The use of GCMS to support stability assessment of density reference liquids

Density measurements are frequently associated to specific requirements in order to evaluate the quality of a process or to determine mass and/or volume of the material. Certified reference liquids can be used to assure metrological traceability of density measurements to the International System of Units - SI with uncertainty lower than 0.005 %. This paper presents the new approach of the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica - INRIM) to set density standards. The procedure has involved accurate density determinations of some liquid samples intended to be used as references with, in addition, analysis by means of gas-chromatography coupled with mass spectrometry (GC-MS) to support the short-time stability in addition to assess that any sample had not been polluted during the density investigation. In this exercise analyses on various liquid were carried out before and after density measurements. Changing in the composition of some tested samples has been observed as well as changing of the density values. The results show a good sensitivity in combining independent methods in order to set physico-chemical reference materials