Ionic liquid salt bridge based on tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide for stable liquid junction potentials in highly diluted aqueous electrolyte solutions

A moderately hydrophobic ionic liquid, tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide ([TBMOEP⁺][C₂C₂N⁻]), shows a very stable liquid junction potential upon contact with an aqueous solution whose ionic strength is as low as 1 μmol dm⁻³. The stability with the maximum excursion of the potential within ±0.5 mV for 30 min is very promising for accurate determination of pH and other single ion activities potentiometrically.     

船用pH计检定装置的研究

研制了船用pH计检定装置。以基准电压集成电路作为电压标准,以单片机为控制中心,组成船用pH计检定核心部分,控制船用pH计检定装置输出标准电位。检定装置的pH值输出范围:0～14.0000 pH;pH示值误差:0.0003 pH;电压输出范围:-1999.99～+1999.99 mV;电压分辨率:0.01 mV;温度补偿范围:0～99.9℃。     

Open tubular capillary electrochromatography: A useful microreactor for collagen I glycation and interaction studies with low-density lipoprotein particles

Diabetes, a multifunctional disease and a major cause of morbidity and mortality in the industrialized countries, strongly associates with the development and progression of atherosclerosis. One of the consequences of high level of glucose in the blood circulation is glycation of long-lived proteins, such as collagen I, the most abundant component of the extracellular matrix (ECM) in the arterial wall. Glycation is a long-lasting process that involves the reaction between a carbonyl group of the sugar and an amino group of the protein, usually a lysine residue. This reaction generates an Amadori product that may evolve in advanced glycation end products (AGEs). AGEs, as reactive molecules, can provoke cross-linking of collagen I fibrils. Since binding of low-density lipoproteins (LDLs) to the ECM of the inner layer of the arterial wall, the intima, has been implicated to be involved in the onset of the development of an atherosclerotic plaque, collagen modifications, which can affect the affinity of native and oxidized LDL for collagen I, can promote the entrapment of LDLs in the intima and accelerate the progression of atherosclerosis.In this study, open tubular capillary electrochromatography is proposed as a new microreactor to study in situ glycation of collagen I. The kinetics of glycation was first investigated in a fused silica collagen I-coated capillary. Dimethyl sulphoxide, injected as an electroosmotic flow marker, gave information about the charge of coating. Native and oxidized LDL, and selected peptide fragments from apolipoprotein B-100, the protein covering LDL particles, were injected as marker compounds to clarify the interactions between LDLs and the glycated collagen I coating. The method proposed is simple and inexpensive, since only small amounts of collagen and LDL are required. Atomic force microscopy images complemented our studies, highlighting the difference between unmodified and glycated collagen I surfaces.     

MEKC determination of IgG in human serum via a pH‐mediated acid stacking method

An on‐column preconcentration technique, pH‐mediated acid stacking, was used in this study to improve the sensitivity of MEKC‐UV analysis of IgG in human serum. Various parameters affecting pH‐mediated acid stacking were optimized systematically. To eliminate the matrix interferences of human serum and to combine the sample pretreatment procedure with the detection methodology, silica‐coated Fe₃O₄ magnetic nanoparticles modified with N‐(2‐aminoethyl)‐3‐aminopropyl‐trimethoxysilane were prepared and employed as solid phase extraction adsorbent to remove the abundant HSA from human serum. HSA was quantitatively removed by silica‐coated Fe₃O₄ magnetic nanoparticles modified with N‐(2‐aminoethyl)‐3‐aminopropyl‐trimethoxysilanes without retaining IgG at pH 9.3. Under the optimum conditions, the sensitivity of IgG was improved 40.3‐fold using a 100 s electrokinetic injection as compared with a 6 s hydrodynamic injection. The detection limit of IgG was found to be 0.1 mg/L, and the proposed method was successfully applied for the determination of IgG in human serum with satisfactory results.     

pH‐induced on–off switching of polycarbonate track‐etched membranes by plasma‐induced surface grafting

Surface functionalization of the plasma‐pretreated polycarbonate (PC) track‐etched membranes via plasma‐induced thermally graft copolymerization of acrylic acid (AAc) was carried out. The resulting PC membranes with grafted AAc side chains were characterized by X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG) analysis. The morphology of the PC membranes was studied by scanning electron microscopy (SEM). The results showed that the grafted PAAc polymers were formed uniformly inside the pores throughout the entire membrane thickness. With increase in the pore‐filling ratio, the pore diameters of PAAc‐grafted membranes became smaller. The PC‐g‐PAAc membranes exhibit rapid and reversible response of the flux to the environmental pH as pH is switched between 3 and 9. Between pH 3.5 and 5.5, the membranes demonstrate a pH‐valve function as the carboxyl group changes from neutral to charged with a corresponding variation in chain configuration. Copyright © 2009 John Wiley & Sons, Ltd.     

