Shigetomo Matsuyama

Precise measurement of the self-diffusion coefficient for poly(ethylene glycol) in aqueous solution using uniform oligomers

Uniform poly(ethylene glycol) (PEG) oligomers, with a degree of polymerization n=1-40, were separated by preparative supercritical fluid chromatography from commercial monodispersed samples. Diffusion coefficients, D, for separated uniform PEG oligomers were measured in dilute solutions of deuterium oxide (D(2)O) at 30 degrees C, using pulsed-field gradient nuclear magnetic resonance. The measured D for each molecular weight was extrapolated to infinite dilution. Diffusion coefficients obtained at infinite dilution follow the scaling behavior of Zimm-type diffusion, even in the lower molecular weight range. Molecular-dynamics simulations for PEG in H(2)O also showed this scaling behavior, and reproduced close hydrodynamic interactions between PEG and water. These findings suggest that diffusion of PEG in water is dominated by hydrodynamic interaction over a wide molecular weight range, including at low molecular weights around 1000.

Calibration of an evaporative light-scattering detector as a mass detector for supercritical fluid chromatography by using uniform Poly(ethylene glycol) oligomers.

The quantitativeness of an evaporative light-scattering detector (ELSD) for supercritical fluid chromatography (SFC) was evaluated by using an equimass mixture of uniform poly(ethylene glycol) (PEG) oligomers. Uniform oligomers, in which all molecules have an identical molecular mass, are useful for the accurate calibration of detectors. We calibrated the SFC-ELSD system for various concentrations and molecular masses by using an equimass mixture of PEG oligomers. ELSD not only showed a good linear response to the injected concentration over a wide concentration range, from 10(-4) to 10(-1)g/mL, but also showed a strong dependence on the molecular mass of the solute. By using chromatograms of the equimass mixture of uniform oligomers to calibrate SFC-ELSD, it was possible to determine exact values of not only the average mass but also the molecular-mass distribution for a PEG 1540 sample. The average molecular mass was shifted to a higher value by several percentage points after calibration of the ELSD.

Evaluation of the state-of-the-art measurement capabilities for selected PBDEs and decaBB in plastic by the international intercomparison CCQM-P114.

AbstractAn international intercomparison involving eight national metrology institutes (NMIs) was conducted to establish their current measurement capabilities for determining five selected congeners from the brominated flame retardant classes polybrominated diphenyl ethers and polybrominated biphenyls. A candidate reference material consisting of polypropylene fortified with technical mixtures of penta-, octa- and decabromo diphenyl ether and decabromo biphenyl, which was thoroughly assessed for material homogeneity and stability, was used as study material. The analytical procedures applied by the participants differed with regard to sample pre-treatment, extraction, clean-up, employed calibrants and type of calibration procedure as well as regarding analytical methods used for separation, identification and quantification of the flame retardant congeners (gas chromatography coupled to an electron capture detector (GC-ECD), gas chromatography-mass spectrometry in the electron ionisation mode (GC-EI-MS), gas chromatography-mass spectrometry in the electron capture negative ionisation mode (GC-ECNI-MS), and liquid chromatography-inductive coupled plasma-mass spectrometry (LC-ICP-MS)). The laboratory means agreed well with relative standard deviations of the mean of means of 1.9%, 4.8%, 5.5% and 5.4% for brominated diphenyl ether (BDE) 47, 183 and 209 and for the brominated biphenyl (BB) congener 209, respectively. For BDE 206, a relative standard deviation of 28.5% was obtained. For all five congeners, within-laboratory relative standard deviations of six measurements obtained under intermediate precision conditions were between 1% and 10%, and reported expanded measurements uncertainties typically ranged from 4% to 10% (8% to 14% for BDE 206). Furthermore, the results are in good agreement with those obtained in the characterization exercise for determining certified values for the flame retardant congeners in the same material. The results demonstrate the state-of-the-art measurement capabilities of NMIs for quantifying representative BDE congeners and BB 209 in a polymer. The outcome of this intercomparison (pilot study) in conjunction with possible improvements for employing exclusively calibrants with thoroughly assessed purity suggests that a key comparison aiming at underpinning calibration and measurement capability (CMC) claims of NMIs can be conducted. FigureMass fraction of deca-brominated diphenyl ether (BDE 209) in the polypropylene study material analysed in the international intercomparison CCQM-P114

Certification and uncertainty evaluation of the certified reference materials of poly(ethylene glycol) for molecular mass fractions by using supercritical fluid chromatography

