Voltammetric Determination of Trace Amounts of 2‐Methyl‐4,6‐Dinitrophenol at a Silver Solid Amalgam Electrode

The voltammetric behavior of 2‐methyl‐4,6‐dinitrophenol was investigated by differential pulse voltammetry (DPV) at a nontoxic mercury meniscus‐modified silver solid amalgam electrode (m‐AgSAE). Conditions have been found for its determination by DPV at m‐AgSAE in the concentration range of 0.2 to 1 μmol L^?1.     

Radiation formation of polymeric nanogels

An alternative method of synthesis of polymeric nanogels is proposed, based not on polymerization, but on intramolecular crosslinking of polymer chains, initiated by pulse irradiation in dilute aqueous solutions. Kinetic data show that for many water-soluble polymers irradiation under these conditions result in intramolecular crosslinking. Preliminary product studies on poly(vinyl alcohol) indicate that in fact internally crosslinked macromolecules can be obtained by this technique.     

羟乙芦丁在玻碳电极上的阳极微分脉冲伏安法测定

本文对羟乙芦丁在玻碳电极上的阳极微分脉冲安行为进行了研究，发现在Ｎａ２ＨＰＯ４溶液中（ｐＨ＝８．９５）于＋０．６４Ｖ（ｖｓ．Ａｇ／ＡｇＣｌ）左右产生一个良好的阳极氧化伏安峰，浓度在５～６０ｍｇ／Ｌ之间与峰电流呈线性关系，不需分离直接测定了片剂中的羟乙芦丁含量。电极反应为扩散速率控制的不可逆可程。     

Induced Absorption of C60 and a Water-Soluble C60-Derivative in SiO2 Sol-Gel Matrices

Porous sol-gel glasses, either impregnated with pure C₆₀ or doped with a methanofullerene derivative, have been studied and induced absorption or reverse saturable absorption (RSA) has been observed in both types of solid materials. The samples impregnated by pure C₆₀ mainly contain well-dispersed fullerene molecules. Unlike crystalline films of C₆₀, their absorption dynamics can be well described by a 5-level model, developed for non-interacting C₆₀-molecules in solutions. Methanofullerene samples, on the other hand, show signs of micellar aggregation and therefore RSA dynamics that are influenced by solid state effects. We observe an important decrease of transmission at high fluences for both kinds of samples, a shortened singlet-state lifetime to that observed in solution, but nonetheless, a triplet yield, that cannot be considered as negligible. In the case of pure C₆₀ in a sol-gel matrix, we can explain the faster de-excitation dynamics, relative to behavior in solution, mainly by the absence of stabilizing aromatic solvents and also by the interaction of the amorphous environment with the molecules. Concerning the methanofullerene samples, the acceleration of the de-excitation dynamics can be principally attributed to solid-state effects due to the micellar aggregation.     

The electrocatalytic examination of cephalosporins at carbon paste electrode modified with CoSalophen

The electrocatalytic oxidation of cephalexin and cefazolin has been studied at a carbon paste electrode modified with cobalt salophen (CoSal) by cyclic voltammetry. The selectivity of the carbon paste modified with CoSal in detecting cephalexin and cefazolin was examined. To suggest the electrocatalytic mechanism for electro-oxidation of cefazolin, the electrochemical behavior of ceftriaxone was investigated which has a thiol group out of the beta lactam ring. The electrocatalytic oxidation of these antibiotics is shown to be irreversible at the CoSal modified electrode. Scan rate dependence of cefazolin, which is a sulfur-containing compound, has been examined. The results indicated that the electrocatalytic oxidation of the compounds is diffusion controlled. The responses of the modified electrode were compared with those of unmodified electrode and it has shown that the modified electrode has better sensitivity than unmodified electrode to the detection of cefazolin. The overall number of electrons contributed to the oxidation of cefazolin is obtained 1 by chronoamperometry; the number of electron involved in the rate-determining step was 1. The results of differential pulse voltammetry (DPV) using the modified electrode with high sensitivity were applied for the determination of cefazolin in human synthetic serum samples. The linear range was obtained from 1 × 10⁻⁵ to 1 × 10⁻³ M for DPV determination of cefazolin in buffered solutions (pH 3.0).     

Study of a Catalytic Mechanism in Additive Differential Pulse Techniques

The new electrochemical double pulse technique, known as additive differential normal pulse voltammetry (ADNPV) when there is no restriction on the duration of both pulses, and additive differential pulse voltammetry (ADPV) when t₂?t₁, has been applied to a pseudo‐first‐order catalytic mechanism. The expressions obtained here are applicable to planar and spherical electrodes, of any radius. This is of great interest since the size of the electrode plays an important role in the preponderating of diffusive and kinetics processes. The signal obtained with this technique presents the same morphological characteristics as the triple pulse technique, double differential pulse voltammetry (DDPV) and is more advantageous than DDPV and than the double pulse one, differential pulse voltammetry (DPV).     

二茂铁化学修饰电极测定丙二醛的研究

报道了在玻碳电极上共价键合二茂铁的新型化学修饰电极。研究了该电极对丙二醛的电催化作用。以微分脉冲伏安法测定丙二醛，方法具有较好的灵敏度和选择性。丙二醛的峰电流与其浓度在２０×１０－６～２０×１０－３ｍｏｌ／Ｌ呈良好的线性关系。     

Fractionation and purification of antioxidant peptides from Chinese sturgeon (Acipenser sinensis) protein hydrolysates prepared using papain and alcalase 2.4L

Protein hydrolysates have the potential to be natural and safer sources of bioactive peptides. In this study, two proteases were used to hydrolyze Chinese sturgeon (Acipenser sinensis) protein, and the hydrolysates were then purified to yield antioxidant peptides. The degree of hydrolysis of 23.56 % and 18.14 % was obtained using papain and alcalase 2.4L, respectivly, and hydrolysates had 96.80 % and 87.24 % total amino acid content, respectivly. The papain hydrolysate (PH) and alcalase 2.4L hydrolysate (AH) showed good antioxidant activity against DPPH^? (IC₅₀ of 3.64 and 3.15 mg/mL) and ABTS^?+ (IC₅₀ of 1.92 and 1.58 mg/mL), respectively. The low-molecular-weight (<1000 Da) fraction of both hydrolysates demonstrated the highest antiradical activity (IC₅₀ of 2.59 and 2.31 mg/mL, DPPH) and (IC₅₀ of 1.54 and 1.36 mg/mL, ABTS), respectively. Nine peptides were separated from both hydrolysates using reverse phase high performance liquid chromatography (RP-HPLC). The IC₅₀ for ABTS^?+ scavenging activity of peptide P5 with valine, glycine and asparagine (MW of 282.13 Da) from PH, and peptide P3 with histidine, glycine and alanine (MW of 302.74 Da) from AH was 0.89 and 0.72 mg/mL, respectively. The fractions and purified peptides obtained from Chinese sturgeon hydrolysates could be utilized as natural antioxidant substitutes in pharmaceuticals and food products.     

Effect of high-voltage pulses on electrochemical properties of a molten magnesium electrolyte

Effects of high-voltage pulses on electrochemical properties of a molten magnesium electrolyte is studied experimentally. It is established that the electroconductivity of the melt subjected to the pulses and the electrolysis current at a constant voltage increase by up to 25%. The relaxation time of nonequilibrium melt reaches a few tens of minutes and under certain conditions its dynamics is oscillatory.