Metrological traceability in gas analysis at I.N.Ri.M: gravimetric primary gas mixtures

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.     

Measurement uncertainty and doping control in sport. Part 2: Metrological traceability aspects

The assessment of (non-)compliance in doping control and in particular the appreciation of uncertainty of measurement in such an assessment has become a subject of debate. In a previous paper, the requirements for evaluating measurement uncertainty have been addressed. The debate now focuses on the estimation of the standard uncertainty. The completeness of an uncertainty budget is discussed in view of the (metrological) traceability of the result. It is concluded that despite the fact that the new doping rules dictate that A-tests and B-tests be performed in the same laboratory, the uncertainty budget should encompass all factors, including between-laboratory effects. The assessment of (non-)compliance should be based on a one-sided t-test. There is also consensus about the level of confidence to be applied (99%), despite the fact that the regulations state 95% as the appropriate level.     

Metrological traceability for benzo[a]pyrene quantification in airborne particulate matter

Airborne particulate matter (PM) represents one of the most important sources of urban pollution due to its physical and chemical properties. There is a great concern for PM dangerous effects on human health because particles can deeply penetrate into the respiratory system, carrying the contaminants adsorbed onto their surface. Polycyclic aromatic hydrocarbons (PAHs) are a class of organic contaminants that can be adsorbed onto PM and can have harmful effects on health, due to their particular chemical structure. The International Agency for Research on Cancer (IARC) classified PAHs as potential carcinogenic agents and benzo[a]pyrene (BaP) as carcinogenic to humans. In this paper, the development of a metrologically traceable procedure for the quantification of BaP in airborne PM, performed at the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.), is presented. The identification and quantification of BaP in PM samples were carried out by gas chromatography coupled with mass spectrometry (GC–MS). Metrological traceability was established in all the procedure steps, after performing the method validation. Suitable certified reference materials (CRMs) were used both to validate the analytical method and to calibrate the GC–MS. The measurement uncertainty was evaluated by identifying and taking into account all the relevant sources deriving from the whole procedure steps.     

Primary reference materials and traceability chain for gas composition

This article briefly describes research on the development of primary reference gases and the traceability system of gas measurement at the National Research Center for Certified Reference Materials, China.     

N. M. R. coupling constants

Approximate ab-initio calculations of NMR coupling constants are reported, for a number of small molecules. The agreement with experiment is erratic, and is shown to depend critically on the form of the excited state wavefunctions. This suggests that the use of an average energy approximation is far from valid.

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Zusammenfassung NMR Kopplungskonstanten werden für eine Anzahl von kleinen Molekülen mitgeteilt, wobei sich keine rechte Übereinstimmung mit dem Experiment ergibt. Es zeigt sich, daß die Werte kritisch von der Form der Wellenfunktion für die angeregten Zustände abhängen. Das läßt vermuten, daß die Verwendung eines mittleren Energienenners nicht zu empfehlen ist.

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Résumé Calculs ab-initio approchés des constantes de couplage NMR d'un certain nombre de petites molécules. L'accord avec l'expérience est erratique et dépend d'une façon critique de la forme des fonctions d'onde excitées. Ceci suggère que l'emploi d'une approximation d'«énergie moyenne» est loin d'être valable.

     

An interview with I.M. Kolthoff

Izaak Maurits Kolthoff was born in 1894, in Almelo, Holland. He studied pharmacy at the University of Utrecht, and was awarded a Ph.D. in chemistry there in 1918. He served as Conservator of the Pharmaceutical Institute at the University from 1917 to 1927 and as a privat docent (lecturer) from 1924 to 1927. In 1927 Professor Kolthoff began his long association with the University of Minnesota, serving as Professor and Chief of the Division of Analytical Chemistry until 1962 and since then as Professor Emeritus. He is a member of the United States National Academy of Sciences, a foreign member of the Royal Flemish Academy of Sciences and of a number of other learned Societies thoughout the world. He has, in the course of his long career, been given many awards. The latest of these is the Special Award of the Society for Analytical Chemists of Pittsburgh for 1981.     

FeMo cofactor of nitrogenase: a density functional study of states M(N), M(OX), M(R), and M(I).

