In the context of the rapid development of the Russian pharmaceutical industry, there is an urgent need to improve the State Primary Standard for the units of mass (molar) fraction and mass (molar) concentration of organic components in liquid and solid substances and materials based on liquid and gas chromatography-mass spectrometry with isotope dilution and gravimetry (GET 208).

As a result of the improvement of GET 208 carried out in 2023, a new installation based on the highperformance liquid chromatography/high-resolution mass spectrometry method was included in the standard. Thus, the functionality of the GPE was expanded in accordance with the current requirements of the domestic industry and for the purpose of Russia’s successful participation in international comparisons in the field of organic analysis now and in the medium term.

The article presents materials on the study of the capabilities of the new installation for solving various measurement problems in the field of organic analysis, describes specific analytical techniques and measurement methods, and provides experimental data and summarized results. Based on the completed studies, the metrological characteristics of GET 208 have been improved in terms of reproducing units of mass (molar) fraction of the main component in pure organic substances, mass fraction of organic components in solutions and materials.

Improvement of GET 208 made it possible to create a scientific, methodological and instrumental basis for reproducing measurement units for a wide range of organic compounds.

Determination and assignment of reasonable intervals between certifications of standards is an important task to ensure the uniformity of measurements. The standards are intended for further transfer of the unit to standards and measuring instruments lower down the verification scheme, which means that exceeding the permissible values by metrological characteristics during operation is unacceptable, since it may lead to unreliability of the further transfer of the unit along the traceability chain. This risk can be reduced by finding the optimal interval between certifications, during which the metrological characteristics of the standard will not exceed the permissible values.

The article proposes one of the options for determining the interval between certifications based on the analysis of the measurement model of the standard and modeling the time dependence of the error limits of the estimates of input quantities, including taking into account factors that are not directly involved in the measurement process but influence this process.

The article introduces the development of reference materials of benzoic and sorbic acids with a certified value of the mass fraction of the main substance. The development of reference materials was carried out in several stages: identification, characterization, study of homogeneity and stability of reference materials. Identification of candidate materials for reference materials was carried out by IR Fourier spectroscopy and determination of melting point by differential thermal analysis. The candidate materials for reference materials were characterized by the indirect method «one hundred minus the sum of impurities» with confirmation of the measurement results by the direct method – the acid-base titration method. It was established that the measurement results of the mass fraction of the main substance of benzoic and sorbic acids obtained by the acid-base titration method and the mass balance method are consistent with each other taking into account the values of expanded uncertainties. The work was carried out using primary and secondary standards. The accuracy of the measurement results of the mass fraction of the main substance was increased by searching for and selecting optimal measurement modes when determining each type of impurity. The homogeneity of materials was determined using the one-way analysis of variance method; stability was determined using the regression analysis method.

The developed reference materials of benzoic and sorbic acids were included in the Federal Information Fund for Ensuring the Uniformity of Measurements as GSO 12297–2023 and GSO 12298–2023. The certified value of the mass fraction of the main substance is in the range from 95.00 to 100.00 %, the limits of the permissible values of the absolute error at P = 0.95 are ± 0.5 %.

The use of GSO 12297–2023 and GSO 12298–2023 for certification and control of the accuracy of methods, establishment and control of the stability of calibration characteristics of measuring instruments, verification, calibration of measuring instruments can improve the quality of food products, food raw materials and pharmaceuticals.

In order to ensure metrological traceability of fat mass fraction measurements, the State Primary Reference Measurement Procedure (SPRMP) for the Determination of Mass Fraction of Fat in Food Products and Food Raw Materials was developed, certified and approved in 2018. The SPRMP applies to samples of milk powder, sour cream, cottage cheese, cheese, meat and meat products, dry egg products, milk mixtures, grain porridge, grain-milk mixtures, canned baby food and establishes requirements for the procedure for measuring the mass fraction of fat using the Randall extractiongravimetric method. In the process of applying the SPRMP, the need to expand the scope of its application was identified. The purpose of the research is to improve the SPRMP of the mass fraction of fat in food products and food raw materials. An analysis of regulatory documents defining requirements for new measurement objects, measurement ranges and accuracy indicators has been completed. The measurement parameters and their permissible variation limits for new objects have been established. As a result of improvement, the scope of application of the SPRMP includes drinking milk and cream, condensed milk and cream, fish fillet, fish meat, including minced meat, bakery products, f lour confectionery, pasta, cocoa powder, chocolate, flour from cereals, nuts, nut paste, including peanut. An assessment of the accuracy indicators of the SPRMP was carried out using certified reference materials, food products and food raw materials. The developed measurement procedure made it possible to ensure a margin of accuracy of the measurement results using the SPRMP in comparison with standardized measurement procedures from 2 to 25 times, depending on the object and the measurement range. As part of the interlaboratory comparison tests, the procedure for using the SPRMP to assess the correctness of measurement results obtained using standardized measurement procedures was tested. During the COOMET pilot comparisons, as well as the analysis of foreign reference materials, the equivalence of the SPRMP to similar measurement methods of foreign countries was demonstrated. The applicability of the SPRMP for determining the certified value of the mass fraction of fat during the characterization of reference materials was demonstrated.

