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  • Articles  (2,021)
  • 1995-1999  (1,011)
  • 1920-1924  (1,010)
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  • Articles  (2,021)
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  • 1
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Significant progress has been made with the introduction of new AOAC INTERNATIONAL programs since plans were announced at BERM-5 in Aachen, Germany. The AOAC® Technical Division on Reference Materials has been formed, the AOAC® Peer-Verified Methods Program has been established and ready to accept methods for study, and the AOAC® Test Kit Performance Testing Program has become operational.
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Primary, secondary and tertiary reference materials (RM) play an important role in quality controls of analytical measurements. Logistics of preparation and proper use of primary and secondary RMs are presented. Tertiary (i.e. in-house) control materials are useful as substitutes in the absence of recognized primary or secondary RMs. The lack of interdisciplinary interaction during development of RMs (e.g. in specific areas such as foods), has an important impact on limiting the usefulness of certain types of RMs. The abundance of RMs in some countries and regions appears to have little effect on the existing paucity in RMs in other regions, and the underlying causes are outlined. The ability of a laboratory to produce good quality in-house RMs traceable to recognized primary or secondary RMs is a direct measure of its quest for reliable analytical data. Therefore many laboratories should be encouraged to engage in secondary and tertiary RM activities designed to answer specific measurement problems. In this context, assistance (e.g. practical training opportunities) in identifying simple methods of analyses for their efficacy in determining specific analytes is a source of help that can be extended to countries experiencing limitations in laboratory instrumentation.
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The analytical strategy for the elemental chemical characterization of biological reference materials followed during a recently completed Reference Material development endeavour is discussed. Characterization, the assignment of reliable values to total elemental concentrations of a wide range of elements, poses the most difficult challenge in the scheme of reference material (RM) production. A review is presented of the many factors considered that significantly impinged on the conduct and outcome of the complex analytical characterization exercise. Major considerations were: (1) analytical elemental characterization philosophy, (2) analyte selection, (3) selection of analytical methodologies, (4) statistical protocols, (5) in-house characterization, (6) assessment of material homogeneity (7) cooperative interlaboratory characterization campaign, (8) data evaluation and (9) calculation of concentration values and associated uncertainties.
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  • 4
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The IAEA-331 spinach material NIST SRM 1570a Spinach Leaves, submitted to an intercomparison run by the IAEA, has been analysed by k0-based INAA with counting using both low and high energy photon detectors. The results have been compared with (i) the certified values of the NIST SRM 1570a; the agreement is good, taking into account the uncertainties; and (ii) the certified and “consensus” values of the former NIST SRM 1570 Spinach Leaves, their composition in minor and trace-elements are quite similar; however a lower content has been observed for Co, Fe and Sc in the IAEA-331 and for Zn in the SRM 1570. For quality control, the NIST 1573 Tomato Leaves and the NIST 1575 Pine Needles have been analysed using the same conditions as for the IAEA-331. The results agree quite well with the certified and “consensus” values given in the literature.
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  • 5
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Results obtained in interlaboratory comparisons on candidate reference materials Bovine Kidney and Bovine Muscle, in which more than 32 laboratories participated employing atomic spectrometry, electrochemical, and nuclear analytical techniques, have been evaluated using combined statistical and analytical considerations. Certified and/or information values for the elements Br, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, P, Pb, Rb, Se, and Zn have been established. Information on contents of the elements Al, As, Au, Cs, Li, Ni, Sb, Sn, Sr, and V is also presented.
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  • 6
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A proposed infant formula SRM 1846 has been analyzed for zinc, selenium and chromium by isotope dilution mass spectrometry (IDMS). The precision of the IDMS methods has been sufficient to allow the estimation of the sample homogeneity with respect to these three analytes. Overall means of 60.9±0.9 μg Zn/g (mean±standard deviation) and 76.1±1.9 ng Se/g have been found for 30 determinations. Values for chromium content have been found to depend on the sample preparation method, suggesting possible contamination. Accurary of the zinc, chromium and selenium values has been verified using a certified reference material, SRM 1549 “Non-Fat Milk Powder”.