The M(N) S = (3)/(2) resting state of the FeMo cofactor of nitrogenase has been proposed to have metal-ion valencies of either Mo(4+)6Fe(2+)Fe(3+) (derived from metal hyperfine interactions) or Mo(4+)4Fe(2+)3Fe(3+) (from M?ssbauer isomer shifts). Spin-polarized broken-symmetry (BS) density functional theory (DFT) calculations have been undertaken to determine which oxidation level best represents the M(N) state and to provide a framework for understanding its energetics and spectroscopy. For the Mo(4+)6Fe(2+)Fe(3+) oxidation state, the spin coupling pattern for several spin state alignments compatible with S = (3)/(2) were generated and assessed by energy and geometric criteria. The most likely BS spin state is composed of a Mo3Fe cluster with spin S(a) = 2 antiferromagnetically coupled to a 4Fe' cluster with spin S(b) = (7)/(2). This state has a low DFT energy for the isolated FeMoco cluster and the lowest energy when the interaction with the protein and solvent environment is included. This spin state also displays calculated metal hyperfine and M?ssbauer isomer shifts compatible with experiment, and optimized geometries that are in excellent agreement with the protein X-ray data. Our best model for the actual spin-coupled state within FeMoco alters this BS state by a slight canting of spins and is analogous in several respects to that found in the 8Fe P-cluster in the same protein. The spin-up and spin-down components of the LUMO contain atomic contributions from Mo(4+) and the homocitrate and from the central prismane Fe sites and muS(2) atoms, respectively. This qualitative picture of the accepting orbitals for M(N) is consistent with observations from M?ssbauer spectra of the one-electron reduced states. Similar calculations for the Mo(4+)4Fe(2+)3Fe(3+) oxidation state yield results that are in poorer agreement with experiment. Using the Mo(4+)6Fe(2+)Fe(3+) oxidation level as the most plausible resting state, the geometric, electronic and energetic properties of the one-electron redox transition to the oxidized state, M(OX), catalytically observed M(R) and radiolytically reduced M(I) states have also been explored.     

Conformation et spectrométrie de R.M.N.: II

The four isomeric 3-dimethylamino-trans-2-decalols-1,1,4,4-d₄ have been synthesised. Examination of PMR spectra of these compounds allows us to confirm the ‘flattened-chair’ conformation for the cis N(CH₃)₂^a OH^e isomer, whereas the remaining three conserve the double chair conformation. The same type of flattening is also observed in the case of the diaxial quaternary ammonium salt and is even more marked in the cis N(CH₃)₃^a OH^e isomer resulting in a ‘twist-chair’ conformation.     

Review: Authentication and traceability of foods from animal origin by polymerase chain reaction-based capillary electrophoresis

This work presents an overview of the applicability of PCR-based capillary electrophoresis (CE) in food authentication and traceability of foods from animal origin. Analytical approaches for authenticating and tracing meat and meat products and fish and seafood products are discussed. Particular emphasis will be given to the usefulness of genotyping in food tracing by using CE-based genetic analyzers.     

Equation of state for square-well chain molecules with variable range. I: Application for pure substances

An equation of state (EOS) for square-well chain molecules with variable range developed on the basis of statistical mechanics for chemical association in our previous work is employed for the calculations of pVT properties and vapor–liquid equilibria (VLE) of pure non-associating fluids. The molecular parameters for 73 normal substances and 46 polymers are obtained from saturated vapor pressure and liquid molar volume data for normal fluids or pVT data for polymers. Linear relations are found for the molecular parameters of normal fluids with their molecular weight of homologous compounds. This indicates that the model parameters of homologous series, subsequently pVT and VLE, can be predicted when experimental data are not available. The predicted saturated vapor pressures and/or liquid volumes are satisfactory through the generalized model parameters. The calculated VLE and pVT for normal fluids and polymers by this EOS are compared with those from other engineering models, respectively.     

Proton N.M.R. lineshape in nematic microdroplets

The dependence of the proton N.M.R. absorption spectrum on nematic director configuration and molecular self-diffusion in nematic submicrondroplets is analysed. The lineshape is evaluated numerically for radial and bipolar director configuration. The motional averaging is taken into account by means of a numerical simulation of the molecular diffusion which induces slow molecular reorientations due to non-uniform orientational ordering in the droplet. This diffusion process strongly affects the absorption spectra of the radial configuration, whereas spectra of the bipolar configuration are only slightly influenced. The possibility of determinating the submicrometre nematic droplet structures using the proton N.M.R. lineshape is discussed.     

29Si N.M.R. investigations of polysiloxanes

A number of side chain liquid crystal polysiloxanes prepared from both homo-and co-polymeric backbones have been studied by ²⁹Si N.M.R. and the chemical shifts assigned. Partly mesogenated poly(hydrogenmethylsiloxanes) have been similarly studied and chemical shift assignments made for sequence distributions. The data should prove helpful in studies of compositional variation in preparations of side chain copolymeric polysiloxanes.