PA.FPNS: its synthesis and use in spectrophotometric determination of magnesium

A new polymeric chromogenic reagent PA.FPNS has been synthesized by condensing polyallylamine (PA) with 3-(4-formylphenylazo)-4,5-dihydroxynaphthalene-2,7-disulfonic acid (FPNS) and its properties studied. In alkaline media, PA.FPNS reacts with magnesium to form a water-soluble blue complex, whose absorption maximum is at 604 nm. The molar absorptivity (varepsilon) of the complex is 5.2 x 10(4)l mol(-1) cm(-1), which is four times that of the FPNS-Mg complex, and Beer's law is obeyed over the range 0-0.35 mug ml(-1) magnesium. Compared to the corresponding low-molecular-weight FPNS and other chromogenic reagents, PA.FPNS offers considerably improved sensitivity and selectivity for magnesium, which may be attributed to incorporating FPNS into a water-soluble polymer and the effect of the polymeric chain on the reaction microenvironment. Also, a simple and sensitive spectrophotometric method for the determination of magnesium has been developed and applied to water and human fluid samples with satisfactory results.     

Crystalline titanium dichloride—an active catalyst in ethylene polymerization. II. Polymer structure,polymerization variables,and scope

Polymerization of ethylene with ball-milled titanium dichloride leads to a completely linear polymer with terminal unsaturation corresponding to approximately one carbon–carbon double bond per molecule. Polymerization rate is first-order in both monomer and catalyst concentration at 140°C. Due to a thermal deactivation of the catalyst, the polymerization rate falls sharply with temperature above 180°C. Propylene and butene-1 will copolymerization with ethylene in this system, propylene more efficiently than butene-1. Evidence for copolymerization of trans-2-butene, but not of the cis-isomer or of isobutene, in trace concentrations is presented. Propylene is homopolymerized to a product low in isotactic content. The significance of the structural and (limited) kinetic data in terms of the mechanism of polymerization are discussed.     

Instrumental neutron activation analysis of large samples: A pilot experiment

A large sample INAA (LS-INAA) was conducted based on available experimental conditions. Four different materials, e.g., a quartz-sand and three wastes from an incineration plant were analyzed on sample size of 1 kg. The neutron flux spatial distribution was determined by irradiation of flux monitors in the sample. The gamma-ray apparent counting efficiency was evaluated based on the effective-solid angle concept, using linear attenuation coefficients calculated from an iteration process. The k ₀- and the modified monostandard methods were modified for the LS-INAA. To check the LS-INAA performance, a conventional small sample INAA was carried out for the quartz sand and a waste. All detected elements in the LS-INAA are presented and the discussion is conducted to explore the sources of errors in the LS-INAA. As a pilot experiment, the information from this work will be used in constructing irradiation and counting devices for the new FRM-II neutron source in Garching, Germany.     

过氧化氢与N—甲基苯胺盐酸盐引发体系的研究

在水介质中,研究了新型的过氧化氢/N-甲基苯胺盐酸盐引发体系对 AM 与 PVA 的接枝共聚。产物经紫外光谱、红外光谱和 ~1H-核磁共振进行表征,并提出了引发机理。     

Direct injection of plasma to determine pseudoephedrine by high performance liquid chromatography with column switching

An HPLC method has been developed for the determination of pseudoephedrine in plasma using column switching. Preparation of the sample was simple in that only 1000 microL of water was added to 200 microL of plasma before injection. A 900 microL aliquot was injected onto the precolumn. Double distilled water was used to elute and remove proteins and polar components in the sample. The components retained on the precolumn were flushed forward onto the analytical column by the mobile phase (acetonitrile-0.2 mol/L ammonium sulphate, 10:90 v/v) with automated column switching. The limit of determination of pseudoephedrine in plasma was 12 ng/mL. The relative standard deviations of intra- and inter-assay for the determination of pseudoephedrine in plasma were 1.2-9.8% over the concentration range 1020-21.8 ng/mL. The mean recovery by on-line solid phase extraction was 94.76% (RSD = 1.1%).     

