氢化物发生-原子荧光光谱法测定椒目中不同化学形态的砷

结合椒目化学成分的分离提取方法,采用AFS-3100原子荧光光谱法,分析了不同产地椒目中的砷含量及其形态。使用0.45 μm滤膜和混合溶剂提取的方法将椒目中的砷分为悬浮态和可溶态,并使用离子交换树脂将可溶态中的砷分为As(Ⅲ),As(Ⅴ),MMA,DMA,建立了砷的四种形态分离分析方法。结果显示,各产地椒目中均以无机砷为主且As(Ⅴ), 含量较As(Ⅲ)高,甲醇-水(4∶1)对椒目中砷的浸提率高,椒目水可煎出态总砷百分率为53.7%～62.3%。应用本方法对椒目中的砷进行形态分析,回收率在96.0%～101.3%范围内,RSD小于2.66%。表明其灵敏度高,重现性好。     

Separation of Sulfur Species in Water by Co-Electroosmotic Capillary Electrophoresis with Direct and Indirect UV Detection

Co-electroosmotic capillary electrophoresis (co-CZE) with both direct and indirect UV detection was investigated for the separation of sulfur species. With direct UV detection, the separation of S₂O^2? ₃, S₂O^2? ₄ was possible using 20 mM phosphate electrolyte containing 0.75 mM tetradecyltrimethylammonium bromide (TTAB) and 15% acetonitrile. To obtain optimal peak shape and sensitivity using indirect UV detection, a range of background electrolytes (BGEs), including benzoate, phthalate, 2,6-pyridinedicarboxylate (2,6-PDCA) and trimellitate, were examined as the BGEs. Of all the BGEs, 2,6-PDCA gave high selectivity and indirect UV response due to its mobility matching to that of sulfur species and its high absorptivity. Detection limits in range of 3-6 μM were obtained using either direct UV or indirect UV detection. The proposed CZE methods were used for the determination of sulfur species in water samples, and provided fast separation of sulfur species in less than 5 min.     

Species selective preconcentration and quantification of gold nanoparticles using cloud point extraction and electrothermal atomic absorption spectrometry

The determination of metallic nanoparticles in environmental samples requires sample pretreatment that ideally combines pre-concentration and species selectivity. With cloud point extraction (CPE) using the surfactant Triton X-114 we present a simple and cost effective separation technique that meets both criteria. Effective separation of ionic gold species and Au nanoparticles (Au-NPs) is achieved by using sodium thiosulphate as a complexing agent. The extraction efficiency for Au-NP ranged from 1.01 ± 0.06 (particle size 2 nm) to 0.52 ± 0.16 (particle size 150 nm). An enrichment factor of 80 and a low limit of detection of 5 ng L⁻¹ is achieved using electrothermal atomic absorption spectrometry (ET-AAS) for quantification. TEM measurements showed that the particle size is not affected by the CPE process. Natural organic matter (NOM) is tolerated up to a concentration of 10 mg L⁻¹. The precision of the method expressed as the standard deviation of 12 replicates at an Au-NP concentration of 100 ng L⁻¹ is 9.5%. A relation between particle concentration and the extraction efficiency was not observed. Spiking experiments showed a recovery higher than 91% for environmental water samples.     

A multiplex assay to identify 18 European mammal species from mixtures using the mitochondrial cytochrome b gene

A novel species-specific multiplex to identify 18 common European mammalian species (badger, cat, cow, dog, donkey, fox, goat, guinea pig, harvest mouse, hedgehog, horse, house mouse, human, pig, rabbit, rat, red deer and sheep), many of which are often associated with forensic investigations, has been developed. The assay is based on the mitochondrial cytochrome b gene, which is commonly used in species identification and phylogeny studies. Areas of homology and variation were identified and were used to create universal and species-specific primers. The species-specific primers were designed such that they will only react with the species for which they were designed. Two primer sets were designed for each species making the test self-confirmatory. All primer sets produced the expected results. The multiplex was balanced at template concentration of 40 000 copies (approximately 1.36 pg). Validation was accomplished by analysing the same sample ten times to determine run variation and several samples for each species to determine between-sample variation. Twenty-eight additional mammalian species were reacted with the multiplex. The multiplex provides, for the first time, a definitive method for identification of species in a forensic context.     

Two-Dimensional Numerical Modeling of Direct-Current Electric Arcs in Nonequilibrium

A numerical model has been developed to analyze arc-anode attachment in direct-current electric arcs. The developed model fully couples a plasma flow with electromagnetic fields in a self-consistent manner. Electrons and heavy species are assumed to have different temperatures. Species continuities are taken into account to address the chemical nonequilibrium with the Self-Consistent Effective Binary Diffusion (SCEBD) formulation. Electric and magnetic field equations are determined with a newly developed Ohm’s law, an improvement over the conventional generalized Ohm’s law. The governing equations are discretized and solved using the Finite Volume Method (FVM) and Gauss–Seidel Line Relaxation (GSLR) method in a two-dimensional domain. The model is applied to a two-dimensional axisymmetric high-intensity argon arc. The results are compared favorably with experimental and other numerical data. A significant electric potential drop has been observed in the vicinity of the anode due to the thermal and chemical nonequilibrium effects.     

