G) magnetic nanomaterial was prepared and used as an adsorbent for the extraction of four neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid, and thiamethoxam) from lemon juice sample. Then, HPLC with UV detection was applied for the determination of the neonicotinoid insecticides desorbed from the 3D‐G magnetic nanomaterial. The main experimental parameters that affect the extraction efficiencies such as the amount of 3D‐G magnetic nanomaterial, sample solution pH, extraction time, salting‐out effect, and desorption conditions were studied and optimized. As a result, the linear concentration range of the method was from 0.3 to 100.0 ng/mL for thiacloprid, from 0.5 to 100.0 ng/mL for imidacloprid and acetamiprid, and from 1.0 to 100.0 ng/mL for thiamethoxam, with correlation coefficients of 0.9965–0.9985, respectively. The LODs of the method based on an S/N of 3 were between 0.08 and 0.2 ng/mL. The enrichment factors obtained were between 67 and 427, and the RSDs (n = 6) were in the range from 4.6 to 7.1%, and the recoveries of the method fell in the range of 88.75 to 111.60%.     

A quick,easy, cheap,effective, rugged,and safe sample pretreatment and liquid chromatography with tandem mass spectrometry method for the simultaneous quantification of 33 mycotoxins in Lentinula edodes

Lentinula edodes, one of the most cultivated edible fungi in the world, are usually neglected for mycotoxins contamination due to the initial thinking of its resistance to mycotoxingenic molds. In the present study, a sensitive and reliable liquid chromatography with tandem mass spectrometry method was developed for the simultaneous quantification of 33 mycotoxins in L. edodes. Targeted mycotoxins were extracted using a quick, easy, cheap, effective, rugged, and safe procedure without any further clean‐up step, and analyzed by liquid chromatography with tandem mass spectrometry on an Agilent Poroshell 120 EC‐C₁₈ column (100 × 3 mm, 2.7 μm) with a linear gradient elution program using water containing 5 mM ammonium acetate and methanol as the mobile phase. After validation by determining linearity (R² > 0.99), sensitivity (LOQ ≤ 20 ng/kg), recovery (73.6–117.9%), and precision (0.8–19.5%), the established method has been successfully applied to reveal the contamination states of various mycotoxins in L. edodes. Among the 30 tested samples, 22 were contaminated by various mycotoxins with the concentration levels ranging from 3.3–28 850.7 μg/kg, predicting that the edible fungus could be infected by the mycotoxins‐producing fungi. To the best of our knowledge, this is the first report about real mycotoxins contamination in L. edodes.     

Development of a solid‐phase microextraction fiber by the chemical binding of graphene oxide on a silver‐coated stainless‐steel wire with an ionic liquid as the crosslinking agent

Graphene oxide was bonded onto a silver‐coated stainless‐steel wire using an ionic liquid as the crosslinking agent by a layer‐by‐layer strategy. The novel solid‐phase microextraction fiber was characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and Raman microscopy. A multilayer graphene oxide layer was closely coated onto the supporting substrate. The thickness of the coating was about 4 μm. Coupled with gas chromatography, the fiber was evaluated using five polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, 1,2‐benzophenanthrene, and benzo(a)pyrene) as model analytes in direct‐immersion mode. The main conditions (extraction time, extraction temperature, ionic strength, and desorption time) were optimized by a factor‐by‐factor optimization. The as‐established method exhibited a wide linearity range (0.5–200 μg/L) and low limits of determination (0.05–0.10 μg/L). It was applied to analyze environmental water samples of rain and river water. Three kinds of the model analytes were quantified and the recoveries of samples spiked at 10 μg/L were in the range of 92.3–120 and 93.8–115%, respectively. The obtained results indicated the fiber was efficient for solid‐phase microextraction analysis.     

Sensitive detection of T4 polynucleotide kinase activity based on coupled exonuclease reaction and nicking enzyme-assisted fluorescence signal amplification

As a prominent member of the 5′-kinase family, T4 polynucleotide kinase (PNK) plays an important role in gene function regulations, and the study of PNK activity and its potential inhibitors is significant for research related to the DNA phosphorylation process. Here, we proposed a novel strategy for the detection of PNK activity and its inhibition, which combines exonuclease enzyme reaction and nicking enzyme-assisted fluorescence signal amplification. Through recycling cleavage of DNA fluorescence probe for signal amplification, a highly sensitive PNK sensing platform is developed, and a very low detection limit of 0.05 mU/mL is achieved, which is better than or comparable to that of the previously reported PNK assays. The present approach adopts a simple separation-free procedure in which the enzyme assay is conducted in homogeneous solutions. Additionally, the inhibitory effects of several known kinase inhibitors on PNK have been successfully detected. Since the proposed assay exhibits the advantages of high sensitivity and simplicity, it holds great potential in providing a promising platform for convenient and highly sensitive detection of PNK activity and its inhibitors.

Solid-phase methylamidation for sialoglycomics by MALDI-MS

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been a major approach for glycan analysis. However, the preferential cleavage of the sialic acid moiety by in- and post-source decay influences the determination of sialylated glycans by MALDI-MS. Many chemical derivatization methods were introduced to stabilize the sialylated glycan during MALDI-MS. Among current derivatization methods, methylamidation is a promising means for simultaneous analysis of natural sialylated glycans regardless of their sialic acid linkage types. Here, a novel derivatization method was developed, in which proteins were conjugated on the solid-phase support in order to stabilize the sialic acids by methylamidation and to reduce sample loss and contamination during the derivatization process. This derivatization strategy was used to investigate N-glycans from fetuin, a glycoprotein containing different types of complex N-glycans. The developed method was also applied to the N-glycan profiling of human serum from patients and healthy volunteers. Results were consistent with N-glycan profiling by HPLC-fluorescence detection. This new method provided a sensitive, simple, and robust approach for profiling glycan structures of complex samples.     

