Generation of CO2 gas mixtures by dynamic dilution for the development of gaseous certified reference materials

The use of Certified Reference Materials (CRMs) is of utmost importance to achieve the comparability and traceability of data, which are essential features of measurement results in environmental and climate fields. The present paper focuses on the generation of gas mixtures at known composition of carbon dioxide at atmospheric amount-of-substance fraction in synthetic air by means of a dynamic dilution system, designed and implemented at the Istituto Nazionale di Ricerca Metrologica (INRiM). The validation of the dynamic system in terms of amount-of-substance fraction is presented. The system was also used to verify the carbon dioxide amount-ofsubstance fraction of a suite of gas mixtures gravimetrically prepared at INRiM in the framework of the EMPIR Joint Research Project 19ENV05 – STELLAR. Dynamic dilution proved to be an effective tool for the preparation and certification of CRMs for gaseous pollutants (i.e. carbon dioxide, nitrogen oxides) relevant for monitoring environmental pollution and climate changes

A portable setup for the voltammetric determination of total mercury in fish with solid and nanostructured gold electrodes

A simple procedure for field fish sample pretreatment was developed. This treatment in combination with square wave anodic stripping voltammetry (SW-ASV) with solid gold electrodes (SGE) and gold nanoparticle-modified glassy carbon electrodes (AuNPs-GCE) was applied for the determination of total mercury content. A certified reference material (CRM, Tuna Fish BCR 463), ten freeze-dried samples of canned tuna and two fresh fish samples were analysed both with a bench-top voltammetric analyser after microwave digestion and with a portable potentiostat after mild eating using a small commercial food warmer. The results obtained by the two SW-ASV approaches and by a Direct Mercury Analyser (DMA), the official method for mercury determination, were in very good agreement. In particular, (i) the results obtained with in field procedure are consistent with those obtained with the conventional microwave digestion; (ii) the presence of gold nanoparticles on the active electrode surface permits an improvement of the analytical performance in comparison to the SGE: the Limit of Quantification (LOQ) for mercury in fish-matrix was 0.1 μg L−1 (Hg cell concentration), corresponding to 0.06 mg kg−1 wet fish, which is a performance comparable to that of DMA. The pretreatment proposed in this study is very easy and applicable to fresh fish; in combination with a portable potentiostat, it proved to be an interesting procedure for on-site mercury determination

Realisation of gas reference materials of CO2 in air at known isotopic composition

The accurate and reliable determination of carbon dioxide (CO2) levels in atmosphere, together with its isotopic composition, is fundamental to monitor the trends of this gas in atmosphere and to support the prediction of its future increase on a global scale. The determination of the isotopic composition of CO2 can support the assessment of the uptake of CO2 in the environmental compartments, and can help to distinguish natural from anthropogenic carbon in the atmosphere. In this regard, INRIM started an activity for the development of new reference gas mixtures of CO2 at ambient amount fraction in high pressure cylinders with different isotopic compositions, to cover the range -48 ‰ to -8 ‰ vs VPDB for δ13C and -27 ‰ to +2 ‰ vs VPDB for δ18O, with uncertainty targets of 0.1 ‰ for δ13C-CO2 and 0.5 ‰ for δ18O-CO2. The activity was carried out in the framework of the EMPIR project 16ENV06 “Metrology for stable isotope reference standards - SIRS”, and it is now continuing with the project 19ENV05 “Stable isotope metrology to enable climate action and regulation – STELLAR”. Selected commercial pure CO2 were used to prepare different CO2 reference materials in high pressure cylinders by using the gravimetric method, adapting the INRIM procedure applied to the preparation of CO2 in N2/synthetic air mixtures. Starting from these pure materials, CO2 mixtures in synthetic air at atmospheric amount fraction were prepared. The prepared mixtures were then sent to the Max Planck Institute for Biogeochemistry (MPI-BGC), for the validation of their isotopic values. A sampling system was set up for the preparation of the CO2 samples sent for validation, in order to minimise fractionation effects during the sampling. An appropriate uncertainty budget was developed for the reference mixtures, by taking into account all the relevant uncertainty contributions

Reference measurement system for low electrolytic conductivity values with a flowing solution

In order to answer the needs of the industrial and the clinical sectors, INRiM has undertaken activities to extend the traceability of electrolytic conductivity measurements to pure water values. In this progress report, the new cell and the measurement system with flowing solution are described. Since international documents prescribe the use of a system with flowing solution to reduce CO2 contamination for solutions with conductivity lower than 50 μS cm−1, preliminary measurements were carried out on three solutions with conductivity values of 50, 30 and 10 μS cm−1. Moreover, a comparison between a system with static solution and one with flowing solution was executed

Laboratory accreditation in Italy for reference solution production of sucrose in water

The accreditation of Chemifarm Srl laboratory for the calibration of two characteristics on the same aqueous solution has been achieved. The process has been executed by the Italian accreditation body for calibration laboratories (SIT). This is the first example of a producer of certified reference solutions in Italy. The solutions are mixtures of sucrose in water at several concentrations and are characterised for refractive index in the range of 1.33299 to 1.38115 and for mass fraction of sucrose in the range of 0 to 30 (commercially expressed in Brix degrees). Both traceability paths, obtained through efractometric and gravimetric methods, are reported. Furthermore, the paper describes the approach adopted to match the criteria based on ISO Guide 34 and ILAC-G 12, the documents with requirements for certified reference material producers, in compliance with those of ISO/IEC 17025, the norm for the laboratory accreditation

Comparison of gravimetry and dynamic dilution for the generation of reference gas mixtures of CO2 at atmospheric amount fraction

Carbon dioxide (CO2) is the most important greenhouse gas generated by human activities. Its concentration has been growing in the atmosphere reaching a current annual average of 410 μmol mol−1. Reliable determinations of the atmospheric CO2 concentration are of great importance for the development of models used in climate change predictions. The production of reference mixtures of known composition is a key step for the achievement of reliable data for the monitoring of greenhouse gases in atmosphere.The present work deals with a comparison of two methods for gas mixtures preparation, the first based on the gravimetric preparation of gas mixtures in high pressure cylinders and the second based on dynamic dilution, for generating gas mixtures at the desired amount fraction online.Reference mixtures of CO2 can be used for the calibration of monitoring sensors, with various applications ranging from environmental monitoring to industrial process control