Dual crosslinked pH‐ and temperature‐sensitive hydrogel beads for intestine‐targeted controlled release

Novel drug‐loaded hydrogel beads for intestine‐targeted controlled release were developed by using pH‐ and temperature‐sensitive carboxymethyl chitosan‐graft‐poly(N,N‐diethylacrylamide) (CMCTS‐g‐PDEA) hydrogel as carriers and vitamin B₂ (VB₂) as a model drug. The hydrogel beads were prepared based on Ca²⁺ ionic crosslinking in acidic solution and formed dual crosslinked network structure. The structure of hydrogel and morphology of drug‐loaded beads were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The study about swelling characteristics of hydrogel beads indicated that the beads had obvious pH‐ and temperature‐sensitivity. In vitro release studies of drug‐loaded beads were carried out in pH 1.2 HCl buffer solution and pH 7.4 phosphate buffer solution at 37°C, respectively. The results indicated that the dual crosslinked method could effectively control the drug release rate under gastrointestinal tract (GIT) conditions, which was superior to traditional single crosslinked beads. In addition, the effects of grafting percentage, pH value, and temperature on the release behavior of the VB₂ were investigated. The drug release mechanism of CMCTS‐g‐PDEA drug‐loaded beads was analyzed by Peppa's potential equation. According to this study, the dual crosslinked hydrogel beads based on CMCTS‐g‐PDEA could serve as suitable candidate for drug site‐specific carrier in intestine. Copyright © 2009 John Wiley & Sons, Ltd.     

Cu(L-His)2溶液配位结构的X射线吸收精细结构分析

采用X射线吸收精细结构分析(XAFS)方法分析Cu(His)₂复合物的配位模式,通过测定不同pH值下的铜的K边XAFS吸收谱,研究Cu(His)₂第一配位壳层的结构．为了更准确地验证Cu(His)₂配位结构,对组氨酸的羧基和咪唑分别进行了化学修饰．研究结果明确了在不同pH环境下组氨酸的羧基、氨基和咪唑的配位情况．对于争议最大的在生理pH值下组氨酸的配位方式,其结果更支持六配位模式,同时可能有少量的五配位模式配合物平衡存在.     

Growth and magnetic properties of single crystalline Ni nanowire arrays prepared by pulse DC electrodeposition

Highly textured Ni nanowire arrays were fabricated into anodic aluminum oxide(AAO) templates by pulse DC electrodeposition.The applied voltage and pH value of electrolytes were found strongly affecting the microstructure and magnetic properties of Ni nanowire arrays.Low applied potential and pH value both prefer to form polycrystalline fcc Ni nanowires.Increasing the applied potential or pH value favors the Ni [220] texture and even eventually forms the [220] oriented single crystal Ni wires,while exorbitan...     

赤铁矿和三羟铝石吸附Cu~(2+)的红外光谱研究

应用红外光谱法,研究了不同pH值和Cu2+浓度条件下,合成赤铁矿和三羟铝石吸附Cu2+后表面羟基结构及其特征吸收峰的变化。结果表明:(1)随Cu2+浓度增加,赤铁矿表面H—O—H和OH的变形振动参与了吸附反应,Cu2+强烈地缔结在Fe—O上,形成了Fe—O—(Cu)结构。(2)酸性条件下,H+破坏了赤铁矿表面的O—H结构,NO3-促使弱峰1 131 cm-1的产生。随pH值增大,赤铁矿表面OH-逐渐由伸缩振动转变为变形振动,Fe—OH和Fe3+—O2-结构不断发生改变。(3)三羟铝石对Cu2+的吸附发生在高波位,随Cu2+浓度增大,其表面游离羟基的O—H弯曲振动、水分子的OH-伸缩振动和H—O—H弯曲振动均参与了吸附反应,Al—O基中的Al3+渐被Cu2+取代从而加强了较低波位的振动强度。(4)随pH值增加,三羟铝石Al—OH的弯曲振动和Al—O的伸缩振动逐渐发生着改变,表明吸附Cu2+后,在其表面形成了AlOCu+与AlOCuOH结构。