Effect of Basic and Acidic Additives on the Separation of Some Basic Drug Enantiomers on Polysaccharide‐Based Chiral Columns With Acetonitrile as Mobile Phase

The separation of enantiomers of 16 basic drugs was studied using polysaccharide‐based chiral selectors and acetonitrile as mobile phase with emphasis on the role of basic and acidic additives on the separation and elution order of enantiomers. Out of the studied chiral selectors, amylose phenylcarbamate‐based ones more often showed a chiral recognition ability compared to cellulose phenylcarbamate derivatives. An interesting effect was observed with formic acid as additive on enantiomer resolution and enantiomer elution order for some basic drugs. Thus, for instance, the enantioseparation of several β‐blockers (atenolol, sotalol, toliprolol) improved not only by the addition of a more conventional basic additive to the mobile phase, but also by the addition of an acidic additive. Moreover, an opposite elution order of enantiomers was observed depending on the nature of the additive (basic or acidic) in the mobile phase. Chirality 27:228–234, 2015. © 2015 Wiley Periodicals, Inc.     

Interfacial electron transfer of glucose oxidase on poly(glutamic acid)-modified glassy carbon electrode and glucose sensing

The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5–5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose.     

Electrochemical study of the interaction between cytochrome c and DNA at a modified gold electrode

The direct electron transfer of surface-confined horse heart cytochrome c (Cyt c) was achieved using COOH-terminated alkanethiolate-modified gold electrode. Later DNA was immobilized on the two-layer modified electrode. The quantitative determination of DNA was explored and the interaction between cytochrome c and DNA was studied. The binding site sizes were determined to be 15 bp per Cyt c molecule with double-stranded (ds) DNA and 30 nucleotides binding one Cyt c molecule with single-stranded (ss) DNA. At the dsDNA/Cyt c/MUA/Au electrode, the rate constant of oxidation electron transfer k(s,ox)=1.59x10(-3)cms-1 was obtained, at the ssDNA/Cyt c/MUA/Au electrode, the value was 2.43x10(-3)ms-1 when the scan rate was 1.0V/s. The different electrodes were characterized with electrochemical quartz crystal microbalance and atomic force microscope.     

Precise blood lead analysis using a combined internal standard and standard addition approach with disposable screen-printed electrodes

We report here a highly accurate and efficient method for blood lead analysis (BLA) through the use of a disposable electrode. A new type of mercury-plated preanodized screen-printed carbon electrode, together with a thallium(III) internal standard, simplifies calibration and gives easily quantifiable signals for accurate BLA. A preanodization procedure improves the preconcentration ability of the working electrode through the effect of lead (Pb) complexing with an electrogenerated surface functional group, mainly >C=O. Under optimized conditions, the ratio of the anodic stripping peak currents of Pb and Tl (i.e., i(Pb)/i(Tl)) is linear against [Pb] in the window of 1-300 ppb with a correlation coefficient and detection limit (signal-to-noise ratio=3) of 0.999 and 0.23 ppb, respectively. This approach was used to analyze blood samples (n=55) from workers at a local battery factory. The results are consistent with those obtained from graphite furnace atomic absorption spectroscopy and confirm the applicability of the proposed method.     

Salicylate poly(vinyl chloride) membrane electrode based on (2-[(E)-2-(4-nitrophenyl) hydrazono]-1-phenyl-2-(2-quinolyl)-1-ethanone) Cu(II)

A new salicylate-selective electrode based on the complex of (2-[(E)-2-(4-nitrophenyl)hydrazono]-1-phenyl-2-(2-quinolyl)-1-ethanone) Cu(II) as the membrane carrier was developed. The electrode exhibited a good Nernstian slope of -59.6+/-1.0 mV/decade and a linear range of 1.0 x 10(-6) to 1.0M for salicylate. The limit of detection was 5.0 x 10(-7) M. The electrode had a fast response time of 10 s and can be used for more than 3 months. The selective coefficients were determined by the fixed interference method and could be used in the pH range of 4.0 to 10.5. The electrode was employed as an indicator electrode for direct determination of salicylate in pharmaceutical and biological samples.     

脂溶性维生素的安全性

脂溶性维生素是很重要的营养素,在食品或饲料业中作为添加剂,使用范围广泛。这类维生素可在体内贮存,缺乏或过量都会影响机体生长和代谢功能。本文综述脂溶性维生素的生理功能与来源、缺乏与过量时的危害,以及添加时的注意事项,以保证其使用的安全性。     

Application of Non-invasive Microsensing System to Simultaneously Measure Both H+ and O2 Fluxes Around the Pollen Tube

Various ionic and molecular activities in the extracellular environment are vital to plant cell physiological processes. A noninvasive microsensing system (NMS) based on either the scanning ion-selective electrode technique (SIET) or the scanning polarographic electrode technique (SPET) is able to obtain information regarding the transportation of various ions/molecules in intact samples under normal physiological conditions. The two-probe simultaneous test system (2STS) is an integrated system composed of SIET,SPET, and a Xu-Kunkel sampling protocol. In the present study, 2STS was able to simultaneously measure fluxes of H+ and O2 of the lily (Lilium Iongiflorum Thunb. cv. Ace) pollen tube while avoiding interference between the two probes. The results indicate that the proton fluxes were effluxes, whereas the oxygen fluxes were influxes, and they were closely correlated to each other surrounding the constitutive alkaline band region. Specifically, when the proton effluxes increased, the oxygen influxes also increased. Therefore,the hypothesis of condensed active mitochondria existing in the alkalized area of the pollen tube proposed by Hepler's group is supported.     

Vacuum foam drying for preservation of LaSota virus: Effect of additives

The purpose of this research was to apply vacuum foam drying (VFD) for processing of LaSota virus and to screen formulation additives for its stability. The aqueous dispersion of harvest containing sucrose or trehalose in combination with additive (monosaccharides, polymers, N-Z-amine) was prepared. The diluted dispersions in vials were vacuum concentrated, foamed to form a continuous structure, and vacuum dried. The products were evaluated for foam characteristics, residual moisture, virus titer, x-ray diffraction pattern, and stability profile. The foamability increased with solid content in solutions. The foamability of sucrose was enhanced with incorporation of N-Z-amine (10% and 15% wt/vol) and polyvinyl pyrrolidone (PVP K30, 3% wt/vol). The fructose- or galactose-containing mixtures were deposited irregularly on the vial surface. The virus titer increased with disaccharides in the formulation. Sucrose provided better protection than trehalose. Unlike lyophilization, N-Z-amine with sucrose protected the virus from Millard’s Browning. Amino acids do not have a catalytic effect on hydrolysis of sucrose during VFD. Monosaccharides were ineffective. A synergistic effect of PVP K30 or polyethylene glycol 6000 (3% wt/vol) with N-Z-amine provided the maximum virus titer (6.97 and 7.15, respectively). This formulation retained the desired virus potency at 5°, 25°, and 40°C. The diffraction pattern revealed that a threshold concentration of N-Z-amine was required for inhibiting crystallization of sucrose during VFD. VFD was successfully applied to produce a solid LaSota formulation. The products were amorphous and did not devitrify on storage. Published: July 21, 2006