Voltammetric Determination of Trace Amounts of Fenitrothion on a Novel Nano-TiO2 Polymer Film Electrode

A novel nano-TiO₂ polymer modified glassy carbon (GC) electrode was developed for the determination of an organophosphorous pesticide, fenitrothion (-NO₂), in citrate buffer solution. The electrochemical behavior of fenitrothion was characterized by using cyclic voltammetry. An irreversible form, -NO₂, was transformed into a reversible redox couple (-NHOH/-NO), and it can be used to determine trace fenitrothion by square wave voltammetry. The experimental parameters, such as film thickness, pH value, accumulation potential and time were optimized. Interestingly, a cyclic voltammetric scan was observed to be more effective than a constant potential for the accumulation of fenitrothion. A linear response over a fenitrothion concentration of 2.5×10^–8 to 1.0×10^–5M was exhibited, with a detection limit of 1.0×10^–8M (S/N=3). The high sensitivity and selectivity of this film electrode was demonstrated by its practical application to the determination of trace amounts of fenitrothion in lake water and apple samples.     

聚L-谷氨酸修饰电极的制备及对多巴胺的测定

用循环伏安法制备了聚L-谷氨酸修饰玻碳电极,研究了多巴胺在聚L-谷氨酸修饰电极上的电化学行为,建立了测定多巴胺的新方法。在pH 7.5的磷酸盐缓冲溶液中,用循环伏安法测定多巴胺的线性范围为1.0×10-4~4.0×10-8mol.L-1,检出限为5.0×10-9mol.L-1。该法用于药剂中多巴胺的测定,结果满意。     

Effect of Mineral Salts on Steady Rheological Properties of Nonionic Hydrophobically Modified Polyacrylamide and Its Stress-Relaxation Behavior

A micelle-forming polymerizable surfactant monomer, octylphenol polyoxyethylene acrylate (OP-10-AC), was synthesized, and then OP-10-AC was copolymerized with acrylamide (AM) to form nonionic hydrophobically modified polyacrylamide P(AM/OP-10-AC) through micellar copolymerization. In the absence of surfactants, it was investigated in detail that the effect of mineral salts and temperature on steady rheological properties of P(AM/OP-10-AC) solutions and the effect of concentrations on reduced viscosity of P(AM/OP-10-AC) in a dilute solution. The results indicate that concentrations of the copolymer, mineral salts and temperature had a strong influence on shear viscosity of P(AM/OP-10-AC) solutions, and the trend of reduced viscosity of P(AM/OP-10-AC) solutions was distinctly different from polyacrylamide with increasing concentrations of testing solutions. In addition, it was also investigated that stress-relaxation behavior of an aqueous solution of P(AM/OP-10-AC)/KCl. As a result, a stress-relaxation model of the copolymer solutions was proposed, which can further verify the correctness of the conclusion on stress-relaxation behavior of hydrophobic association hydrogels in the paper reported previously.     

Sol-gel-derived prussian blue-silicate amperometric glucose biosensor

A new type of inorganic biosensor is introduced. The sensor comprises glucose oxidase enzymes encapsulated in a sol-gel-derived Prussian blue-silicate hybrid network. Glucose is detected by the biocatalytic reduction of oxygen followed by catalytic reduction of hydrogen peroxide by the Prusian blue catalyst. The sol-gel silicate entails a rigid encapsulating matrix, the Prussian blue provides chemical catalysis and charge mediation from the reduction site to the supporting electrode, and the enzyme is responsible for the biocatalysis. The feasibility of a dual optical/electrochemical mode of analysis is also demonstrated.     

Animal bone meal as an efficient catalyst for crossed-aldol condensation

α,α′-Bis(substituted benzylidene)cycloalkanones were efficiently prepared from cycloalkanones and benzaldehydes in water by using animal bone meal (ABM) or ABM modified as a catalyst. It is shown that ABM modified can be quantitatively recovered and be reused effectively for many times. A comparison of catalytic activity of these catalysts is discussed.     

