Fermentation characteristics and the dynamic trend of chemical components during fermentation of Massa Medicata Fermentata

As a representative of traditionally fermented Chinese medicine, Massa Medicata Fermentata (MMF) shows the functions of invigorating the spleen and stomach and promoting digestion, which plays an important role in the treatment of gastrointestinal diseases. The fermentation mechanism and the key factors that affect the quality of MMF have not been revealed yet, which has become an urgent issue that limits its clinical application. This article aims to systematically and comprehensively reveal the transformation of physical properties and the dynamic trend of chemical components including substrate components, volatile components, and lactic acid as anaerobic fermentation product during MMF fermentation. Along with obvious hyphae growth observed for MMF, the weight of MMF decreased, and the moisture and temperature increased. Through the quantified 14 components from substrate, ferulic acid increased from 45.53 ± 6.94 to 141.89 ± 78.40 μg/g, while glycosides and phenolic acids declined except caffeic acid. Also, within the 66 volatile components analyzed, alcohols and acids increased, while aldehydes and ketones decreased. Lactic acid was not detected in the fermentation substrate, but an apparent increase in lactic acid content was observed along with the increased fermentation days, resulting in 2.54 ± 0.15 mg/g on day 8. Based on the tested components, the fermentation process of MMF was discriminated into three distinct stages by principal component analysis, and an optimal fermentation time of four days was proposed. The results of this study will be of great significance to clarify the characteristics of fermentation and conduce to improving quality standards of MMF.     

Fast simultaneous determination of 23 veterinary drug residues in fish,poultry, and red meat by liquid chromatography/tandem mass spectrometry

The misuses of veterinary drugs can result in the accumulation of residues in food of animal origin that can make its way to the final consumer. Herein we describe a simple method for the accurate determination of beta-lactams, quinolones, sulphonamides, and tetracyclines in fish, poultry, and red meat. No extraction cartridges were used; instead, the extraction process consisted of the addition of an organic solvents, shaking, centrifugation, and dilution. An extensive validation process demonstrated an excellent linearity (R² ≥ 0.99) for 23-drug residues. The recovery of drugs in different matrices at two concentration levels (n = 6) was in the range of 82–119%. The method was proved to be repeatable and reproducible with intra/inter-day measurements (RSDs lower than 20%). The quantification limits of drug residues were in the range of 0.8 to 45.3 ug/kg, which is well below the maximum residue limits set by most regulatory authorities. This method was successfully applied to the routine analysis of 20 fish, poultry, and red meat samples (n = 60).     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

交替三线性分解算法与反相高效液相-二极管阵列检测方法相结合同时测定苯二酚的位置异构体

 利用交替三线性分解算法与反相高效液相 二极管阵列检测 (RP HPLC DAD)相结合 ,在洗脱时间为1 0 86min～ 1 399min(间隔 1 / 1 50min)、紫外吸收波长为 2 68nm～ 2 98nm(间隔 1nm)时对苯二酚位置异构体的重叠及光谱体系进行了分辨研究。分辨结果与实际结果一致。同时测定了水溶液中共存的邻苯二酚、间苯二酚和对苯二酚的含量 ,回收率分别为 (1 0 0 1± 1 0 ) % ,(99 4± 1 4) % ,(1 0 0 5± 1 7) %。研究结果表明 :该方法定量快速准确 ,实验操作步骤简单 ,解决了在干扰物存在条件下三者很难同时分辨的问题。     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

Analysis of basic hair dyes by HPLC with on-line post-column photochemical derivatisation

Summary A reversed phase liquid chromatographic method is proposed for the analysis of basic hair dyes (raw materials and colourant formulations). The performance of the method was enhanced by introducing post-column on-line photochemical derivatisation in combination with a Diode Array Detector. On-line photoderivatisation provided an effective way of selectively transforming the analytes to compounds with different spectral properties. For each analyte two characteristic UV-Visible spectra (photoreactor on and off) were obtained with the same mobile phase and this information in combination with the chromatographic data (k' at pH 3.0 and 4.5) enabled the unambiguous identification of both commonly used, approved, and banned basic hair dyes. Additionally, this approach was found useful to improve the method sensitivity, allowing the determination of analytes present in low concentration (0.03%) in complex commercial formulations.This work constitutes part of the thesis for the Dottorato di Ricerche of Roberto Gotti.     

