Improvement of the quantitativeness of the thermal desorption-GC/MS method and development of polystyrene certified reference material for the quantification of decabromodiphenyl ether (BDE 209) by using isotope dilution mass spectrometry.

A polystyrene (PS) certified reference material (CRM) for the analysis of decabromodiphenyl ether (BDE 209) was issued. PS disk was prepared by injection molding of the mixture of versine PS and BDE 209. The certification of the PS CRM was conducted by two analytical methods with different sample preparation methods using isotope dilution mass spectrometry (IDMS). The certified value, wCRM, was 978 mg/kg, and this value coincided with the regulation value of BDE 209 in the Restriction of Hazardous Substances directive (1000 mg/kg). The uncertainties related to certification, uwmean, inhomogeneity, uhom, and long- and short-term instability, usts and ults, respectively, were evaluated based on the mass fraction of BDE 209. The uwmean, uhom, usts, and ults were 0.0265, 0.0046, 0.0061, and 0.0099 (relative), respectively, and the expanded uncertainty for this CRM was determined as 57 mg/kg (coverage factor is 2). Additionally, the quantitative capability of the thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was evaluated. In TD-GC/MS, the analytical values of the developed CRM obtained by the external and internal standard methods with matrix-free calibrants were out of the range of the wCRM (almost 10% larger or smaller), whereas those with matrix-matched calibrants agreed with the wCRM. In contrast to these results, the analytical values obtained by TD-GC/MS using IDMS were consistent with the wCRM no matter if matrix-free or matrix-matched calibrants were used. These results indicated that, for quantification of BDE 209 in PS, the trueness and precision of TD-GC/MS can be enhanced by applying IDMS without matrix-matched calibrants.

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.

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

Poly(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.

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.

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.

Evaluation of the quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using an equimolar mixture of uniform poly(ethylene glycol) oligomers.

Quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was elucidated using an equimolar mixture of uniform poly(ethylene glycol) (PEG) oligomers with no molecular weight distributions. Uniform PEG oligomers with degrees of polymerization n = 6-40 were separated from commercial PEG samples by preparative super-critical fluid chromatography. MALDI-TOF mass spectra of an equimolar mixture of the uniform PEG oligomers were recorded by adding a mixture of 2,5-dihydroxybenzoic acid as a matrix reagent and four chlorinated salts, i.e. LiCl, NaCl, KCl and RbCl. Remarkable non-quantitative effects were observed in the MALDI-TOF mass spectra in both the lower and higher molecular mass regions. At higher molecular masses greater than about 10(3), PEG oligomers with larger molecular mass yielded lower spectral intensities irrespective of the species of adduct cations and higher laser powers induced larger decreases in mass spectral intensities with the increase in their molecular masses. On the other hand, in the lower molecular mass region, less than about 10(3), the observed non-quantitative effect greatly depends on the species of adduct cations, indicating that the stability of the PEG-cation complex affects the MALDI-TOF mass spectral intensities of uniform PEG oligomers.