TY - JOUR A1 - Westwood, S. A1 - Josephs, R. A1 - Choteau, T. A1 - Daireaux, A. A1 - Wielgosz, R. A1 - Davies, S. A1 - Moad, M. A1 - Chan, B. A1 - Munoz, A. A1 - Conneely, P. A1 - Ricci, M. A1 - Do Rego, E.C.P. A1 - Garrido, B.C. A1 - Violante, F.G.M. A1 - Windust, A. A1 - Dai, X. A1 - Huang, T. A1 - Zhang, W. A1 - Su, F. A1 - Quan, C. A1 - Wang, H. A1 - Lo, M. A1 - Wong, W. A1 - Gantois, F. A1 - Lalerle, B. A1 - Dorgerloh, Ute A1 - Koch, Matthias A1 - Klyk-Seitz, Urszula-Anna A1 - Pfeifer, Dietmar A1 - Philipp, Rosemarie A1 - Piechotta, Christian A1 - Recknagel, Sebastian A1 - Rothe, Robert A1 - Yamazaki, T. A1 - Zakaria, O. B. A1 - Castro, E. A1 - Balderas, M. A1 - González, N. A1 - Salazar, C. A1 - Regalado, L. A1 - Valle, E. A1 - Rodríguez, L. A1 - Laguna, L.Á.. A1 - Ramírez, P. A1 - Avila, M. A1 - Ibarra, J. A1 - Valle, L. A1 - Arce, M. A1 - Mitani, Y. A1 - Konopelko, L. A1 - Krylov, A. A1 - Lopushanskaya, E. A1 - Lin, T.T. A1 - Liu, Q. A1 - Kooi, L.T. A1 - Fernandes-Whaley, M. A1 - Prevoo-Franzsen, D. A1 - Nhlapo, N. A1 - Visser, R. A1 - Kim, B. A1 - Lee, H. A1 - Kankaew, P. A1 - Pookrod, P. A1 - Sudsiri, N. A1 - Shearman, K. A1 - Gören, A.C. A1 - Bilsel, G. A1 - Yilmaz, H. A1 - Bilsel, M. A1 - Cergel, M. A1 - Coskun, F.G. A1 - Uysal, E. A1 - Gündüz, S. A1 - Ün, I. A1 - Warren, J. A1 - Bearden, D.W. A1 - Bedner, M. A1 - Duewer, D.L. A1 - Lang, B.E. A1 - Lippa, K.A. A1 - Schantz, M.M. A1 - Sieber, J.R. T1 - Final report on key comparison CCQM-K55.c (L-(+)-Valine): Characterization of organic substances for chemical purity JF - Metrologia N2 - KEY COMPARISON Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM K55.c, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2012. Twenty National Measurement Institutes or Designated Institutes and the BIPM participated. Participants were required to assign the mass fraction of valine present as the main component in the comparison sample for CCQM-K55.c. The comparison samples were prepared from analytical grade L-valine purchased from a commercial supplier and used as provided without further treatment or purification. Valine was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of organic compounds of low structural complexity [molecular weight range 100–300] and high polarity (pKOW > –2). The KCRV for the valine content of the material was 992.0 mg/g with a combined standard uncertainty of 0.3 mg/g. The key comparison reference value (KCRV) was assigned by combination of KCRVs assigned from participant results for each orthogonal impurity class. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 1 mg/g to 6 mg/g when using mass balance based approaches alone, 2 mg/g to 7 mg/g using quantitative 1H NMR (qNMR) based approaches and from 1 mg/g to 2.5 mg/g when a result obtained by a mass balance method was combined with a separate qNMR result. The material provided several analytical challenges. In addition to the need to identify and quantify various related amino acid impurities including leucine, isoleucine, alanine and a-amino butyrate, care was required to select appropriate conditions for performing Karl Fischer titration assay for water content to avoid bias due to in situ formation of water by self-condensation under the assay conditions. It also proved to be a challenging compound for purity assignment by qNMR techniques. There was overall excellent agreement between participants in the identification and the quantification of the total and individual related structure impurities, water content, residual solvent and total non-volatile content of the sample. Appropriate technical justifications were developed to rationalise observed discrepancies in the limited cases where methodology differences led to inconsistent results. The comparison demonstrated that to perform a qNMR purity assignment the selection of appropriate parameters and an understanding of their potential influence on the assigned value is critical for reliable implementation of the method, particularly when one or more of the peaks to be quantified consist of complex multiplet signals. PY - 2014 DO - https://doi.org/10.1088/0026-1394/51/1A/08010 SN - 0026-1394 SN - 1681-7575 VL - 51 SP - 08010, 1 EP - 44 PB - Inst. of Physics Publ. CY - Bristol AN - OPUS4-31072 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grabmayer, K. A1 - Wallner, G.M. A1 - Beißmann, S. A1 - Braun, Ulrike A1 - Steffen, R. A1 - Nitsche, D. A1 - Röder, B. A1 - Buchberger, W. A1 - Lang, R.W. T1 - Accelerated aging of polyethylene materials at high oxygen pressure characterized by photoluminescence spectroscopy and established aging characterization methods JF - Polymer degradation and stability N2 - Two commercial polyethylene grades were exposed to water at elevated temperatures and enhanced oxygen pressure. To characterize their aging behavior laser-induced photoluminescence spectroscopy was applied. Additionally, aging characterization was performed by established methods such as tensile testing, infrared (IR) spectroscopy, high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and UV–VIS spectroscopy. During the initial stages of aging, the overall concentration of phenolic antioxidants as well as oxidation onset temperatures decreased exponentially. Simultaneously, significant discoloration due to the formation of conjugated degradation products from phenolic antioxidants (e.g., quinone methides) was detected. After the consumption of antioxidants, photoluminescence started to grow continuously presumably due to the formation of photoluminescent unsaturated carbonyls. In the final stages of aging, embrittlement of the materials as characterized by the degradation of mechanical properties (i.e., loss in ductility) coincided with rising carbonyl index values as well as an increase in crystallinity due to chemicrystallization. Between integrated photoluminescence intensity and carbonyl index, a linear correlation was established. In the induction period, the photoluminescence method exhibited a significantly higher sensitivity to reflect aging induced material changes. KW - Polyethylene KW - PE-RT KW - High oxygen pressure KW - Photoluminescence spectroscopy KW - Aging PY - 2014 DO - https://doi.org/10.1016/j.polymdegradstab.2014.06.021 SN - 0141-3910 SN - 1873-2321 VL - 109 SP - 40 EP - 49 PB - Applied Science Publ. CY - London AN - OPUS4-31349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -