Algorithm for Determining the Purity of Pure Organic Phthalates by the Indirect Mass Balance Method

Pure organic substances are the first and key link in the chain of metrological traceability in organic analysis. In most cases, purity determination of the organic substance is a non-trivial task, the solution of which requires preliminary theoretical study and understanding of the capabilities of instrumental methods for developing a pertinent analytical procedure.

Within the study, an algorithm for determining the purity of a separate group of organic compounds – ortho-phthalic acid esters (phthalates) was developed based on the mass balance model and the general algorithm for characterizing substances suitable for isolation or purification by distillation. An additional classification of probable impurities (into five types A – E) depending on their qualitative and quantitative characteristics is proposed, as well as suitable analytical methods for measuring impurities and confirming the identity of the main component are identified.

The proposed algorithm was implemented on the State Primary Standard GET 208 to determine the purity of six priority phthalates: dimethyl phthalate, diethyl phthalate, di-(n-butyl) phthalate, benzyl butyl phthalate, di-(2-ethylhexyl) phthalate, and di-(n-octyl) phthalate. Certified pure phthalates were used to create a certified reference material for the composition of a solution of orthophthalic acid esters (phthalates) in methanol (6Ftlt-VNIIM) GSO 11366–2019.

The study revealed that the adapted algorithm considers the specifics of work with the phthalates group and the features of the separation of probable impurities within the MB model, and is universal for all congeners of the group, but does not exclude the natural constraints of the mass balance method.

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