Metrological support of phthalate content measurements: reference material for the composition of a solution of six priority phthalates in methanol

The article provides information on the development of a new reference material (RM) for the composition of a solution of six priority phthalates (dimethyl phthalate, diethyl phthalate, di(n-butyl) phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, di(n-octyl) phthalate) in methanol provided with metrological traceability to GET 208-2019 (GET 208). The procedure for the preparation and certification of RMs is shown, including the estimation of homogeneity and stability. Pure organic substances (phthalates) characterized on GET 208 were used as the starting material for the RM. The RM material was prepared by weight and volume-weight methods. The stability study of the RM was carried out by the isochronous procedure. The RM certified values are the mass fraction and mass concentration of individual phthalates in the solution. When calculating the uncertainty budget for RM certified values, contributions from the purity of the starting materials, RM preparation procedures, heterogeneity, and long-term instability were taken into account. The relative expanded uncertainty of the certified values does not exceed 2 %. As a result, a certified reference material (CRM) was developed and approvedfor the composition of a solution of ortho-phthalic acid esters (phthalates) in methanol GSO 11366-2019. The practical significance of the application of GSO 11366-2019 is to ensure the metrological traceability of RM to the corresponding SI units reproduced on GET 208. The developed CRM can be applied in resolving any measuring tasks and performing a full range of metrological works.