Measurement Assurance of Phtalate Content: A Reference Material of Six Priority Phthalates in Methanol Solution

Abstract

The article provides information on the development of a new type of reference material (RM) of six priority phthalates (dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, benzyl butyl phthalate, di-2-ethyl hexyl phthalate, and di-n-octyl phthalate) in methanol solution, provided with metrological traceability to the GET 208–2019 (GET 208) national primary standard. The procedure for RM preparation and certification, including the homogeneity and stability assessment, is demonstrated. Pure organic substances (phthalates) characterised by the GET 208 primary standard were used as the starting material for the RM preparation using gravimetric and volumetric-gravimetric methods. The RM stability was assessed by an isochronous study. The mass fraction and mass concentration of individual phthalates in solution are the certified characteristics of the RM. The contributions from the purity of RM starting materials, preparation procedures, its heterogeneity and long-term instability were taken into account when calculating the uncertainty budget for the RM certified characteristics. The relative expanded uncertainty of certified values does not exceed 2%. As a result, the GSO (CRM) 11,366–2019 (6Ftlt-VNIIM) certified reference material of orthophthalic acid esters (phthalates) in methanol solution was developed and approved. The practical significance of using the GSO (CRM) 11,366–2019 consists in ensuring the metrological traceability of RMs to the corresponding SI units reproduced via the GET 208 national primary standard. The developed CRM can be used for different measuring tasks and metrological works.