AbstractPoly(ethylene glycol) (PEG) is a useful water-soluble polymer that has attracted considerable interest in medical and biological science applications as well as in polymer physics. Through the use of a well-calibrated evaporative light-scattering detector coupled with high performance supercritical fluid chromatography, we are able to determine exactly not only the average mass but also all of the molecular mass fractions of PEG samples needed for certified reference materials issued by the National Metrology Institute of Japan. In addition, experimental uncertainty was determined in accordance with the Guide to the expression of uncertainty in measurement (GUM). This reference material can be used to calibrate measuring instruments, to control measurement precision, and to confirm the validity of measurement methods when determining molecular mass distributions and average molecular masses. Especially, it is suitable for calibration against both masses and intensities for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. FigureComparison between the molecular mass fractions of PEG 1000 before calibration (si) (○) and after calibration (wi) (⧫). The error bar shows the expanded uncertainty of k = 2 of each mass fraction

Effects of Densities of Brominated Flame Retardants on the Detection Response for HPLC Analysis with a Corona-charged Aerosol Detector

Dependence of the response of a corona-charged aerosol detector (corona CAD) on the concentration and densities of brominated flame retardants and some related substrates was studied. The calibration curves of the substrates did not show linearity and the substrate with a lower density exhibited the stronger response. Regardless of the solvents (chloroform or toluene), and the injected volume of the substrate solution, the signal intensity of the substrate observed by a corona CAD was substantially proportional to 2/3 power law of concentration and proportional to (-2/3) power law of the density of the substrates. These results suggest that the responses should be proportional to the surface area of the particles generated through the drying process in corona CAD. Contrary to the former reports that the detector response of a corona CAD was independent of chemical species, it was proved that the response varies with the density of a substrate.

How does an oxygen atom in the side chain affect the photophysical properties of alkoxy-substituted organopolysilane homopolymers and copolymers?

Abstract Alkoxy-substituted organopolysilane homopolymer (poly[SiMe(OR)] n ) and random copolymers (poly[SiMe(OR)] m [SiMeR′] n were synthesized and the solvatochromism and thermochromism for their absorption and fluorescence spectra were examined. The band maxima shifted to longer wavelengths with an increase in the ratio of the alkoxy side chains; however, the influence of the solvent was very small. The thermochromic shifts are dependent on the number of alkoxy side chains. Molecular dynamics calculation showed that the conformation of the polysilanes was determined by the Coulomb interaction between the alkoxy side chains, and the conformations of the polyalkoxysilanes are similar to those of polyalkylsilanes (poly[SiRR′] n ). Molecular orbital (MO) calculations manifested that the interaction between the orbitals of the oxygen atom in the side chain and those of the silicon atom in main chain (σ conjugation system) was larger in LUMO than in HOMO, and the decrease in LUMO energy shifted the absorption maxima to longer wavelength.

Development of the Certified Reference Material of Poly(ethylene glycol) Nonylphenyl Ether by Supercritical Fluid Chromatography

Poly(ethylene glycol) nonylphenyl ether (PEG NPE) is a nonionic surfactant used widely as a detergent or industrial product, but the toxicity of nonylphenol, which is decomposed from PEG NPE, should be controlled to meet regulatory requirements. Under these situations, we plan to investigate the certified reference material in order to be able to exactly determine not only the average molecular weight but also all of the mole fractions of PEG NPE samples through the use of a well-calibrated evaporative light scattering detector coupled with high-performance supercritical fluid chromatography. In addition, experimental uncertainty was determined in accordance with the ISOs Guide to the Expression of Uncertainty in Measurement.

Influence of Impurities on Determination of Decabrominateddiphenyl Ether in Plastic Materials by Gas Chromatography/Mass Spectrometry

The effects of impurities on determining the concentrations of polybrominated diphenyl ethers (PBDEs) in plastic materials by gas chromatography coupled with mass spectrometry (GC-MS) were studied. Decabrominateddiphenyl ether (DBDE) extracted from a certified reference polystyrene (NMIJ CRM 8110-a) was analyzed by GC-MS with the use of 4,4′-dibromoctafluorobiphenyl (DBOFB) and pyrene as an internal standard and a syringe spike, respectively. DBDE concentration in the CRM was determined to be over 1100 mg/kg, although the certified value was 886 mg/kg. Among the various impurities identified in the CRM, paraffins proved to cause this discrepancy, because they showed a broad bump peak and were partially co-eluted with DBDE and pyrene on the chromatogram.

Molecularly uniform poly(ethylene glycol) certified reference material

A certified reference material (CRM) for poly(ethylene glycol) with no distribution in the degree of polymerization was developed. The degree of polymerization of the CRM was accurately determined to be 23. Supercritical fluid chromatography (SFC) was used to separate the molecularly uniform polymer from a standard commercial sample with wide polydispersity in its degree of polymerization. Through the use of a specific fractionation system coupled with SFC, we are able to obtain samples of poly(ethylene glycol) oligomer with exact degrees of polymerization, as required for a CRM produced by the National Metrology Institute of Japan.