Reference materials for nutrition research

Summary The importance of the accuracy of analytical data of nutritional relevance and the effect of the use of relevant reference materials in nutrition research are discussed. The needs of the nutritionist for reference materials are outlined with regard to the elements of interest, the substrates of interest and the chemical species of elements.     

Functional ceramic materials database: an online resource for materials research

We present work on the creation of a ceramic materials database which contains data gleaned from literature data sets as well as new data obtained from combinatorial experiments on the London University Search Instrument. At the time of this writing, the database contains data related to two main groups of materials, mainly in the perovskite family. Permittivity measurements of electroceramic materials are the first area of interest, while ion diffusion measurements of oxygen ion conductors are the second. The nature of the database design does not restrict the type of measurements which can be stored; as the available data increase, the database may become a generic, publicly available ceramic materials resource.     

Reference materials for small-sample analysis

Many modern analytical techniques use small solid samples and lack proper reference materials for their calibration and quality assurance. A remedy to this deficiency may be in the development of a new genre of highly homogeneous natural matrix materials, their properties being studied with analytical techniques such as PIXE and μ-PIXE, solid sampling AAS, scanning electron microscopy in combination with electron probe X-ray microanalysis, and INAA. Suitable natural materials may be obtained in form of single cell biological materials, finely dispersed suspensions and precipitates such as air particulate matter or sediments, and by appropriate particle size reduction of complex matrices. Initial studies have been carried out on single cell green algae biomass and air particulate matter, as well as several processed materials. Narrow particle size distributions with particles preferably below 10 μm diameter may assure the desired analytical homogeneity. The determination of sampling parameters for individual measurands will ascertain the utility of a material for small-sample analysis. Received: 16 June 1997 / Revised: 24 September 1997 / Accepted: 27 September 1997     

Certified reference materials for thermal analysis

Eight inorganic substances recommended by ICTA as temperature standard reference materials for DTA and DSC were studied: KNO₃, KClO₄, Ag₂SO₄, K₂CrO₄, quartz, K₂SO₄, BaCO₃ and SrCO₃. The content of pure component in each of these substances was determined by classical chemical analysis. The temperatures and the heats of polymorphic transformations of these substances were measured with a Perkin-Elmer DSC-2 differential scanning calorimeter, and DTA studies were performed on a MOM 1500 D Q-derivatograph. The plot heat of transformation by DSCvs. DTA peak area is advanced as a calibration line for the approximate estimation of quantitative DTA effects. The substances studied will be certified as temperature standard reference materials for use in DTA and DSC.

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Zusammenfassung Acht von der ICTA als Temperaturstandard-Referenzmaterialien für DTA und DSC empfohlene und im Lande verfügbare Substanzen wurden untersucht: KNO₃,KClO₄, Ag₂SO₄, K₂Cr₂O₄, Quarz, K₂SO₄, BaCO₃ und SrCO₃. Der Gehalt der Substanzen an diesen Verbindungen wurde klassisch chemisch-analytisch bestimmt. Temperaturen und Enthalpien der polymorphen Umwandlungen wurden mit dem Gerät DSC 2 (Perkin-Elmer) bestimmt, DTA-Untersuchungen erfolgten mittels Derivatograph Q 1500 D (MOM). Eine Darstellung (Umwandlungsenthalpie aus DSC-Messung) über der DTA-peak-Flä-che wird als Eichgerade für die näherungsweise quantitative Bewertung der DTA-Effekte vorgeschlagen. Die genannten Substanzen sollen als Temperaturstandards für DTA und DSC geprüft werden.

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Rapeseed reference materials for glucosinolate analysis

Summary The use of rapeseed cake is limited by the presence of a number of antinutritional factors the most important of which are glucosinolates. Introduction by EEC of a premium to produce rapeseed with low glucosinolate content has brought the need for reference material and accurate official methods of analysis. This paper summarises the work, begun at the end of 1987, to prepare three batches rapeseed materials (cleaning, mixing and packaging) for an intercomparison of methods. Details are presented of homogeneity and stability studies and the results of the intercomparison are discussed. One of the batches was prepared in sufficient quantity to serve as a reference material and the reference value for the total glucosinolate content of this sample was obtained from the results of the intercomparison.

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Rapssamen-Referenzmaterial für die GlucosinolatanalyseEntwicklung von Rapeseed BCR RM 190 und Ergebnisse eines Ringversuchs

     

NMR Imaging and materials research

The use of nuclear magnetic resonance in materials research is elaborated. While NMR applications to materials are discriminated between rigidly solid, rubbery, and liquid matter, NMR methods are divided into spectroscopy and imaging. The connections between the different material and NMR categories are explained. Particular emphasis is placed on NMR with spatial resolution, which is illustrated by examples from imaging of solid polymers and elastomers.     

Distribution patterns of rare-earth elements in biological materials evaluated by radiochemical neutron activation analysis

This study deals with the quantitative determination of eight REE's viz, La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu as an Integral part of a post-irradiation chemical separation scheme for the determination of 14 trace elements in biological materials. REE values are given for NBS Orchard Leaves SRM 1571, NBS Bovine Liver SRM 1577 and Bowen's Kale, as well as for some other biological (reference) materials of plant, animal and human origin. Chondritic-normalized REE patterns of these materials are discussed. It is shown that differentiations in REE-pattern between soil and plant may occur, and also that within the human body different modes of fractionation of REE's take place.     

