Water content variation of p-n-heptylphenol reference material

Abstract

Water content variation of candidate p-n-heptylphenol (HP) reference material (ampoule form) for preparation of a primary standard solution based on the Japan Calibration Service System, a national standards dissemination system, under the Measurement Law of Japan, was examined by a Karl-Fischer water content meter. As prepared samples, liquid-phase HP and upper, middle, and lower layers of solid-phase HP were measured since characteristic phase transition occurs near room temperature (melting point: 28.98 °C). As a result of water content in liquid- and solid-phase HP, water content variation among three layers of solid-phase is found in within ampoules, though water content variation of liquid-phase is not found. Between-ampoule variation of water content is also found using total ampoules of liquid-phase HP used to eliminate within-ampoule variation. Moreover, water content variation is secondarily confirmed by the results of the amount-of-substance fraction of HP based on a differential scanning calorimeter. From these results in this study, it is concluded that within- and between-ampoule variations of water content may depend on phase transition and water loss during ampouling of candidate reference material, respectively.