Identification of five <Emphasis Type="Italic">Listeria</Emphasis> species based on infrared spectra (FTIR) using macrosamples is superior to a microsample approach

Microorganisms can be identified using both macrosamples and microsamples based on infrared spectra (FTIR). This work compares the identification of the five closely related Listeria species L. innocua, L. ivanovii, L. monocytogenes, L. seeligeri, and L. welshimeri using both methods. The overall identification success for 25 strains was 92.8% for the former and 79.2% for the latter methods, respectively. The worst performances of the microsample method were obtained for L. innocua, L. ivanovii, and L. monocytogenes, while L. seeligeri and L. welshimeri did not show significant differences between the techniques. Identification success was mainly influenced by the age of the cells and the spatial heterogeneity of the microcolonies, as analyzed by the microsample method. Spectra of Listeria cells near the stationary phase exhibited more species-specific markers and thus allowed for better discrimination than spectra of growing cells. Furthermore, the heterogeneity of cell composition at different locations in microcolonies of L. innocua, L. ivanovii and L. monocytogenes resulted in limited discrimination success of the microsample method. We conclude that, at least in the case of Listeria, the macrosample method is superior to the microsample method, although the latter is the faster technique.     

Two-Step Redox in Polyimide: Witness by In Situ Electron Paramagnetic Resonance in Lithium-ion Batteries

Organic materials are promising candidates for future rechargeable batteries, owing to their high natural abundance and rapidly redox reaction. Elaborating the charge/discharge process of organic electrode is critical to unveil the fundamental redox mechanism of lithium-ion batteries (LIBs), but monitoring of this process is still challenging. Here, we report a nondestructive electron paramagnetic resonance (EPR) technique to real-time detect the electron migration step within polyimide cathode. From in situ EPR tests, we vividly observe a classical redox reaction along with two-electron transfer which only shows one pair of peaks in the cyclic voltammetry curve. The radical anion and dianion intermediates are detailed delineation at redox sites in EPR spectra, which can be further confirmed through density functional theory calculations. This approach is especially crucial to elaborate the correlation behind electrochemical and molecular structure for multistep organic-based LIBs.     

Synergistic Activation of Nitrite and Thiocarbonyl Compounds Affords NO and Sulfane Sulfur via (Per)thionitrite (SNO−/SSNO−)

(Per)thionitrite (SNO⁻/SSNO⁻) intermediates play vital roles in modulating nitric oxide (NO) and hydrogen sulfide (H₂S) dependent bio-signalling processes. Whilst the previous preparations of such intermediates involved reactive H₂S/HS⁻ or sulfane sulfur (S⁰) species, the present report reveals that relatively stable thiocarbonyl compounds (such as carbon disulfide (CS₂), thiocarbamate, thioacetic acid, and thioacetate) react with nitrite anion to yield SNO⁻/SSNO⁻. For instance, the reaction of CS₂ and nitrite anion (NO₂⁻) under ambient condition affords CO₂ and SNO⁻/SSNO⁻. A detailed investigation involving UV/Vis, FTIR, HRMS, and multinuclear NMR studies confirm the formation of SNO⁻/SSNO⁻, which are proposed to form through an initial nucleophilic attack by nitrite anion followed by a transnitrosation step. Notably, reactions of CS₂ and nitrite in the presence of thiol RSH show the formation of organic polysulfides R-S_n-R, thereby illustrating that the thiocarbonyls are capable of influencing the pool of bioavailable sulfane sulfurs. Furthermore, the availability of both NO₂⁻ and thiocarbonyl motifs in the biological context hints at their synergistic metal-free activations leading to the generation of NO gas and various reactive sulfur species via SNO⁻/SSNO⁻.     

Guaiacol as an Organic Superoxide Dismutase Mimics for Anti-ageing a Ru-based Li-rich Layered Oxide Cathode

High-capacity Li-rich layered oxides using oxygen redox as well as transition metal redox suffer from its structural instability due to lattice oxygen escaped from its structure during oxygen redox and the following electrolyte decomposition by the reactive oxygen species. Herein, we rescued a Li-rich layered oxide based on 4d transition metal by employing an organic superoxide dismutase mimics as a homogeneous electrolyte additive. Guaiacol scavenged superoxide radicals via dismutation or disproportionation to convert two superoxide molecules to peroxide and dioxygen after absorbing lithium superoxide on its partially negative oxygen of methoxy and hydroxyl groups. Additionally, guaiacol was decomposed to form a thin and stable cathode-electrolyte interphase (CEI) layer, endowing the cathode with the interfacial stability.     

Stable Operation of Aqueous Organic Redox Flow Batteries in Air Atmosphere

As a green route for large-scale energy storage, aqueous organic redox flow batteries (AORFBs) are attracting extensive attention. However, most of the reported AORFBs were operated in an inert atmosphere. Herein, we clarify this issue by using the reported AORFB (i.e., 3, 3′-(9,10-anthraquinone-diyl)bis(3-methylbutanoicacid) (DPivOHAQ)||Ferrocyanide) as an example. We demonstrate that the dissolved O₂ can oxidize the discharged DPivOHAQ in anolyte, leading to capacity-imbalance between anolyte and catholyte. Therefore, this cell shows continuous capacity fading when operated in an air atmosphere. We propose a simple strategy for this challenge, in which the oxygen evolution reaction (OER) in catholyte is employed to balance oxygen reduction reaction (ORR) in anolyte. When using the Ni(OH)₂-modifed carbon felt (CF) as a current collector for catholyte, this cell shows an excellent stability in air atmosphere because the Ni(OH)₂-induced OER capacity in catholyte exactly balances the ORR capacity in anolyte. Such O₂-balance strategy facilitates AORFBs’ practical application.