Biological effect of rare earth (I) - Content and distribution of rare earth in normal human plasma

The content and distribution of rare earth(RE) in normal human plasma have been investigated by ultrafiltration, FPLC and ICP-MS methods, The results showed that there are trace RE in normal human plasma, and their contents are in accordance with their abundance, The RE can bond with immunoglobulin G(IgG), transferrin(Tf) and albumin(Alb) species, but mostly bond with Tf.

Donut-shaped spray chamber for inductively coupled plasma spectrometry

A donut-shaped spray chamber has been developed for the introduction of aerosol and/or volatile chemical species into the inductively coupled plasma. Compared with the Fassel-Scott spray chamber, it gives a higher efficiency of aerosol generation and transportation and superior stable inner pressure. As a result, it brings the benefits of higher intensity signal, lower background, higher measurement precision, and better detection limits. Using:his spray chamber, it is more convenient to introduce volatile chemical species into the sampling system, and more flexible for the choice of introducing aerosol and volatile chemical species separately or simultaneously into the plasma. It is also suitable for FIA technique. (C) 1998 Elsevier Science B.V. All rights reserved.

Chemical bond analysis of nonlinearity of urea crystal

A novel and quantitative study on structure-property relationships has been carried out in urea crystal, based on the dielectric theory of complex crystals and the modified Levine bond charge model, mainly from the chemical bond viewpoint. For the first time, it was treated like this, and the bond parameters and linear and nonlinear characteristics of constituent chemical bonds were presented quantitatively. The theoretical result agrees satisfactorily with the experimental datum and can reasonably explain the nonlinear origin of urea crystal, that is, the C-N bond in the conjugated system of bonds O double left arrow C<--N-H. At the same time, the novel method should be a useful tool toward the future development of the search for new nonlinear optical (NLO) materials in the organic crystal field.

Plasma modification of aromatic polyamide reverse osmosis composite membrane surface

The surface of aromatic polyamide reverse osmosis composite membrane was modified by oxygen and argon plasma. The water permeability of oxygen-plasma-modified membrane increases, and the chlorine resistance of argon-plasma-modified membrane increases. The spectra of the attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy and the contact angle of the water were analyzed to explain the improvement of the two performances of the composite membrane. The carboxyl groups were introduced when modified by oxygen plasma, and cross-linking occurred when modified by argon plasma. (C) 1997 John Wiley & Sons, Inc.

Effect of urea on synchronous fluorescence spectra and electrochemical behaviour of cytochrome c

The changes of the synchronous fluorescence spectra and the electrochemical behaviour of cytochrome c with the urea concentration are studied. It has been found that with the increase of urea concentration, there occur sequentially the deaggregation of cytochrome c molecules, the increase of exposure extent of the heme group to the solvent, the disruption of Fe-S bond of the heme group and the change in the electrochemical behaviour of cytochrome c. It is suggested that the reason why the electrochemical reaction of cytochrome c is irreversible is that cytochrome c molecules exist in the concentrated solution as oligomers which are electrochemically inactive.

Electrochemical identification of intermediate forms of urea denaturation of horse heart cytochrome c

The electrochemical identification of the urea denaturation of horse heart cytochrome c in bulk solution at the 4,4'-dithiodipyridine-modified gold electrode is reported. The results are similar to the three-step transitions of equilibrium studies (Myer et al., Biochemistry, 19 (1980) 199) of urea denaturation of cytochrome c in bulk solution. This method permits a clear resolution of which of the three steps of urea denaturation is electrochemically related. In addition, by analysing the effects of urea on the structural forms of cytochrome c and on the solution properties, as well as the cyclic voltammetric responses of the protein, the individual forms of the urea denaturation of cytochrome c can be understood. The results reflect the superposition of protein denaturation on the electrode surface and in solution.

SIMULTANEOUS DETERMINATION OF GUANINE, URIC-ACID, HYPOXANTHINE AND XANTHINE IN HUMAN PLASMA BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH AMPEROMETRIC DETECTION

A reversed-phase high-performance liquid chromatographic method with amperometric detection is described for the separation and quantification of uric acid, guanine, hypoxanthine and xanthine. The isocratic separation of a standard mixture of the compounds was achieved in 5 min on a Spherisorb 5 C-18 reversed-phase column, with a mobile phase of NaH2PO4 (300 mmol dm(-3) pH 3.0)-methanol-acetonitrile-tetrahydrofuran (97.8 + 0.5 + 1.5 + 0.2). Uric acid, guanine, hypoxanthine and xanthine were completely separated, with detection limits in the range 2-20 pmol per injection. The effect of pH and the composition of the mobile phase on the separation are described. The hydrodynamic voltammograms of these compounds were recorded at a glassy carbon electrode. The linear range of the calibration graph for each compound was: uric acid; 1-5000 mu mol dm(-3); guanine, 0.5-2000 mu mol dm(-3); hypoxanthine, 0.1-500 mu mol dm(-3) and xanthine, 0.5-5000 mu mol dm(-3). The within- and between-day precision was good. The uric acid and hypoxanthine content in human plasma was measured using the proposed method. Good recoveries of uric acid (97.9-103%), hypoxanthine (98.0-99.2%), guanine (96.0-98.3%) and xanthine (96.0-102%) were obtained from human plasma. The results of electrochemical detection were in good agreement with those of UV detection.

