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|Title:||Final report on key comparison CCQM-K55.c (L-(+)-Valine): Characterization of organic substances for chemical purity|
|Authors:||WESTWOOD Steven; JOSEPHS Ralf; CHOTEAU Tiphaine; DAIREAUX Adeline; WIELGOSZ Robert; DAVIES Stephen; MOAD Michael; CHAN Benjamin; MUNOZ-PINEIRO MARIA AMALIA; CONNEELY Patrick; RICCI Marina; PIRES DO REGO Cristina; GARRIDO Bruno; VIOLANTE Fernando; WINDUST Anthony; XINHUA Dai; HUANG Ting; ZHANG Wei; SU Fuhai; QUAN Can; WANG Haifeng; LO Man-Fung; WONG W.f.; GANTOIS Fanny; LALERLE Beatrice; DORGERLOH Ute; KOCH Matthias; KLYK-SEITZ Urszula Anna; PFEIFER Dietmar; PHILIPP Rosemarie; PIECHOTTA Christian; RECKNAGEL Sebastian; ROTHE Robert; YAMAZAKI Taichi; ZAKARIA Osman Bin; CASTRO E; BALDERAS M; GONZALEZ N; SALAZAR C; REGALADO L; VALLE E; RODRIGUEZ L; LAGUNA Angel; RAMIREZ P; AVILA M; IBARRA J; VALLE L; PEREZ M; ARCE M; MITANI Y; KONOPELKO Leonid; KRYLOV A; LOPUSHANSKAYA E; LIN Teo Tang; LIU Qinde; KOOI Lee Tong; FERNANDES-WHALEY Maria; PREVOO=FRANZSEN Desiree; NHLAPO Nontete; VISSER Ria; KIM Byungjoo; LEE Hwashim; KANKAEW Pornhatai; POOKROD Preeyaporn; SUDSIRI Nittaya; SHEARMAN Kittiya; GOREN Ahmet Ceyhan; BILSEL Gokhan; YILMAZ Hasibe; BILSEL Mine; CERGEL Muhiddin; COSKUN Fatma Gonca; UYSAL Emra; GUNDUZ Simay; UN Ilker; WARREN John; BEARDEN Daniel W.; BEDNER Mary; DUEWER David L.; LANG Brian; LIPPA K. A.; SCHANTZ Michele M.; SIEBER John R|
|Citation:||METROLOGIA vol. 51(1A):8010 p. 1-44|
|Publisher:||IOP PUBLISHING LTD|
|Type:||Articles in periodicals and books|
|Abstract:||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 α-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.|
|JRC Directorate:||Health, Consumers and Reference Materials|
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