Mechanism of electrochemical reactions of polyaniline films formed under the conditions of cathodic oxygen reduction

Polyaniline films (further, CPANI) were obtained under the conditions of oxygen cathodic reduction in the aniline-containing solution on the electrodes of mixed indium tin oxide (ITO), graphite, and gold. CPANI films are characterized by redox processes in the potential ranges of 0.1–0.2 V and ～0.4 V (SCE). These processes are caused by the polymer chain fragments of different structure and the ratio between the peaks corresponding to these processes varies significantly as dependent on the synthesis conditions (electrode material, stirring, etc). The mechanism of electrode processes on CPANI is studied using the methods of cyclic voltammetry and quartz microgravimetry. It is found that only hydrogen cations and supporting electrolyte anions participate in the electrode process at the potentials of 0.1–0.2 V. The mechanism of redox processes on the obtained polymer films is discussed.     

Sensitive Adsorption Stripping Voltammetric Determination of Reserpine by a Glassy Carbon Electrode Modified with Multi-Wall Carbon Nanotubes

Adsorption stripping voltammetry, a very sensitive electroanalytical method, was employed to determine reserpine, a kind of anti-hypertensive drug. In 0.1M phosphate buffer with a pH of 6.0, reserpine was accumulated at a multi-wall carbon nanotubes (MWNT)-modified glassy carbon electrode (GCE) surface under the condition of open-circuit. In the following anodic sweep from 0.20 to 1.00V, reserpine, adsorbed at the MWNT-modified GCE surface, was oxidized and yielded a sensitive oxidation peak at 0.64V. Due to its unique structure and extraordinary properties, MWNT shows a ten times higher accumulation efficiency toward reserpine, compared with a bare GCE. Hence, the amount of reserpine at the MWNT-modified GCE surface increases significantly, and finally the oxidation peak current improves greatly. The experimental conditions, such as supporting electrolyte, pH value, the amount of MWNT-DHP suspension, accumulation time and scan rate, were optimized for the measurement of reserpine, and a sensitive electroanalytical method was proposed for reserpine determination. The oxidation peak current varies linearly with the concentration of reserpine over the range of 2×10^–8 to 1×10^–5M, and the detection limit is 7.5×10^–9M after 4min open-circuit accumulation. The relative standard deviation at 1×10^–6M reserpine was about 4.7% (n=7), indicating excellent reproducibility. This new method was successfully demonstrated with reserpine injections and tablets.     

Applications of surfactant-modified clays to synthetic organic chemistry

Two triphase catalysts (SLL) have been developed for organic phase-aqueous phase reactions catalyzed by suitable modified clay (solid phase). These triphase catalysts have been applied to nucleophilic displacement on activated (benzylic) as well as unactivated organic halides and provide a convenient and effective method of preparation of the corresponding products. Other useful transformations to, which these triphase catalysts have been successfully applied are the synthesis of 9,9-dichloro bicyclo[6.1.0]nonane, O-alkylation and C-alkylation of β-naphthol.     

羧甲基多糖的免疫调节作用

介绍了羧甲基淀粉,羧甲基茯苓多糖和羧甲基变性半纤维素等的免疫调节作用。可增加免疫细胞的活性和应答能力,增加免疫细胞的数量,并促进细胞因子的生成。通过增加机体的免疫功能发挥抗肿瘤作用,又不损害正常细胞。     

Swelling of hydrophobically modified poly(acrylamide) and poly(acrylamide)-co-(acrylic acid) gels in surfactant solutions

A series of hydrophobically modified polyacrylamide and polyacrylamide-co-poly(acrylic acid) gels with systematically varying hydrophobicity were prepared by free-radical polymerization of acrylamide, n-alkylacrylamides (n = 10, 12, and 14), and acrylic acid. The swelling of these gels was examined in water and in both anionic and cationic surfactant solutions. It was found that the gels which incorporated acrylic acid showed extremely high swelling in water. Maximum swelling was observed in gels which incorporated 10 mol% acrylic acid. The swelling of these gels was much less in solutions of both anionic and cationic surfactants than in water. The gels which did not incorporate acrylic acid demonstrated little swelling in water, but showed increased swelling in both anionic and cationic surfactant solutions with increased hydrophobicity of the gel. Received: 1 February 1999 Accepted in revised form: 5 March 1999