DETERMINATION OF CYSTEINE AND REDUCED GLUTATHIONE IN HUMAN PLASMA BY LIQUID-CHROMATOGRAPHY WITH PULSED AMPEROMETRIC ELECTROCHEMICAL DETECTION USING A PLATINUM-PARTICLES MODIFIED GLASSY-CARBON ELECTRODE

An assay procedure utilizing pulsed amperometric detection at a platinum-particles modified electrode has been developed for the determination of cysteine and glutathione in blood samples following preliminary separation by reversed-phase liquid chromatography. A chemically modified electrode (CME) constructed by unique electroreduction from a platinum-salt solution to produce dispersed Pt particles on a glassy carbon surface was demonstrated to catalyze the electo-oxidation of sulfhydryl-containing compounds: DL-cysteine (CYS), reduced glutathione (GSH). When used as the sensing electrode in flow-system pulsed-amperometric detection (PAD), electrode fouling could be avoided using a waveform in which the cathodic reactivation process occurred at a potential of - 1.0 V vs. Ag/AgCl to achieve a cathodic desorption of atomic sulfur. A superior detection limit for these free thiols was obtained at a Pt particle-based GC electrode compared with other methods; this novel dispersed Pt particles CME exhibited high electrocatalytic stability and activity when it was employed as an electrochemical detector in FIA and HPLC for the determination of those organo-sulfur compounds.

PLASMA-INDUCED GRAFTING OF STYRENE ONTO NASCENT POLYETHYLENE POWDER

In this paper, the graft copolymers of styrene to nascent linear polyethylene reactor powders were prepared through plasma graft polymerization. The grafting reaction was initiated by the alkyl radicals formed on the surface of nascent polyethylene with plasma treatment as indicated by electron spin resonance spectra. In graft copolymerization by alkyl radicals, the grafting yield increased with either the plasma power or the plasma treatment lime. Compared with ordinary polyethylene powders, nascent polyethylene reactor powders were found to be more easily plasma-grafted. This has been attributed to the greater sensitivity to irradiation in producing reactive centres under the same conditions. High density polyethylene showed almost the same grafting yield as linear low density polyethylene at 50 degrees C. The surface morphology of nascent polyethylene observed by scanning electron microscope before and after the grafting showed that the silk-like fibrils were not destroyed by plasma treatment.

A DIFFERENTIAL SCANNING CALORIMETRY STUDY OF PLASMA IRRADIATION GRAFTING OF NASCENT POLYETHYLENE REACTOR POWDER

The melting behavior of poly(methyl methacrylate)-grafted nascent polyethylene reactor powder by plasma irradiation was studied by differential scanning calorimetry (DSC). The grafting yield ranged hom 11 to 190%. Grafting was found to lower both melting point and heat of fusion during the first run of DSC determination. The heat of fusion was used to calculate the apparent grafting yield of the samples. There was little strain induced by plasma-irradiated grafting on the surface of the polyethylene crystals. A method to determine the covalent grafting yield in the graft copolymer systems was developed. (C) 1995 John Wiley & Sons, Inc.

ELECTROCHEMICAL MECHANISM FOR FULLERENE FORMATION IN PLASMA ARCS

During the synthesis of fullerenes by dc plasma arcs, it has been found that the anodic graphite rod consistently burns up, while the cathodic graphite rod grows slag at its end. Further investigations revealed that the anodic and cathodic graphite rods p

IMPROVEMENT OF OXYGEN NITROGEN PERMSELECTIVITY OF POLY[1-(TRIMETHYLSILYL)-1-PROPYNE] MEMBRANE BY PLASMA POLYMERIZATION

The oxygen permselectivity of a poly[1-(trimethylsilyl)-1-propyne) (PTMSP) membrane was drastically improved by plasma polymerization of fluorine-containing monomers. The effects of such plasma polymerization conditions as deposition time, plasma power an

RESOLUTION OF CLOSELY SPACED LINES WITH KALMAN FILTERING IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

Effects of some factors on the performance of our Kalman filter in discrimination of closely spaced overlapping signals were investigated. The resolution power of the filter for overlapping lines can be strengthened by reduction of the step size in scans. The minimum peak separation of two lines which the Kalman filter can effectively handle generally equals two to three times the step size in scans. Significant difference between the profiles of the analysis and interfering lines and multiple lines from matrix in the spectral window of the analysis line are very helpful for the Kalman filter to discern closely spaced analysis and interfering signals correctly, which allow the filter well to resolve the line pair with very small peak distance or even the entirely coincident lines.

ON THE SIGNIFICANCE OF WAVELENGTH POSITIONING ACCURACY IN MULTICOMPONENT ANALYSIS TECHNIQUES FOR THE CORRECTION OF LINE INTERFERENCES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

The present paper reports some definite evidence for the significance of wavelength positioning accuracy in multicomponent analysis techniques for the correction of line interferences in inductively coupled plasma atomic emission spectrometry (ICP-AES). Using scanning spectrometers commercially available today, a large relative error, DELTA(A) may occur in the estimated analyte concentration, owing to wavelength positioning errors, unless a procedure for data processing can eliminate the problem of optical instability. The emphasis is on the effect of the positioning error (deltalambda) in a model scan, which is evaluated theoretically and determined experimentally. A quantitative relation between DELTA(A) and deltalambda, the peak distance, and the effective widths of the analysis and interfering lines is established under the assumption of Gaussian line profiles. The agreement between calculated and experimental DELTA(A) is also illustrated. The DELTA(A) originating from deltalambda is independent of the net analyte/interferent signal ratio; this contrasts with the situation for the positioning error (dlambda) in a sample scan, where DELTA(A) decreases with an increase in the ratio. Compared with dlambda, the effect of deltalambda is generally less significant.