The ETACS European project for testing the comparability of sensors and analysers

ETACS is the official acronym for the European project "European Testing and Assessment of Comparability of On-line Sensors/Analysers". This project has three main objectives to achieve the comparability of performance data for sensors and analysers in the environmental field. First, to develop a test protocol for validation and comparison of the performance of on-line sensors/analysers. The test protocol is intended to be generic, that is independent of the specific sensors/analysers and the specific parameters to be monitored. Second, the practical testing of this test protocol to assess its applicability and to develop the techniques used. Finally, to achieve widespread acceptance of the test protocol by producer/suppliers, users and relevant authorities to assist its early adoption as an agreed European standard. Laboratory tests for producing the test protocol have been carried out and completed to check the applicability of such a protocol.     

Separation and determination of alditols and sugars by high-pH anion-exchange chromatography with pulsed amperometric detection

Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic-pulsed amperometric detection (HPAEC-PAD) method that determines all the polyols used as food additives in food products and the most commonly found mono- and disaccharides on a routine basis. The linearity, repeatability, internal reproducibility and accuracy are described. The applicability of the method has been demonstrated by the analysis of 46 relevant samples and by participation twice in the Food Analysis Performance Assessment Scheme (FAPAS) testing programme for food additives.     

Can the highest occupied molecular orbital of the uranyl ion be essentially 5f?

Recent relativistic calculations on the uranyl ion suggest that the low wave numbers of the first electron transfer bands are due to a bonding 5f-like orbital containing the two loosest bound electrons. Comparison with UF₆ makes it more likely that if indeed σ_u (and not π_u) is the highest occupied MO, it is rather due to “pushing from below” by U 6p (like N 2s in N₂).     

Theoretical analysis of the electronic structure and molecular properties of thioborine,HSB and comparison with related compounds. An ab initio mo-cal

Ab initio calculations on the thioborine molecule have been performed. Ionization potentials, force constants and geometry parameters are calculated in fair agreement with experimental values. A preliminary investigation of the sensitivity by nucleophilic attack has also been performed, indicating a rather strong tendency to undergo that type of reaction.     

Magnetic field dependence of the spin—spin relaxation time of ferric ions in Fe(NO3)3·9H2O and in frozen aqueous solutions

The electronic relaxation of ferric ions in Fe(NO₃)₃·9H₂O and in frozen aqueous solutions has been investigated by use of Mössbauer spectroscopy. The application of an external magnetic field causes a pronounced increase of the spin—spin relaxation time, an effect which is contrary to that normally found in ferric compounds. An explanation is given based on a difference in the ionic state energies of the neighbouring ions induced by the applied magnetic field.     

Rationalisation of weak ferromagnetism in manganese(III) chains: the relation between structure and ordering phenomena

The synthesis, structure and magnetic properties of the one-dimensional chain compounds [Mn(cyclam)(SO4)]ClO4.H2O (1) and [Mn(cyclam)(HCOO)](CF3SO3)(ClO4) (2) are reported. Cyclam is the cyclic tetradentate ligand 1,4,7,11-tetraazacyclotetradecane. Both chain compounds exhibit antiferromagnetic interactions within the chains. A magnetic ordering phase transition at 5.5 K in (1) is investigated by magnetisation measurements along the three principal crystallographic axes of a single crystal and the results show unambiguously that the ferromagnetic ordering is only taking place along one crystallographic axis. The spin structure of the magnetic ordered phase and the magnitude of the ferromagnetic moment are correlated with the crystal structure and symmetry of the compound.     

Pyrazine-2,3-dicarbonitriles substituted with maleimide derivatives

Syntheses and spectroscopic characteristics are reported for eight pyrazine-2,3-dicarbonitriles substituted with maleimide residue in addition to phenyl, 2-thienyl, or 2-furyl substituent. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1409–1414, September, 2007.     

A0-contractivity of the variable-step BDF's of order less than four

We construct a polyhedral norm in which the fixed-step backward differentiation formulas of order one to three are contractive when applied to any differential equation of the formy=(t)y, (t) 0 (i.e. A₀-contractive). The result also holds for non-uniform step-sequences if combined with certain restrictions on the stepwise order-selection.     

Electrospray ionization mass spectrometry fingerprinting of whisky: immediate proof of origin and authenticity

Authentic samples of whisky produced in Scotland and USA and counterfeit whisky samples commercialized in Brazil have been directly submitted to electrospray ionization mass spectrometry (ESI-MS) analysis in both the negative and positive ion modes to assess the potential of this technique for simple and rapid quality control and proof of authenticity of whisky samples. ESI in the negative ion mode yields the most characteristic whisky fingerprinting mass spectra in just a few seconds by direct infusion of the samples, detecting the most polar or acidic components of each sample in their deprotonated anionic forms. No pre-treatment of the sample, such as extraction or derivatization or even dilution, is required. The analysis of the ESI(-)-MS data both by simple visual inspection but more particularly by chemometric data treatment enables separation of the whisky samples into three unequivocally distinct groups: Scotch, American and counterfeit whisky, whereas single malt and blended Scotch whiskies are also distinguished to some extent. As indicated by ESI-MS/MS analysis, the diagnostic anions are simple sugars, disaccharides and phenolic compounds. Direct infusion ESI-MS therefore provides immediate chemical fingerprinting of whisky samples for type, origin and quality control, as demonstrated herein for American, Scottish and counterfeit samples, whereas ESI-MS/MS analysis of diagnostic ions adds a second dimension of fingerprinting characterization when improved selectivity is desired.     

Procedure for background estimation in energy-dispersive X-ray fluorescence spectra

A method for semi-automatic background estimation in energy-dispersive x-ray fluorescence spectra is outlined. Two cubic splines were investigated and the spline called the Butland interpolant was chosen for further investigation. Prior to the calculation of the spline, peak regions are set up, and suitable knots are defined outside the peak regions. To set up the peak regions, an automatic peak-search routine and a calibration equation are used. For a given peak, the latter relates the full width at half maximum (FWHM) to the peak centre. In turn, the size of the peak regions are defined by the FWHM multiplied by a constant given by the user. The method was tested on several types of spectra. It was found that the optimal size of the peak region decreased with increasing peak density. Reproducibility tests showed that the standard deviation of the summation of counts within a peak region and after background subtraction was less than would be expected from the counting statistics.