LIQUID-CHROMATOGRAPHY AMPEROMETRIC DETECTION OF CATECHOL, RESORCINOL, AND HYDROQUINONE WITH A COPPER-BASED CHEMICALLY MODIFIED ELECTRODE

A copper-based chemically modified electrode (CME) has been constructed and characterized for flow-through amperometric detection of catechol, resorcinol, and hydroquinone. Novel potential dependence of the detector response was first obtained for these analytes at the Cu CME, where negative peaks together with positive ones were observed in one definite chromatogram using amperometric detection. Its advantages in chromatographic applications were demonstrated. From these observations it is proposed that the detector response was governed by formation of copper complexes with the solutes. A dynamic linear range over two orders of magnitude was obtained, when operating the detector at +0.10 V vs. SCE, from which ng detection limits were achieved.

Controllable synthesis of VSB-5 micirospheres and microrods: Growth mechanism and selective hydrogenation catalysis

Nanoporous VSB-5 nickel phosphate molecular sieves with relatively well controllable sizes and morphology of microspheres assembled from nanorods were synthesized at 140 degrees C over a short time in the presence of hexamethylenetetramine (HMT) by a facile hydrothermal method. The pH value, reaction time, and ratio of HMT to NaHPO2-H2O crucially influence the morphology and quality of the final products.

Strings of interconnected hollow carbon nanoparticles with porous shells prepared using simple solid-phase synthesis

Strings of interconnected hollow carbon nanoparticles with porous shells were prepared by simple heat-treatments of a mixture of resorcinol-formaldehyde gel and transition-metal salts. The sample was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and nitrogen adsorption. Results show that the sample consisted of relatively uniform hollow particles with sizes ranging from 70 to 80 nm forming a strings-of-pearls-like nanostructure. The material with porous shells possessed well-developed graphitic structure with an interlayer (d(002)) spacing of 0.3369 nm and the stack height of the graphite crystallites of 9 nm.

An one-pot epitaxial growth method to synthesize cactus-like ZnO

In this work, we have developed a one-pot, morphology controlled epitaxial growth method to synthesize novel cactus-like ZnO in solution. Utilizing zinc acetate and hexamethylenetetramine as the precursors, ZnO nanorods synthesized in the first step remained in the solution, without any separation, served directly as the matrix for the epitaxial growth in the second step. Control experiments revealed that a proper mass of precursors added in the second step was crucial to form cactus-like ZnO. The as-synthesized ZnO was single crystalline and possessed three photoluminescence emissions centered at 390, 425 and 490 run. Finally, a possible mechanism for the epitaxial growth ZnO was proposed and discussed.

Syntheses and properties of thermotropic copolyesters of p-hydroxybenzoic acid

Two series of thermotropic copolyesters of p-hydroxybenzoic acid (HBA) were synthesized by direct thermal polycondensation. One comprised aromatic copolyesters from HBA, terephthalic acid, bis(4-hydroxyphenyl) ketone (BHP) and resorcinol. The other comprised semi-aromatic copolyesters from HBA, terephthalic acid, BHP and alpha,-diols with carbon atom number of 4, 6, 8, 10. The properties of the two series were characterized by polarized light microscopy, differential scanning calorimetry and wide angle X-ray diffraction. Most of the resulting copolyesters could form a nematic phase over a wide temperature range above their melting points. The effects of Variation in composition and monomer structure on the properties of copolyesters were discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.

Synthesis and properties of thermotropic liquid crystalline copolyesters containing bis(4-hydroxyphenyl)methanone(V)

A new series of fully aromatic thermotropic liquid crystalline copolyesters were synthesized by thermal polycondensation of p-hydroxybenzoic acid (PHB), terephthalic acid (TPA), resorcinol (RES) and bis (4-hydroxyphenyl) methanone (BHP). The DSC traces of copolyesters exhibited two or three endotherms, the low temperature endotherm(Tm) of which indicated the transition from solid state to anisotropic phase. Observation under polarizing microscope and WAXD measurements suggested that the LC-phase formed immediately above Tm had a nematic character.

Fluorescence spectroscopy studies on the action of rare earths with bovine serum albumin in multimolecular system

In this paper. the interaction of tripositive terbium ions (Tb3+) with bovine serum albumin (BSA) has been investigated in the presence of some alkaline earth metals and citric acid (Cit) by using fluorescence spectroscopy. The results show that Tb-31. BSA and Cit can form ternary complex BSA . Tb-2. Cit(4) in mu =0.1 mol/l NaCl. pH6.3 hexamethylenetetramine buffer. Other tare earths are able to compete for the same binding site in BSA with Tb3+-. The sequence of con,petition is Eu3+>Pr3+>Yb3+>Gd3+>La3+>Ca2+ and Mg2+ cannot replace Tb bound to BSA.

Electrocatalytic Oxidation of Dihydric Phenol on Polypyrrole Film Modified Electrodes

The electrochemical behavior of catechol, hydroquinone and resorcinol on GC and PPy/GC electrode surface were studied by CV and RDE method. The results indicated that these three substance could be oxidized electrocatalytically on PPy film electrode. The possibility of fabrication of amperometric electrochemical sensor for catechol was also studied.