Research of the random and systematic components of measurement error of the triglycerides mass fraction in the certified reference material of milk fat to extend its shelf life

In the certified reference materials, the quantity of substances is known with uncertainty, which is enough to use them as a reference (base) when measuring the quantity of the same substances in the tested product sample. The stability of substance quantity in the reference materials is the key to reliable tests. The problem of extending the certificate validity period for reference materials arises because the necessary certified reference materials may not be available on the market at the moment. Moreover, the certified reference materials are quite expensive, and the renewal of their certificates is economically viable. A method for proving the stability of the amount of substance in the certified reference materials has been proposed. This method is based on the analysis of random and systematic components of the error during the laboratory's internal control measurements and interlaboratory comparisons. Using the developed method, the stability of the mass concentration of milk fat in the certified reference material BCR-519 has been proven.