Differential determination of arsenic (III) and total arsenic with L-cysteine as prereductant using a flow injection non-dispersive atomic absorption device

Speciation of arsenic in environmental samples gains increasingly importance, as the toxic effects of arsenic are related to its oxidation state. A method was developed for the determination of trace amounts of arsenic (III) and total arsenic by flow injection hydride generation coupled with an in-house made non-dispersive AAS device. The total arsenic is determined after prereduction of arsenic (V) to arsenic (III) with L-cysteine in a low concentration of hydrochloric, acetic or nitric acid. The conditions for the prereduction, hydride generation and atomization were systematically investigated. A quartz tube temperature of 800 degrees C was found to be optimum in view of peak shape and baseline stability. Pb(II), Ni(II), Fe(III), Cu(II), Ag(I), Al(III), Ga(II), Se(IV), Bi(III) were checked for interfering with the 2 microg/L As(V) signal. A serious signal depression was only observed for Se(IV) and Bi(III) at a 150-fold excess. With the above system, arsenic was determined at a sampling frequency of about 1/min with a detection limit (3sigma) of 0.01 microg/L using a 0.5 mL sample. The reagent blank was 0.001+/-0.0003 absorbance units and the standard deviation of 10 measurements of the 2 microg/l As signal was found to be 1.2%. Results obtained for standard reference materials and water samples are in good agreement with the certified values and those obtained by ICP-MS     

An immune algorithm for resolution of multicomponent overlapping chromatograms

A novel immune algorithm for resolution and quantitative determination of the components in overlapping chromatograms was proposed by imitating biological immune systems. The algorithm takes an overlapping chromatogram as its input and subtracts the chromatograms of standard samples from the input by iteration of a network. When the residual does not change, the network will converge and chromatographic information of the components in overlapping chromatogram will be obtained. Both simulated and experimental data sets were investigated by the method. Results showed that both resolved results and recoveries of quantitative determination are satisfactory. Comparing with conventional least-square method, the immune algorithm is fast in calculation.     

Effect of particle size in preparative reversed-phase high-performance liquid chromatography on the isolation of epigallocatechin gallate from Korean green tea

To isolate epigallocatechin gallate (EGCG) of catechin compounds from Korean green tea (Bosung, Chonnam), a C18 reversed-phase preparative column (250x22 mm) packed with packings of three different sizes (15, 40-63, and 150 microm) was used. The sample extracted with water was partitioned with chloroform and ethyl acetate to remove the impurities including caffeine. The mobile phases in this experiment were composed of 0.1% acetic acid in water, acetonitrile, methanol and ethyl acetate. The injection volume was fixed at 400 microl and the flow rate was increased as the particle size becomes larger. The isolation of EGCG with particle size was compared at a preparative scale and the feasibility of separation of EGCG at larger particle sizes was confirmed. The optimum mobile phase composition for separating EGCG was experimentally obtained at the particle sizes of 15 and 40-63 microm in the isocratic mode, but EGCG was not purely separated at the particle size of 150 microm.     

DOPING LEVEL INCREASE OF POLY(3-METHYLTHIOPHENE)FILM DURING ELECTROCHEMICAL POLYMERIZATION PROCESS

The Raman spectra of poly(3-methylthiophene) (PMeT) films with different thicknesses, which have beenelectrochemically deposited on a flat stainless steel electrode surface by direct oxidation of 3-methylthiophene in borontrifluoride diethyl etherate (BFEE) at a constant applied potential of 1.38 V (versus SCE), have been investigated byexcitation with a 633-nm laser beam. The spectroscopic results demonstrated that the doping level of PMeT film wasincreasing during film growth. This finding was also confirmed by electrochemical examination. Moreover, the Raman bandsassigned to radical cations and dications in doped PMeT films were found approximately at 1420 and 1400 cm~(-1),respectively. Radical cations and dications coexist on the backbone of PMeT as conductive species and their concentrationsincrease with the increase of doping level. Successive cyclic voltammetry was proved to be an effective approach toimproving the doping level of as-grown thin compact PMeT film.     

Converged quantum calculations of HO2 bound states and resonances for J=6 and 10

Bound and resonance states of HO(2) are calculated quantum mechanically using both the Lanczos homogeneous filter diagonalization method and the real Chebyshev filter diagonalization method for nonzero total angular momentum J=6 and 10, using a parallel computing strategy. For bound states, agreement between the two methods is quite satisfactory; for resonances, while the energies are in good agreement, the widths are in general agreement. The quantum nonzero-J specific unimolecular dissociation rates for HO(2) are also calculated.