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dc.contributor.authorPEREZ ALCAIDE JUAN ANDRESen_GB
dc.contributor.authorVANERMEN Guidoen_GB
dc.contributor.authorNOTEN Ben_GB
dc.contributor.authorLINSINGER Thomasen_GB
dc.date.accessioned2016-02-11T01:13:51Z-
dc.date.available2016-02-09en_GB
dc.date.available2016-02-11T01:13:51Z-
dc.date.created2016-02-08en_GB
dc.date.issued2016en_GB
dc.date.submitted2015-10-08en_GB
dc.identifier.citationACCREDITATION AND QUALITY ASSURANCE vol. 21 no. 1 p. 57-63en_GB
dc.identifier.issn0949-1775en_GB
dc.identifier.urihttp://publications.jrc.ec.europa.eu/repository/handle/JRC97838-
dc.description.abstractDuring the post-certification stability monitoring of the certified reference material (CRM) BCR-551 (DNPHderivatives dissolved in acetonitrile), a decreased concentration of one of the analytes of this CRM, formaldehyde DNPH-derivative, was detected in reference samples (stored at -70 °C) while normal "on sale" samples (stored at -20 °C) remained stable. This behaviour is contrary to the expectation of better stability at lower temperatures. Apparently, the formaldehyde DNPH-derivative reacts with dinitrophenylhydrazine (DNPH) left-over from the synthesis phase, to produce two new substances. These substances have been elucidated as C13H12N8O8 (substance 1) and C20H16N12O12 (substance 2) which, based on their structure, are suggested to be produced consecutively: DNPH + formaldehyde DNPH-derivative -> substance 1 substance 1 + formaldehyde DNPH-derivative -> substance 2 Since acetonitrile freezes at -45 °C, reference samples are frozen at -70 °C while normal samples are still liquid at -20 °C. We believe that this leads to a cryo-concentration of the solutes above the eutectic point and thus to an increased reaction rate in the reference samples. This case demonstrates that care should be taken when extrapolating stability results towards conditions that never have been tested, especially if phase transitions are involved, even at temperature as low as -70 °C. Furthermore, a slower degradation rate at lower temperatures can be overcompensated by a higher concentration due to cryo-concentration above the eutectic temperature.en_GB
dc.description.sponsorshipJRC.D.2-Standards for Innovation and sustainable Developmenten_GB
dc.format.mediumPrinteden_GB
dc.languageENGen_GB
dc.publisherSPRINGERen_GB
dc.relation.ispartofseriesJRC97838en_GB
dc.titleInstability of the DNPH-formaldehyde derivative in the certified reference material BCR-551 stored at -70 °C but not at -20 °Cen_GB
dc.typeArticles in periodicals and booksen_GB
dc.identifier.doi10.1007/s00769-015-1185-5en_GB
JRC Directorate:Health, Consumers and Reference Materials

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