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We have developed a unique dynamic dilution system for generating high accuracy reference standards of reactive gases at concentrations which are unstable in high pressure cylinders. It uses state of the art ‘Molbloc’ flow elements and is capable of generating adjustable reference standards with an estimated relative expanded uncertainty lower than 1%. This is a significant development, improving the accuracy of primary reference gas mixtures used to provide and disseminate traceability for measurements of many key gaseous air pollutants.

The National Institute of Metrological Research (INRiM), in Italy, has among its duties the development, the maintenance and the dissemination of primary standards for establishing a correct traceability chain at national level. For this reason, INRiM has been developing research activities on reference materials, mainly in the chemical field, dealing both with the characterization and the certification of reference materials. The present paper focuses on the certified reference solutions for electrolytic conductivity, on the primary reference gas mixtures, and on INRiM contribution in the certification of various reference materials by determining trace element mass fraction by means of Instrumental Neutron Activation Analysis. The description of the main features of the produced reference materials, of the used procedures, and of the uncertainty evaluation are given.

Metrology in chemistry has its own features, which distinguish it from classical metrology: due to the lack of primary methods applicable in routine measurements, metrological traceability of measurement results can be achieved by using in a proper way suitable certified reference materials (CRMs), which can assure a direct relation to a reference. This article deals with the activity of the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.) on the analysis of various polychlorinated biphenyls congeners in organic solution by means of gas-chromatography coupled with mass spectrometry. The metrological traceability approach in the quantification step is pursued via calibration solutions prepared by gravimetrically diluting a CRM. The uncertainty for the calibration solutions was evaluated taking into account all the relevant contributions.

Metrologically traceable measurements are needed, in environmental monitoring, to provide meaningful information on the pollution level and the possibility to have suitable reference standards is crucial to this purpose to calibrate instruments. The Italian National Institute of Metrological Research (I.N.Ri.M.), as a primary metrological institute, realizes and maintains primary standards for the basic and derived units of the International System of Units (SI). In this framework and regarding gas analysis, in the last few years I.N.Ri.M. has started a research line on the preparation of primary reference mixtures (PRMs) by the gravimetric method that led to plan and build a facility for evacuating and filling cylinders and a device for high precision weighing. In the present work the developments in such field at I.N.Ri.M. are reported to underline the relevance, in the atmospheric pollutants monitoring, of performing accurate and reliable measurements and having reference standards fit for the calibration of the analytical instrumentation.