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In Central Europe, the iodine content of weathered soils of new red sandstone, Muschelkalk, keuper and lower strata of new red sandstone, which developed from marine sediment is low. Boulder clays and diluvial sands also exhibit low iodine concentrations. In the same areas, the iodine concentration of drinking water decreases from 9 to 1 μg/l with increasing distance from the oceans. Cereals and foodstuffs produced from them are extremely iodine-poor. The iodine content of plants increases with the proportion of leaves. Soil contamination raises the iodine content of foodstuffs and improves the iodine supply of animals. The iodination of mineral mixtures increased the iodine content of cow's milk from 17 to 81 μg/l. The iodination of packed cooking salt and of the mineral mixtures for cattle and pigs resulted in a mean increase of the iodine intake of adults from about 30 μg/day to 48 and 59, respectively. Although iodine intake remained considerably below the calculated requirement for adults (100 to 150 μg/day), it led to the disappearance of Struma konnata and reduced the frequency of struma in children.
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  • 8
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A worldwide laboratory intercomparison was organized by the International Atomic Energy Agency's Analytical Quality Control Services (AQCS) involving the determination of trace elements in plant materials used for human consumption. The National Institute of Standard and Technology (NIST) Standard Reference Materials Program donated 5 kg of spinach designated for the production of the future Standard Reference Material SRM 1570a to this intercomparison; the AQCS provided a similar amount of cabbage. For the study, 150 units of each material were distributed and 114 laboratories reported results on both materials to AQCS. The results for the spinach, encompassing more than forty elements, have been compiled and evaluated; estimates of the elemental concentrations were made based on statistical evaluations, principles of analytical procedures and the laboratory performance indicated by the results on the cabbage material. Satisfactory estimates were obtained for 27 elements. Comparison with IAEA laboratory and NIST reference data did not reveal any significant bias that might have been introduced by the intercomparison approach or its evaluation.
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  • 9
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two international intercomparisons on the determination of trace elements in geological-environmental materials as well as two similar intercomparisons with biological materials provided a large amount of data elucidating the relative significance of various analytical techniques in the process of certification. The data have been investigated concerning their frequency of use, agreement of results by various techniques, percentage of outliers and general performance of the methods. Because many laboratories supplied results for both biological materials and both materials of mineral origin, the analysis of data in the form of two-sample charts has also been presented. The significance of an adequate procedure for outlier rejection for the proper assigning of certified values is emphasized and the unique role of neutron activation analysis in the certification process has been demonstrated. The use of highly reliable (“definitive”) methods for the verification of recommended values has been demonstrated.
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  • 10
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A pilot project was initiated to study the feasibility of preparing milk as a candidate reference material for 14C near environmental levels. Two materials, MK-B at natural level of 14C and MK-C4 at an elevated level, have been prepared from pasteurized 2% dairy milk. MK-C4 was spiked with an appropriate amount of 14C-methylated casein tracer to achieve the elevated level. Several samples from MK-B and MK-C4 have been analyzed to test the homogeneity of these materials for the distribution of 14C. The samples were combusted in oxygen under 20 atmospheres pressure using a Parr bomb. The 14C concentrations were determined by liquid scintillation counting using Carbo-Sorb/Permafluor E+ cocktail. The results indicate that these materials are homogeneous with respect to 14C concentration even in sub-sample sizes of 0.25 g of the freeze-dried material. The precision of our 14C measurements, as expressed by the % relative standard deviation, is within 5%. The accuracy has been tested by analyzing replicate samples of the IAEA 14C quality assurance materials, C-3 (cellulose) and C-6 (ANU sucrose) and found to be within 3%. The lower limits of detection are 0.08, 0.05 and 0.02 Bq.g−1 of carbon for 20 ml of liquid scintillation mixture (Carbo-Sorb/Permafluor E+ = ∼0.67) loaded with up to 0.4 g of carbon from the sample and counted for 3 cycles of 60, 180 and 1000 min each, respectively. Our measurements of 14C specific activities of MK-B and MK-C4 are 0.26±0.01 and 15.3±0.4 Bq.g−1 of carbon, respectively.
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