Electrooxidation Mechanism of Methanol at Pt-Ru Catalyst Modified GC Electrode in Electrolytes with Different pH Using Electrochemical and SERS Techniques

The electrochemical and in-situ surface-enhanced Raman spectroscopy （SERS） techniques were used to investigate the electrooxidation behavior of methanol in acidic, neutral and alkaline media at a Pt-Ru nanoparticle modified glassy carbon （Pt-Ru/GC） electrode. The results showed that methanol could be dissociated spontaneously at the Pt-Ru/GC electrode to produce a strongly adsorbed intermediate, CO. It was found that CO could be oxidized more easily in the alkaline medium than in the acidic and neutral media. The peak potential of methanol oxidation was shifted from 0.663 and 0.708 V in the acidic and neutral media to -0.030 V in the alkaline medium, which is due to that the adsorption strength of CO on the Pt surface in the alkaline medium is weaker than that in the acidic and neutral media. The final product of the methanol oxidation is CO2. However, in the alkaline medium, CO2 produced would form CO3^2- and HCO3^- resulting in the decrease in the alkaline concentration and then in the decrease in the performance of DMFC. Therefore, the performance of the alkaline DMFC is not Stable.     

Norvancomycin-capped silver nanoparticles: Synthesis and antibacterial activities against E. coli

The synthesis of norvancomycin (NVan)-capped silver nanoparticles (Ag@NVan) and their notable in vitro antibacterial activities against E. coli, a Gram-negative bacterial strain (GNB), are reported here. Mercaptoacetic acid-stabilized spherical silver nanoparticles with a diameter of 16±4 nm are prepared by a simple chemical reaction. The formation process of the silver nanoparticles is investigated by UV-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). NVan is then grafted to the terminal carboxyl of the mercaptoacetic acid in the presence of N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDAC). The TEM images of single bacteria treated with Ag@NVan show that plenty of Ag@NVan aggregate in the cell wall of E. coli. A possible antibacterial mechanism is proposed that silver nanoparticles may help destroy the stability of the outer membrane of E. coli, which makes NVan easier to bind to the nether part of the peptidoglycan structure. The antibacterial activities of silver nanoparticles on their own, together with the rigid polyvalent interaction between Ag@NVan and cell wall, enables Ag@NVan to be an effective inhibitor of GNB. This kind of bionanocomposites might be used as novel bactericidal materials and we also provide an effective synthesis method for preparing functional bioconjugated nanoparticles here. Supported by the National Natural Science Foundation of China (Grant No. 50373036) and Fok Ying Tung Education Foundation (Grant No. J20040212)     

亮氨酸与异亮氨酸在金/银核-壳复合纳米粒子上的吸附状态

The Raman spectra and Surface enhanced Raman spectra (SERS) of leucine and isoleucine adsorbed on core-shell Au/Ag nanoparticles were obtained and assigned, and the different Raman peaks resulting from different vibrational models of the isomers忆groups were analysed. In Raman spectra, the leucine’s (ω(CH3)) is at 962, 945, 924 cm-1, (δas(CH3)) at 1408, 1454 cm-1; corresponding values for isoleucine are, 922 cm-1 and 1448, 1420, 1394 cm-1, respectwely. The difference in the peak positions of corresponding groups between leucine and isoleucine is more apparent in the SERS at acidic and basic conditions. The relationship between leucine and isoleucine’s concentration and SERS was interpreted preliminarily and the adsorption model on the core-shell Au/Ag nanoparticle surface was speculated.     

An analysis of avidin, biotin and their interaction at attomole levels by voltammetric and chromatographic techniques

The electroanalytical determination of avidin in solution, in a carbon paste, and in a transgenic maize extract was performed in acidic medium at a carbon paste electrode (CPE). The oxidative voltammetric signal resulting from the presence of tyrosine and tryptophan in avidin was observed using square-wave voltammetry. The process could be used to determine avidin concentrations up to 3 fM (100 amol in 3 l drop) in solution, 700 fM (174 fmol in 250 l solution) in an avidin-modified electrode, and 174 nM in a maize seed extract. In the case of the avidin-modified CPE, several parameters were studied in order to optimize the measurements, such as electrode accumulation time, composition of the avidin-modified CPE, and the elution time of avidin. In addition, the avidin-modified electrode was used to detect biotin in solution (the detection limit was 7.6 pmol in a 6 l drop) and to detect biotin in a pharmaceutical drug after various solvent extraction procedures. Comparable studies for the detection of biotin were developed using HPLC with diode array detection (HPLC-DAD) and flow injection analysis with electrochemical detection, which allowed biotin to be detected at levels as low as 614 pM and 6.6 nM, respectively. The effects of applied potential, acetonitrile content, and flow rate of the mobile phase on the FIA-ED signal were also studied.