The research activity is related to inorganic and organic chemistry, gases, electrochemistry and bio-analysis. Analytical procedures for trace metals and organic compounds are developed and tested. The gravimetric method and laser spectroscopy procedures are developed and applied for the primary standards preparation of different gas mixtures. Methods based on spectroscopy measurements are under investigation for bioanalysis in biochemical studies. Most of the results are obtained in the framework of international joint research programs promoted by CIPM, EUROMET and EURACHEM. On this basis, applied researches in environmental, toxicological and medical related problems are also in progress.

The activity carried out deals with the preparation of primary gravimetric gas mixtures, gas analysis and organic analysis. Some primary mixtures of CO₂ at atmospheric concentration in matrices of nitrogen and air were prepared with the gravimetric method. The mixtures were in the range (330-390) µmol mol^-1 with a relative standard uncertainty of 0.1%. As a consequence, for the first time it was possible to take part in an international key comparison CCQM-K52. The NDIR analyser used for this comparison was calibrated by means of three primary mixtures prepared at INRIM and validated with respect to other certified reference gas mixtures of similar composition. The analytical activity on gas mixtures of CO and CO₂ at emission level continued and it was possible to also take part in EUROMET project 883 on automotive emission. A first pair of gravimetric primary mixtures of CO₂ in nitrogen at emission level, in the concentration around 12% mol mol^-1 with a standard uncertainty of some µmol mol^-1, was prepared. A new research line on nitrogen oxides (NO_X) started. A dedicated chemiluminescence analyser was characterised as a starting point for a feasibility study on the preparation of gravimetric mixtures of NO and NO₂ in matrices of nitrogen and air. As for organic analysis, some steps were carried out towards the establishment of a correct traceability chain for the determination of polychlorinated biphenyls in organic solutions.

Chemiluminescence analyser for the determination of nitrogen oxides (NO_x).

The research activity mainly addressed the development and application of radioanalytical (Neutron Activation Analysis) and spectrochemical (Graphite Furnace-Atomic Absorption Spectroscopy) techniques employed in trace elements studies. Within the framework of the activities of the IAWG of the CCQM, INRIM participated in several key and pilot interlaboratory comparisons. Environmental, toxicological and technological materials were investigated as Reference Materials (RMs) in collaboration with NIST (USA), IAEA (ONU) and IRMM (EU). In the field of applied research, the activity focused on atmospheric pollution related problems (indoor, urban, remote areas, biomonitors) as well as on neurodegenerative diseases (Parkinson). This last research was accomplished in collaboration with the CNR Institute of Biomedical Technology.
A collaboration with ENI has been carried out in the field of environmental monitoring. The research was focused on the evaluation of toxic metals pollution in different areas of Kazakhstan near the Caspian sea.

Results of the Key Comparison CCQM-K43 on the determination of Se in a complex matrix (salmon).

The use of optical spectroscopy for the development of new standards and measurement techniques in the fields of the environment and of health is a challenge for metrology in the near future. Urgent research needs, where the standard based on spectroscopy is more interesting, concern global climate change monitoring and the measurement of the concentration of species regulated by the Kyoto protocol and directives for air quality. Concerning metrological research for quantitative diagnostics, the validation of new fluorophores, the base for the realization of reference materials for optical imaging and fluorescent microscopy is a key problem.
With the aim of developing reference gas standards at trace level based on the absolute measurements of the linestrength of molecular transitions, experiments have been carried out for the generation of VOC in traces in air in suitable cells. The physical-chemical surface composition of the cell walls and the development of thermo-chemical decomposition methods for VOC generation have been studied.
Concerning air quality standards, the uncertainty of ozone in the air standard has been ameliorated with a new model that takes into account temperature gradients measured in the gas. A new laboratory for the calibration of ozone analyzers/calibrators has been realized. A co-operation INRIM-APAT has been signed for the setting-up of reference laboratories throughout Italy.
Concerning methods and reference materials for bio-imaging, investigation has begun into fluorescent nanoparticle behavior (ZnS/CdSe Quantum dots at 565 nm) by emitted power and by dimension. An optical system has been set up and a suitable procedure for TEM imaging, avoiding particle aggregation, has been defined.

ZnS/CdSe Quantum Dots fluorescence at 565 nm excited with a violet laser. Measured nanoparticle dimension of 3.2 nm from TEM image.

The potentiometric measurement of pH has been further assessed by evaluating and comparing the behaviour of primary (Harned cell) and secondary (glass electrodes) apparatus applied to measure primary standards (e.g. 0.01 mol kg^-1, tetraborate buffer) or reference solutions resembling natural fluids (e.g. artificial seawater samples). In all cases, it was shown that the evaluation of ionic strength, I, of the solution is a dominant factor: slight modification in the value of I used to compute the activity coefficient of a single ion, γ_i, in the calculation of pH from the acidity function, can significantly affect the reference value of the calibrator tool. This is true, in particular, for low ionic strengths; an approximate value of I then can cause distortions along the pH traceability chain. As for salt rich aqueous samples, although they do not allow for a straightforward metrological character because of the lack of stability, careful procedures for measurements and calculation can be adopted to attain comparable primary and secondary pH values. Effects associated with measurement procedures and manipulation of the samples, which are deleterious to pH constancy, can be rationalised and corrected in the calculations.

First results have been obtained in the development of an electrochemical apparatus for the determination of the dissolved oxygen (DO) in aqueous solutions, a project conducted in cooperation with the University of Gent (Belgium) and the Università di Torino. The measurement method is based on an amperometric cell designed on the model of Clark-type sensors and represents the first attempt at the definition of the traceability of DO concentration values. This sensor shows good linear response (R = 0.98) in the range between 1 and 11 mg L^-1 of DO concentration. A preliminary analysis of the apparatus revealed difficulties associated with its calibration, due to the difficulty of reproducing the experiments with DO amount accurately controlled thanks to gas bubbling in the solution. Improvements are expected from a different preparation method of calibration solutions. Possible ways are the catalytic decomposition of metallic peroxides or the electrochemical generation of oxygen via the coulometric technique. The latter would make it possible to prepare the solutions and characterise them simultaneously, bringing about a lower measurement uncertainty.

Amperometric cell for the measurement of dissolved oxygen concentration (Gent University).