The Use of Gc-ms 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 Istituto Nazionale di Ricerca Metrologica (INRIM) to set density standards. The procedure involved accurate density determinations of some liquid samples, to be used as references, on which in addition analysis by means of gas-chromatography coupled with mass spectrometry (GC-MS) was performed to support homogeneity and short-term stability. In this exercise GC-MS analyses on two chlorinated liquids (namely tetrachloroethylene and trichloroethylene) were carried out before and after density measurements. The results obtained with the two different techniques were encouraging. Samples that had undergone to variations in density value showed also different gas-chromatographic profiles. In the same time, samples that had not undergone to density variations kept similar gas-chromatographic profiles. The results support the approach of combining independent methods in order to set physico-chemical properties of reference materials (RM), univocally.