保健食品中非法添加物检测的前处理及分析方法研究进展

保健食品作为一种特定的食品种类,能调节人体的机能,适用于特定人群食用.但是在保健食品中添加化学药物和非法添加物的现象也层出不穷,因此迫切需要建立多指标的有效检测方法,为保健食品的质量安全提供技术保障.高效的前处理方法和高灵敏的分析方法为检测非法添加物提供了有效的技术手段.综述了近三年来溶剂萃取和固相萃取样品前处理方法,以及高效液相色谱、实时直接分析质谱、表面增强拉曼光谱及色谱-质谱串联技术等分析方法在微量及痕量非法添加物检测中的应用,为进一步研究建立高效简便的前处理方法和检测新方法、新技术提供理论参考.     

Regulation of Cathode‐Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries

As the power supply of the prosperous new energy products, advanced lithium ion batteries (LIBs) are widely applied to portable energy equipment and large‐scale energy storage systems. To broaden the applicable range, considerable endeavours have been devoted towards improving the energy and power density of LIBs. However, the side reaction caused by the close contact between the electrode (particularly the cathode) and the electrolyte leads to capacity decay and structural degradation, which is a tricky problem to be solved. In order to overcome this obstacle, the researchers focused their attention on electrolyte additives. By adding additives to the electrolyte, the construction of a stable cathode‐electrolyte interphase (CEI) between the cathode and the electrolyte has been proven to competently elevate the overall electrochemical performance of LIBs. However, how to choose electrolyte additives that match different cathode systems ideally to achieve stable CEI layer construction and high‐performance LIBs is still in the stage of repeated experiments and exploration. This article specifically introduces the working mechanism of diverse electrolyte additives for forming a stable CEI layer and summarizes the latest research progress in the application of electrolyte additives for LIBs with diverse cathode materials. Finally, we tentatively set forth recommendations on the screening and customization of ideal additives required for the construction of robust CEI layer in LIBs. We believe this minireview will have a certain reference value for the design and construction of stable CEI layer to realize desirable performance of LIBs.     

Modulating the Enantiodiscrimination Features of Inherently Chiral Selectors by Molecular Design: A HPLC and Voltammetry Study Case with Atropisomeric 2,2’-Biindole-Based Monomers and Oligomer Films

A family of inherently chiral electroactive selectors based on the 2,2’-biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios.     

Azoalkanes—novel flame retardants and their structure–property relationship

A number of symmetrical and unsymmetrical azoalkanes of the general formula R′?N = N?R and related azoxy, hydrazone as well as azine derivatives have been synthesized in order to assess their potential as novel flame retardants for polypropylene alone or in combination with commercially available flame retardants such as alumina trihydrate (ATH), decabromodiphenyl ether (DecaBDE) and tris(3‐bromo‐2,2‐bis(bromomethyl)‐propyl)phosphate (TBBPP). The experimental results show that in the series of different sized azocycloalkanes the flame retardant efficacy decreased in the following order: R = cyclohexyl > cyclopentyl > cyclobutyl > cyclooctanyl >> cyclododecanyl. Whereas in the series of aliphatic azoalkanes compounds the efficacy decreased in the following order: R = n‐alkyl > tert‐butyl > tert‐octyl. In addition, also some of the prepared azoxy, azine, and hydrazone derivatives provide flame retardancy to polypropylene films at already very low concentrations (0.25–1 wt%). Noteworthy is that in contrast to other halogen‐free radical generators, the azoalkanes are also very effective as flame retardants in polypropylene thick moldings. Interestingly, it was found that 4,4′‐bis(cyclohexylazocyclohexyl)‐methane) shows a strong synergistic effect with ATH. Thus, in the presence of 0.5 wt% of azoalkane the ATH loading could be reduced from 60 to 25 wt% and still UL94 V‐2 rating could be reached. Furthermore, the fire testing data reveal that azoalkanes show a synergistic effect with DecaBDE and when used in conjunction with very low loadings of TBBPP. Copyright © 2010 John Wiley & Sons, Ltd.     

The spreading behaviour of perfluoropolyether droplets on solid surfaces

The spread of perfluoropolyether （PFPE） droplets on solid surfaces has been measured from the top-down view through a microscope system. Effects of substrates, molecular weight and end-group functionality on spreading of the PFPE droplets have been studied experimentally and the results were compared with those by molecular dynamics （MD） simulations. Silicon wafer and diamond-like carbon （DLC） substrates were used to study the effect of substrates on spreading. Two types of PFPE, Z-dol and Z-tetraol, with the same chain structure and various molecular weights （2000 and 4000 g/mol） were employed in experiments. Effect of molecular weight has been investigated through comparing the spreading of Z-dol 2000 and Z-dol 4000, and it is found that the increase of molecular weight will decrease the mobility of PFPE. Comparison between spreading of Z-dol and Z-tetraol of the same molecular weight proved that functional end group plays a significant role on the spreading of PFPE, which confirmed the MD simulation results.     

