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  • 1995-1999  (1,011)
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  • 11
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Substance abuse is a major problem worldwide. There is considerable emphasis placed upon testing individuals for evidence of use of controlled substances. Because the consequences of a positive test can be quite severe, laboratories conducting such tests must rigorously follow a carefully designed quality assurance program. Such a QA program should include use of reference materials to assure that the methods used to detect and quantify drugs are providing accurate results. The National Institute of Standards and Technology (NIST) supports accuracy in drugs of abuse testing by providing Standard Reference Materials (SRMs) with certified concentrations of drugs of abuse in urine- and hair-based reference materials. NIST, working in collaboration with the College of American Pathologists (CAP), has developed urine-based SRMs for marijuana metabolite, cocaine metabolite, morphine and codeine, and morphine glucuronide and CAP Reference Materials for amphetamines and phencyclidine. Certification measurements performed at NIST involve two independent methods for each analyte, one of which always uses GC/MS with the other usually being an LC method with either MS or UV detection. Work has recently been completed on a seven component drug in urine SRM. In addition NIST conducts research in the analysis of hair for drugs of abuse. To assist laboratories testing hair for that purpose, NIST has developed two drugs in hair reference materials.
    Type of Medium: Electronic Resource
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  • 12
    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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  • 13
    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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  • 14
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Recently the subcommittee on Food Definition of the AOAC INTERNATIONAL Task Force on Methods for Nutrition Labeling proposed a “Food Matrix Organizational System” [4] to systematically judge the applicability of collaboratively studied methods over a range of food matrices. This system describes a food matrix by its location in one of nine sectors in a triangle, with each point of the triangle defined as representing 100% and the opposite side representing 0% of the normalized contents of each of three major components of FAT, PROTEIN and CARBOHYDRATE. Foods falling within the same sector would be chemically similar and thus should behave in a similar analytical manner. This same scheme can be used to select one or two food matrices representing each sector, for development of a series of reference materials representing all foods. The list of 5250 foods contained in the USDA Nutrient Data Base for Standard Reference has been sorted and matched to this schematic to determine the scope of the selection process. In addition the list of foods in the “USDA Data Base for Food Consumption Surveys” has been examined. Results and progress of this selection process are reported.
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  • 15
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A PC-based interactive programme is described which is designed to help in suggesting the best estimate of the true value of an analyte content from results of collective studies aiming at deriving consensus values and/or reference material preparation by employing combined statistical and analytical considerations. The Grubbs, Dixon, Huber tests, and the coefficients of skewness and curtosis tests are used for outlier detection, the Bartlett, Cochran, and the standard error tests are employed for testing variance homogeneity testing and/or variance outliers identification, while the normality of results distribution is tested according to the Kolmogoroff-Smirnoff-Lilliefors and Shapiro-Wilk tests. One-way analysis of variance (ANOVA) is employed to test differences among means of results obtained in different conditions (laboratories, analytical methods, etc.) and to calculate the overall mean and its confidence interval accordingly. Points for an analytical discussion are given which should be considered prior to a decision whether a result of a trace element determination, identified as an outlier from statistical reasons, should be rejected.
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  • 16
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two batches of a reference material “Creatinine in Human Urine” have been prepared with creatinine concentrations at the physiological level, and used in interlaboratory comparisons in which up to 26 laboratories participated employing up to 4 independent methods. The 95% confidence intervals obtained for the certified creatinine concentrations are better than the “acceptable ranges” of commercially control samples available for clinical laboratories, the certified values being traceable to mean values of the commercial control samples. Thus, a suitable reference material has been prepared for the quality assurance of environmental and occupational health studies in which the concentration of a pollutant or its metabolites in human urine has to be related to the creatinine concentration.
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  • 17
    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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  • 18
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract As part of the analytical assurance system of the FAO European Cooperative Research Network on Trace Elements programme an ARC/CL-coded carrot flakes powder (CFP) candidate reference material (RM) has been prepared from a lot of commercial carrot flakes. The candidate RM has been homogenized using a Robot Coupe blender fitted with titanium blades, carefully homogenized in large teflon/polypropylene containers, bottled in 1000 numbered polyethylene containers (20 g samples) and tested for homogeneity. Interlaboratory comparison studies for 9 essential elements, cadmium and total dietary fiber (TDF) based on the AOAC-method resulted in the characterization of the contents of those compounds in the above material. After exclusion of outliers, mean values from at least nine different laboratories based altogether on three independent analytical principles have been used to calculate the recommended concentration ranges for mineral elements. Testing of homogeneity and stability for β-carotene over a period of one year has been additionally carried out. The mean water content in the material amounted to 4.97% and remained stable over a one-year period. Homogeneity of the RM was within 3.0% for almost all included mineral elements as tested for a sample size of 0.5 g. The 95% confidence limits for the mean values of the established recommended concentrations of mineral elements in the present ARC/CL Carrot Powder candidate RM fell within 5% for all the other elements and TDF except for Fe (6.3%) and B (5.7%). The stability of β-carotene in the present candidate RM stored in darkness over a one-year period at room temperature was within 6.3%.
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  • 19
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Selection criteria for production of food reference materials need to simultaneously consider realistic proximate matrix compositions, emerging trends for the nutritional and toxicological effects of less-emphasized trace elements (e.g., B, Li, Si, and V), chemical speciation (especially for As, Hg, Se, and Sn), and analyte certification requirements from the analyst's point of view. For the most part, currently available Certified Reference Materials (CRMs) do not meet many of these needs. Candidate CRMs with relevant concentrations of trace elements could be chosen from similar foods with different proximate compositions (e.g., fat content of milk products, meat, or soya flour). Explicit guidance must accompany CRMs so that variations in measured trace element concentrations arising from procedural lapses and basis weight are avoided.
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  • 20
    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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