Bimetallic amine-bridged bis(phenolate) lanthanide aryloxides and alkoxides: synthesis,characterization, and application in the ring-opening polymerization of rac-lactide and rac-β-butyrolactone

A series of neutral bimetallic lanthanide aryloxides p-C6H4[OLnL(THF)n]2 [Ln = Y(1), Yb(2), Sm(3)(n = 1) and La(4)(n = 2), L = Me2NCH2CH2N{CH2-(2-O–C6H2–tBu2-3,5)}2] and alkoxides p-C6H4CH2[OLnL(THF)]2 [Ln = Y(5), Yb(6)] supported by an amine-bridged bis(phenolate) ligand have been synthesized through one-pot reactions of Ln(C5H5)3(THF), LH2 with p-benzenediol and 1,4-benzenedimethanol, respectively. All complexes have been fully characterized by elemental analyses, single-crystal X-ray diffraction analysis, and IR and multi-nuclear NMR spectroscopy(in the cases of 1, 4 and 5). Study of their catalytic behavior revealed that, in general, all complexes are efficient initiators for the polymerization of rac-lactide(LA) and rac-β-butyrolactone(BBL), except for 3 and 4 in the case of BBL. The influence imposed by lanthanides of different ionic radii and initiating groups of different structures on the activity, controllability, and stereoselectivity of polymerization were systematically studied and compared. Highly heterotactic PLA(Pr up to 0.99) and syndiotactic PHB(Pr ≈ 0.81) with high molecular weight and narrow polydispersity formed and were automatically capped with hydroxyl functionality at both ends.     

Well‐Defined Flowerlike NdOCl Nanostructures: Nonaqueous Sol–Gel Synthesis,Nanoscale Characterization and Their Magnetic and Photoluminescence Properties

A facile nonaqueous solution route for the fabrication of NdOCl nanostructures based on a ligand‐exchange protocol and further thermal decomposition in organic medium, using only chloride salt as the neodymium source, is reported and the formation mechanism is proposed. The morphology, crystal structure, and chemical compositions of the sample were characterized at the nanoscale. XRD results and selected‐area electron diffraction patterns show that the sample is purely tetragonal NdOCl without any other impurity phases. TEM results show that the NdOCl nanostructures have a well‐defined flowerlike shape, which looks like a chrysanthemum just about to bloom. Magnetization measurements reveal that the NdOCl nanoflowers show room‐temperature ferromagnetism. The photoluminescence properties were also studied. These results are significant for fundamental research and promising applications of rare‐earth‐based nanostructures.     

On the Size Evolution of Monolayer‐Protected Gold Clusters during Ligand Place‐Exchange Reactions: The Effect of Solvents

Ligand place‐exchange (LPE) reactions are extensively applied for the post‐functionalization of monolayer‐protected gold clusters (MPCs) by using excessive incoming ligands to displace initial ones. However, the modified MPCs are often enlarged or degraded; this results in ill‐defined size‐dependent properties. The growth of MPCs essentially involves an unprotected surface that is subsequently has gold atoms added or is fused with other gold cores owing to collision. Reported herein is a guideline for the selection of solvents to suppress unwanted MPC growth. Favorable solvents are those with significant affinity to gold or with low solubility for desorbed ligands because these properties retard LPE reactions and minimize the time available for unprotected gold cores. This finding provides a general and convenient approach to regulate the size of functionalized MPCs.     

Glucose detection at attomole levels using dynamic light scattering and gold nanoparticles

Glucose is directly related to brain activity and to diabetes.Therefore,developing a rapid and sensitive method for glucose detection is essential.Here,label-free glucose detection at attomole levels was realized by detecting the average diameter change of gold nanoparticles(AuNPs)utilizing dynamic light scattering(DLS).Single-strand DNA(ssDNA)adsorbed into the AuNPs’surfaces and prevented them from aggregating in solution that contained NaCl.However,ssDNA cleaved onto ssDNA fragments upon addition of glucose,and these fragments could not adsorb onto the AuNPs’surfaces.Therefore,in high-salt solution,AuNPs would aggregate and their average diameter would increase.Based on monitoring the average diameter of AuNPs with DLS,glucose could be detected in the range from 15 pmol/L to 2.0 nmol/L,with a detection limit of 8.3 pmol/L.Satisfactory results were also obtained when the proposed method was applied in human serum glucose detection.     

Clickable SBA‐15 to Screen Functional Groups for Adsorption of Antibiotics

Pharmaceutical antibiotics, as emerging contaminants, are usually composed of several functional groups that endow them with the ability to interact with adsorbents through different interactions. This makes the preparation of adsorbents tedious and time‐consuming to screen appropriate functionalized materials. Herein, we describe the synthesis of clickable SBA‐15 and demonstrate its feasibility as a screening material for the adsorption of antibiotics based on similar adsorption trends on materials with similar functional groups obtained by a click reaction and cocondensation/grafting methods.