ON THE MECHANISM OF “HYDROPHOBIC” INTERACTIONS

It is shown that the interfacial attraction between low-energy bodies immersed in aqueous media, known as “hydrophobic” interaction, can be quantitatively accounted for by, mainly, the hydrogen-bonding energy of cohesion of water, plus, to a very minor extent, a van der Waals-Lifshitz attraction between the Immersed law-energy bodies.     

Comparison of Bottom-up Filling in Electroless Plating with an Addition of PEG,PPG and EPE

The bottom‐up filling capabilities of electroless copper plating bath with an addition of additives, such as polyethylene glycol (PEG), polypropylene glycol (PPG) and triblock copolymers of PEG and PPG with ethylene oxide terminal blocks termed EPE, were investigated by the cross‐sectional scanning electron microscopy (SEM) observation of sub‐micrometer trenches. Though three additives had inhibition for electroless copper deposition, the suppression degrees of three additives were different. EPE‐2000 had the strongest suppression for electroless copper deposition, and the suppression of PEG‐2000 was the weakest. The bottom‐up filling capability of electroless copper was investigated in a plating bath containing different additives with the concentration of 2.0 mg/L. The cross‐sectional SEM observation indicated the trenches with the width of 280 nm and the depth of 475 nm were all completely filled by the plating bath with an addition of EPE‐2000, but the trenches were not completely filled by the plating bath with an addition of PEG‐2000 or PPG‐2000, and some voids appeared. Linear sweep voltammetry measurement indicated that three additives all inhibited the cathodic reduction reaction and the anodic oxidation reaction, and the inhibition of EPE‐2000 was the strongest among three additives, which agreed with that of the deposition rate of electroless copper. Significant differences in surface roughness of deposited copper film were observed by UV‐visible near‐infrared for different suppressors, and the bright and smooth of deposited copper film were in accordance with the inhibition of three additives.     

Microstructure and morphology of self‐assembling multiblock poly(ethylene‐1‐butene)‐n copolymers in solution studied by wide‐Q small‐angle neutron scattering and microscopy

Multiblock ethylene‐1‐butene copolymers (PEB‐n) with graded ethylene content (where n is the number of ethyl branches per 100 backbone carbons) represent efficient cold filter plugging point (CFPP) depressants for crude oils and middle distillates. The aggregation behavior and the interaction with wax molecules of a tetrablock PEB‐2.6/PEB‐6.0/PEB‐10.9/PEB‐13.2 and triblock PEB‐6.5/PEB‐8.9/PEB‐10.1 copolymers in decane solutions were investigated over a wide temperature range by combining different small‐angle neutron scattering techniques and optical microscopy. The experimental results revealed in the decrease of temperature formation and evolution of multisized structural levels showing a hierarchical organization on the length scale from 1 nm up to 10 μm. One‐dimensional polymer aggregates arising as initial structures associate and branch that lead to the occurrence of complex macroaggregates with diffusive interfaces and sizes of several microns. The one‐dimensional copolymer structure shows longitudinal density modulation and micellar‐like substructures in neat polymer solutions. When wax is added, this structure becomes more homogeneous in decrease of temperature as a consequence of the cocrystallization of wax and copolymer. The wax crystallization in board‐like objects of much smaller size than required by the CFPP criterion of oil and refinery industry (filter mesh size of 45 μm) is templated and controlled by the assembling features of the crystalline–amorphous PEB‐n multiblock copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Multielement determination of major elements in polymer additives by microwave induced plasma atomic emission spectrometry after microwave digestion

A method for multielement determination of major elements in polymer additives by microwave induced plasma atomic emission spectrometry (MIP-AES) has been elaborated. Microwave digestion with nitric acid was selected for sample preparation because of its speed and versatility. Sodium nitrate was added to the digestion mixture in order to reduce phosphorus losses. The precision obtained varied between 2 and 4.5% depending on the element determined. The accuracy of the method was studied by analyzing the Spex 5-element oil standard. The method was applied to a variety of commercial and in-house prepared compositions.     

Pressure distribution in a porous squeeze film bearing lubricated by a Vočadlo fluid

The influence of a wall porosity on the pressure distribution in a curvilinear squeeze film bearing lubricated by a lubricant being a viscoplastic fluid of a Vo?adlo type is considered.