The effect of collisions with nitrogen on absorption by oxygen in the a-band using cavity ring-down spectroscopy

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International Comparison EURO.QM-S5 / 1166: Carbon Dioxide Mixtures in Nitrogen Final report

This supplementary comparison is designed to test the capabilities of the participants to measure and certify carbon dioxide in nitrogen, and to provide supporting evidence for the CMCs of institutes for carbon dioxide. Indeed this comparison aims to demonstrate the capabilities of IPQ in the production of primary gas mixtures of carbon dioxide in nitrogen and for the participant laboratories to demonstrate their capabilities on certifying primary gas mixtures of percent levels of carbon dioxide in nitrogen

Advances in reference materials and measurement techniques for greenhouse gas atmospheric observations

We present the global research landscape which aims to deliver a measurement infrastructure to underpin atmospheric observations of key greenhouse gases governing changes in the Earth’s climate. These measurements present a significant challenge to the metrological community, analytical laboratories and major producers of reference materials. The review focuses on the progress made in the Gas Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM-GAWG) in establishing the primary realisation of the amount-of-substance fraction for carbon dioxide, methane and nitrous oxide in an air matrix. It also focuses on the importance of providing traceable measurements of isotopic composition of these components for commutability of reference materials and for isotope ratio measurements for greenhouse gas source attribution. The review examines the developments in the Global Atmosphere Watch (GAW) Programme of the World Meteorological Organisation (WMO) for providing the framework for the development and implementation of integrated greenhouse gas observations, which is vital for understanding the global carbon cycle and the role greenhouse gases play in climate change. The developments in analytical techniques are also discussed which have shaped the direction of the metrology required to meet the evolving and future needs of stakeholders

Physiological characterisation of acuB deletion in Aspergillus niger

The acuB gene of Aspergillus niger is an ortholog of facB in Aspergillus nidulans. Under carbon-repression conditions, facB is repressed, thereby preventing acetate metabolism when the repressing carbon source is present. Even though facB is reported to be repressed directly by CreA, it is believed that a basal level of FacB activity exists under glucose-repressive conditions. In the present study, the effect of deletion of acuB on the physiology of A. niger was assessed. Differences in organic acid and acetate production, enzyme activities and extracellular amino and non-amino organic acid production were determined under glucose-repressing and -derepressing conditions. Furthermore, consumption of alternative carbon sources (e.g. xylose, citrate, lactate and succinate) was investigated. It was shown that AcuB has pleiotropic effects on the physiology of A. niger. The results indicate that metabolic pathways that are not directly involved in acetate metabolism are influenced by acuB deletion. Clear differences in organic acid consumption and production were detected between the a dagger acuB and reference strain. However, the hypothesis that AcuB is responsible for basal AcuA activity necessary for activation of acetate metabolic pathways, even during growth on glucose, could not be confirmed. The experiments demonstrated that also when acuB was deleted, no acetate was formed. Therefore, AcuB cannot be the only activator of AcuA, and another control mechanism has to be available for activating AcuA

CCQM-K131 Low-polarity analytes in a multicomponent organic solution: polycyclic aromatic hydrocarbons (PAHs) in acetonitrile

Solutions of organic analytes of known mass fraction are typically used to calibrate the measurement processes used to determine these compounds in matrix samples. Appropriate value assignments and uncertainty calculations for calibration solutions are critical for accurate measurements. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims (CMCs) made by national metrology institutes (NMIs) and designated institutes (DIs). To enable NMIs and DIs to update or establish their claims, in 2015 the Organic Analysis Working Group (OAWG) sponsored CCQM-K131 "Low-Polarity Analytes in a Multicomponent Organic Solution: Polycyclic Aromatic Hydrocarbons (PAHs) in Acetonitrile". Polycyclic aromatic hydrocarbons (PAHs) result from combustion sources and are ubiquitous in environmental samples. The PAH congeners, benz[a]anthracene (BaA), benzo[a]pyrene (BaP), and naphthalene (Nap) were selected as the target analytes for CCQM-K131. These targets span the volatility range of PAHs found in environmental samples and include potentially problematic chromatographic separations. Nineteen NMIs participated in CCQM-K131. The consensus summary mass fractions for the three PAHs are in the range of (5 to 25) μg/g with relative standard deviations of (2.5 to 3.5) %. Successful participation in CCQM-K131 demonstrates the following measurement capabilities in determining mass fraction of organic compounds of moderate to insignificant volatility, molar mass of 100 g/mol up to 500 g/mol, and polarity pKow < −2 in a multicomponent organic solution ranging in mass fraction from 100 ng/g to 100 μg/g: (1) value assignment of primary reference standards (if in-house purity assessment carried out), (2) value assignment of single and/or multi-component organic solutions, and (3) separation and quantification using gas chromatography or liquid chromatography