Research progress of applications for nano-materials in improved QuEChERS method.

The quick, easy, cheap, effective, rugged, and safe (QuEChERS) approach is widely used in sample pretreatment in agricultural products, food, environment, etc. And nano-materials are widely used in QuEChERS method due to its small size and large specific surface area. In this review, we examine the typical applications of several commonly used nano-materials in improved QuEChERS method. These materials include multi-walled carbon nanotubes (MWCNTs) and their derivatives, magnetic nanoparticles (MNPs), metal organic frameworks (MOFs), covalent organic frameworks (COFs), graphene oxide (GO), lipid and protein adsorbent (LPAS), cucurbituril (CBs), and carbon nano-cages (CNCs), and so on. The strengths and weaknesses of each nano-material are presented, as well as the challenging aspects that need to be addressed in future research. By comparing the applications and the current technology development, this review suggests utilizing artificial intelligence (AI) to screen suitable combinations of purification agents and performing virtual simulation experiments to verify the reliability of this methodology. By doing so, we aim to accelerate the development of new products and decrease the cost of innovation. It also recommends designing smarter pretreatment instruments to enhance the convenience and automation of the sample pretreatment process and reduce the margin for human error.

Simultaneous determination of 14 pesticide residues in tea by multi-plug filtration cleanup combined with LC-MS/MS.

A combined method of multi-plug filtration cleanup (m-PFC) and liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) was established to simultaneously detect 14 pesticides in tea. The pesticides in water-soaked tea were extracted with acetonitrile. Cleanup of tea extract was performed using an m-PFC column packed with multiple cleanup materials: multi-walled carbon nano-tubes (MWCNTs), primary secondary amine (PSA) and anhydrous magnesium sulfate (MgSO4). The cleanup effect of the column was evaluated based on the rates of removal of tea components that interfered with pesticide recovery, henceforth referred to as interference components. Results showed that 14 pesticides had strong linearity in the range of 5-500 µg L-1 (r2 > 0.99). The quantitative limits were within the range of 3-50 µg kg-1. The average recoveries of 14 pesticides spiked into three different blank tea samples (green tea, black tea, oolong tea) at three levels of 0.05, 0.50 and 2.00 mg kg-1 were in the range of 62.3-108.8% with relative standard deviations of 0.2-13.6%. The m-PFC method can greatly improve the efficiency of sample pretreatment. Furthermore, this work provides methodological guidance on how to select cleanup materials and allocate their proportions.

A one adsorbent QuEChERS method coupled with LC-MS/MS for simultaneous determination of 10 organophosphorus pesticide residues in tea.

Tea polyphenols, chlorophyll and lutein generally cause strong matrix effects and challenge analysis of trace substances in tea. Seven frequently used adsorbents were chosen to test removal ability for tea polyphenols, chlorophyll and lutein based on the adsorption isotherm fitting. Results showed that MWCNTs-NH2 demonstrated the strongest removal ability, which may be ascribed to the π-π and electrostatic interaction. Then a method of MWCNTs-NH2 modified QuEChERS coupled with HPLC-MS/MS detection of 10 organophosphorus pesticide residues in tea was developed and validated. Unlike traditional QuEChERS, only one adsorbent (MWCNTs-NH2) was applied in this method to replace the combined effect of various adsorbents, which improved the easiness and generality of the method. The LOQs were 1.7-9.0 µg/kg. The average recovery rate ranged from 72% to 116% with RSDs less than 14%. This study provides a targeted strategy to develop analysis method for trace substances in a complicated matrix.

Synergistic neuroprotective effects of Geniposide and ursodeoxycholic acid in hypoxia-reoxygenation injury in SH-SY5Y cells.

Endoplasmic reticulum stress (ERS) and autophagy activation play important roles in the process of cerebral ischemia/reperfusion (I/R) injury. The synergistic protective effects of Geniposide and ursodeoxycholic acid against cellular apoptosis caused by oxygen-glucose deprivation-reoxygenation (OGD/R) were investigated using a Cell Counting Kit-8 assay, lactate dehydrogenase (LDH) assay, flow cytometry, quantitative polymerase chain reaction (qPCR), and western blotting to examine cellular viability, apoptosis, reactive oxygen species (ROS) levels, mRNA and protein levels, respectively, in relation to ERS and autophagy. We found that pretreatment with Geniposide improved cellular viability. Moreover, treatment with a combination of Geniposide and Tauroursodeoxycholic acid (TUDCA) (GT) protected injured cells better than Geniposide alone. Further studies showed that the increase in cellular ROS levels, and the overexpression of mRNA and proteins related to OGD/R-induced ERS and autophagy, were both counteracted by GT. Our study indicates that the protective effects of GT on OGD/R-induced apoptosis in SH-SY5Y cells are associated with the inhibition of ERS and autophagy.

Dynamics of hybrid switching DS-I-A epidemic model.

In this paper, we investigate a stochastic hybrid switching DS-I-A epidemic model. The extinction and the prevalence of the disease are discussed, and so, the threshold is given. Furthermore, the sufficient conditions for the existence of positive recurrence of the solutions are established by stochastic Lyapunov functions. At last, some examples and simulations are provided to illustrate our results.

[Determination of imidaclothiz in tea by QuEChERS cleanup and liquid chromatography-tandem mass spectrometry].

The method for the determination of imidaclothiz residue in tea by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. The imidaclothiz in tea was extracted by acetonitrile and purified by QuEChERS with PSA (primary secondary amine), C18, GCB (graphitized carbon black) as the adsorbents. The purified solution was centrifuged and the supernatant was diluted with water of equal volume. The separation was performed on a C18 column with a gradient elution program of acetonitrile (containing 0.1% (v/v) formic acid) and water at a flow rate of 0.30 mL/min. The mass spectrometer was carried out with electrospray ion source in the positive mode (ESI+) and selective reaction monitoring (SRM), quantified by external standard solution. The results showed that the mass concentration of imidaclothiz in the range of 1 to 500 µg/L was linearly correlated with the peak area, and the correlation coefficient (r) was 0.999 9. The limit of quantification (LOQ, S/N ≥ 10) was 0.01 mg/kg. The recoveries in oolong tea and green tea at three spiked levels (0.01, 0.3 and 3 mg/kg) varied from 87.0%-101.0% and the relative standard deviations (RSDs, n = 7) were between 2.1% and 13.1%. The real sample tests showed that the method is simple, cheap, accurate, specific, rapid, and suitable for the qualitative and quantitative confirmation of imidaclothiz residue in tea.