Metrological support of gas analytical measurements is carried out by transferring units of molar fraction and mass concentration of components from the State Primary Standard of units of molar fraction, mass fraction and mass concentration of components in gas and gas condensate environs. Reference materials (RMs) for the composition of gas mixtures in cylinders under pressure are used as transmission means, as well as gas mixture generators, the output of which is a gas mixture with known metrological characteristics. The main problem of this method is to ensure long-term stability of the mixture. The use of dynamic methods implemented in gas mixture generators, when the prepared gas mixture is used directly from the generator output, allows to significantly minimize or completely avoid this problem.

In recent years, quite a lot of gas mixture generators manufactured by domestic and foreign manufacturers have appeared on the market. Therefore, a comparative analysis of various methods of dosing the initial components implemented in gas mixture generators and used for metrological support of gas analytical measurements seems relevant.

The practical significance of the study lies in the analysis of the metrological, technical and operational characteristics of generators implementing various methods of dosing components of gas mixtures, which can be used by manufacturers of these measuring instruments to develop optimal technical solutions in the development and creation of new types of generators and dynamic installations designed to reproduce and transmit units of component content in gas environs.

The presented review may be useful for teachers and students of specialized higher education institutions to enhance their knowledge in the field of metrological support for gas analytical measurements.

The problem of estimating the measurement uncertainty near the natural measurand limits is of significant interest to practicing metrologists and is far from being resolved. The article considers the Bayesian approach to constructing an asymmetric coverage interval and estimating measurement uncertainty in the case where the set of permissible values of the measured quantity is bounded. Of particular interest is the case when the measured value is located near the boundary of the set of its permissible values, since the constructed «traditional» symmetric interval corresponding to a coverage factor value of two (for a confidence level of 95 %) goes beyond the boundaries of this set and, as a consequence, do not provide the specified level of confidence probability.

When implementing the Bayesian approach, an important starting point is the choice of a priori density distribution. Four options for choosing a prior probability density are considered, including an asymmetric distribution from the family of two-sided power distributions (TSP). Recommendations are given for their selection and application depending on the proximity of the a priori estimate of the lower limit of the measured value, as well as the measured value, to the upper limit of the range of permissible values, relative to the measurement uncertainty value.

A specialized software has been developed to estimate the posterior density characteristics (expectation, mode and standard deviation) of measurand distributions and construct the shortest coverage interval, as well as to calculate the confidence level corresponding to the «traditional» coverage interval obtained using expanded uncertainty. The use of this software allows to obtain complete information about the measurement accuracy and to make an informed choice when presenting the measurement result.

The results obtained may be of interest to practicing metrologists in the development and certification of measurement techniques, processing of experimental data and presentation of measurement results when characterizing standard samples, as well as specialists involved in the application of methods of probability theory and mathematical statistics in solving practical problems.

The authors were prompted to discuss the practice of using the X-ray fluorescence for measuring coating thickness in the scientific community by the high demand for the method, which is constantly growing in the Russian Federation as the high-tech sector of mechanical engineering, instrument making and electronics develops in the country.

The review presented in the article can predetermine the prospects for improving the metrological support of the X-ray fluorescence spectrometry and, more broadly, in the field of non-destructive measurements of coating thickness in general. The authors collected and systematized bibliographic material on types of coatings, methods of their application, advantages and limitations of non-destructive measurements of coating thickness. Based on these data, questions are formulated that can provide direction for scientific research aimed at developing non-destructive methods for testing coating thickness.

The published material is addressed primarily to metrologists providing control in this area and manufacturers of instruments and means for monitoring the quality of coatings. The authors allow the development of the discussion taking into account the opinion and experience of using non-destructive testing of coating thickness in the conditions of the current production.