Temperature dependence of magnetic neutron scattering by dislocations. II

Magnetic small-angle scattering of neutrons by dislocations has been investigated in a plastically deformed nickel single crystal between 300 and 540K. By proper adjustment of the magnetic field strength the range of magnetic disturbance around dislocation lines, i.e. the magnetic exchange length, could be held fixed at 16.5 nm for all temperatures. The experimental results are compared to calculations based on micromagnetic theory.     

Estimation of the measurement uncertainty of the high-performance anion-exchange chromatographic determination of carbohydrates in soluble (instant) coffee

The measurement uncertainty of the determination of free and total carbohydrates in soluble (instant) coffee using high-performance anion exchange chromatography with pulsed amperometric detection according to AOAC Method 995.13 and ISO standard 11292 was calculated. This method is important with regard to monitoring several carbohydrate concentrations and is used to assess the authenticity of soluble coffee. We followed the recommendations of the ISO, Eurachem, and Valid Analytical Measurement (VAM) guides: individual uncertainty contributions u(x) were identified, quantified, and expressed as relative standard deviations related to each specific source u(x)/x or RSD(x). Eventually, they were combined to yield the standard uncertainty and the relative standard uncertainty of a given carbohydrate concentration, c, that is respectively u(c) and u(c)/c. As a result of our study, we could demonstrate that the overall repeatability of the carbohydrate determination in duplicate, RSD(r); the repeatability of the integration of the peak area of the carbohydrate standards, RSD(r(area)(ST)); and the uncertainty of the linear calibration model used in our laboratory, RSD (linST), are the most significant contributions to the total uncertainty. The u(c)/c values thus determined differ for each carbohydrate and depend on their concentrations. The least standard uncertainties that can be achieved are about 2.5%. The question of trueness in the total carbohydrate assay (determination of monosaccharides obtained upon hydrolysis of coffee oligo- and polysaccharides) was addressed. For this purpose, we analyzed the data of 2 different collaborative trials in which our laboratory took part.     

Evaluation of three calibration methods to compensate matrix effects in environmental analysis with LC-ESI-MS

In quantitative analysis of environmental samples using high-performance liquid chromatography–electrospray ionization mass spectrometry (HPLC-ESI-MS) one of the major problems is the suppression or, less frequently, the enhancement of the analyte signals in the presence of matrix components. Standard addition is the most suitable method for compensating matrix effects, but it is time-consuming and laborious. In this study we compare the potential of three calibration approaches to compensate matrix effects that occurred when seven analytes (naphthalene sulfonates) were quantified in time series samples of waters with different matrices (untreated and treated industrial wastewater). The data obtained by external calibration, internal calibration with one standard, and external sample calibration (corresponding to matrix-matched calibration) were compared with those obtained by standard addition. None of the three approaches were suitable for a sample series of highly loaded, untreated wastewater with highly variable matrix. For less heavily loaded and less variable samples (treated wastewater effluents), the external sample calibration provided reasonable results for most analytes with deviations mostly below 25% as compared to standard addition. External sample calibration can be suitable to compensate matrix effects from moderately loaded samples with more uniform matrices, but it is recommended to verify this for each sample series against the standard addition approach.     

Polarographische Untersuchungen in wasserfreiem Äthylendiamin

Es werden die Halbwellenpotentiale von Alkali- und Tetraalkylammoniumionen sowie des Sauerstoffes in wasserfreiem Äthylendiamin gegen eine wäßrige Normalkalomelektrode bestimmt und die Einflüsse von Leitsalz und Anion studiert.     

Magnetic-dipole hyperfine structure in 4d- and 5d-shell atoms

The magnetic-dipole hyperfine interaction constantsA of low-lying metastable atomic levels in⁹¹Zr,¹⁸¹Ta,¹⁸³W, and¹⁹¹Ir determined from atomic-beam magnetic-resonance investigations are analyzed with respect to the effective-operator formalism. Similar results for other 4d- and 5d-shell atoms are also tabulated. The experimental results for the effective 〈r ^?3〉 values are compared with relativistic predictions for the 4d ^N 5s and 5d ^N 6s ² series.