Temperature standard reference materials for thermal analysis

The feasibility of the use of potassium nitrate and potassium perchlorate as temperature standards in Differential scanning calorimetry has been studied. The solid-state phase transition temperatures of KNO₃ and KClO₄ were determined by means of DSC. The metrological properties of these salts as calibration materials were examined. The reliability of KNO₃ and KClO₄ calibrations was investigated by twofold determination of the bismuth melting temperature after the apparatus had been calibrated with indium and lead, and with KNO₃ and KCl_O4. Conclusions were drawn concerning the suitability of these salts for use as DSC temperature calibrants.

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Zusammenfassung Es wurde die Möglichkeit der Verwendung von Kaliumnitrat und Kaliumperchlorat als Temperaturstandard für DSC untersucht. Die Bestimmung der Temperaturen für Feststoff-Phasenumwandlungen von Kaliumnitrat und Kaliumperchlorat wurde mittels DSC erreicht. Weiterhin wurden die meßtechnischen Eigenschaften der untersuchten Salze (KNO₃ und KClO₄) als Bezugssubstanzen geprüft. Die Zuverlässigkeit der Kalibrierung mittels KNO₃ und KClO₄ wurde durch eine zweifache Bestimmung der Schmelztemperatur von Wismut überprüft: einmal nach der Kalibrierung des Gerätes mit Indium und Blei und andererseits nach der Kalibrierung mit Kaliumnitrat und Kaliumperchlorat. Angesichts der Resultate kann man feststellen, daß die untersuchten Salze zur Temperaturkalibrierung in der DSC geeignet sind.

     

Development of reference materials for microbiological analysis

The reliability of reference materials (RMs) depends on properties such as fitness, robustness, commutability, stability and homogeneity. The development of RMs for microbiological analysis is especially challenged through questions around the stabilisation and recovery of viable cells, the dispersion of precise numbers of cells, matrix effects and, when using molecular techniques, the presence of nucleic acids (e.g. DNA) of dead and live target organisms. However, RMs are indispensable tools for quality control in microbiological analysis. The Institute for Reference Materials and Measurements (IRMM), as part of the European Commission, concentrates its efforts on the development of RMs to support the development, implementation and monitoring of EU legislation. A special focus is given to highly precise RMs for presence/absence and enumeration tests in microbiological food and water analysis. Another group of new RMs certified by the IRMM comprise DNA-based materials to control the identity of micro-organisms in qualitative assays. All of these activities serve to improve quality control in microbiological analysis. Presented at ‘BERM-10’, April 2006, Charleston, SC, USA.     

Wooden-based materials: Eco-friendly materials for direct mass spectrometric analysis and microextraction

Lignocellulosic materials have arisen as a sustainable alternative in microextraction techniques during the last 10 years. As they are natural materials, their use fits into some of the principles of Green Analytical Chemistry. Their inherent porosity, narrow shape, and rigidity permit their use in ambient ionization mass spectrometry techniques. In particular, the combination of wooden-based materials and direct analysis gives birth to the so-called wooden-tip electrospray ionization mass spectrometry technique. This approach has been used for the direct analysis of complex samples, and as a streamlined tool for fingerprint quality analysis. Also, wooden-based materials can be superficially modified to boost the interaction with target compounds, allowing their isolation from complex samples. This review describes the potential and applicability of direct analysis using lignocellulosic materials, as well as other alternatives related to their use in microextraction.     

Thermal expansion behaviour — Limits and possibilities for materials research

In the field of materials research thermal expansion plays an important role not only in the case of applications at higher temperatures but also in connection with the preparation of the materials themselves.For porous materials produced by powder metallurgical techniques the sintering process leads to a shrinkage or an expansion of the material during its preparation. From the investigation of the shrinkage or the expansion behaviour new conclusions can be drawn concerning the interpretation of solid or liquid state reactions which allow an improvement of the materials properties.

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Zusammenfassung Auf dem Gebiet der Materialforschung spielt die Messung der thermischen Ausdehnung eine grosse Rolle sowohl für die Anwendung bei hohen Temperaturen als auch im Zusammenhang mit der Präparation des Materials.Bei porösen Materialien, die nach pulvermetallurgischen Methoden hergestellt werden, ist der Sinterprozess von einem Schrumpfen oder einer Ausdehnung des Materials begleitet. Die Untersuchung dieser Vorgänge liefert neue Ergebnisse zur Deutung von Flüssigoder- oder Festphasenreaktionen und damit Möglichkeiten zur Verbesserung der Materialeigenschaften.

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Pattern recognition for the analysis of polymeric materials

A new method of polymer classification is described involving dynamic mechanical analysis of polymer properties as temperature is changed. The method is based on the chemometric analysis of the damping factor (tan delta) as a function of temperature. In this study four polymer groups, namely, polypropylene, low density polyethylene, polystyrene and acrylonitrile-butadiene-styrene, each characterised by different grades, were studied. The aim is to distinguish polymer groups from each other. The polymers were studied over a temperature range of -50 degrees C until the minimum stiffness was reached, tan delta values were recorded approximately every 1.5 degrees . Principal components analysis was performed to visualise groupings and also for feature reduction prior to classification and clustering. Several clustering and classification methods were compared including k-means clustering, hierarchical cluster analysis, linear discriminant analysis, k-nearest neighbours, and class distances using both Euclidean and Mahalanobis measures. It is demonstrated that thermal analysis together with chemometrics provides excellent discrimination, representing a new approach for characterisation of polymers.     

Development of food reference materials for nutritional analysis

Summary The development of five reference materials for major nutritional properties, whole milk powder, pork muscle, wheat and rye flour, and haricots verts beans is described. Homogeneity and stability of these materials proved to be adequate. A preliminary intercomparison of methods showed that results for total fat and total dietary fibre were method dependent. Evaluation of methods used for available carbohydrates revealed poor solubilisation and hydrolysis of starch in some laboratories. This intercomparison has given valuable information for the final certification of these materials.