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  • 1990-1994  (2,422)
  • 1900-1904  (1,583)
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  • 1
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Accelerators, capable of producing beams of ions up to several MeV are frequently used for (micro-)analytical purposes. In the majority of cases, the activities are centered around an accelerator previously exclusively used for studies in nuclear physics; but recently, at a number of laboratories completely dedicated “analytical” accelerators have been installed. In this paper an overview is given of the analytical possibilities opened up with the availability of these ion beams.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The aroma of wine consists of 600 to 800 aroma compounds from which especially those, typical for the variety, are already present in the grapes. The aroma extracts — received by extraction with trichlorofluoromethane — are separated by gas chromatography. There are significant varietal differences between the aromagrams (“fingerprint pattern”). Thus the amount of some flavour compounds (“key substances”) shows typical dependence on the variety. Especially monoterpene compounds play an important role in the differentiation of wine varieties. The German white wines can be differentiated into three groups only by quantitative determination of 12 monoterpenes (“terpene profile”). These groups are: “Riesling type”, “Muscat type” and “Silvaner-Weißburgunder type”. Such “terpene profiles” are also useful for the separation of real Riesling wines from others called Riesling (e.g. Welschriesling, Kap Riesling, Emerald Riesling) but not produced from grapes of the variety Riesling. Including further components and by means of statistical methods as for example linear discriminant analysis even the different varieties within the mentioned groups (for instance the “Riesling”-group: Riesling, Kerner, Ehrenfelser, Bacchus, Müller-Thurgau) can be separated from each other. To identify compounds causing “off-flavours” the sniffing technique is the method of choice. The off-flavour is pinpointed during gas chromatography separation of the complex aroma mixture by effluent sniffing. Once allocated, the chemical nature of the off-flavours is elucidated by spectroscopic methods. Substances contributing to the green pepper taint, the strawberry note, mousiness, corkiness etc. in wine could be found in this way.
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A survey of procedures for analytical quality control with emphasis on the use of certified reference materials is given. Requirements for the use and for the preparation of reference materials are presented.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Analysts should consider more than simply the determination of the composition of the test portion provided; they should also assess the degree to which the test portion represents the population under evaluation. To do this requires an understanding of both sampling theory and of practical sampling strategies. An acceptable sampling program should include an adequate statistical design, proper sample collection and transport to the analytical laboratory, and proper training of those performing the sampling. Statistical theories and relations that can serve as aids for more efficient sampling include those of Ingamells and Switzer, Gy, Benedetti-Pichler, and others; most of these apply to particulate mixtures and are based on Gaussian distributions. Other treatments of sampling include geostatistical procedures such as kreiging, and the use of fractals. Many environmental and industrial monitoring and quality control operations now in use are based on sampling protocols arrived at by ad hoc procedures. The quality of trace analytical data can be improved and costs of analyses decreased by developing better sampling plans.
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  • 5
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A review is given on different techniques in laser spectroscopy of atoms and molecules, which allow high spectral resolution and a very high detection sensitivity of small samples. Analytical applications of the techniques are discussed for basic scientific research, as well as for environmental problems and technical processes. Possible trends of laser spectroscopy, in particular with respect to applications in biology and medicine are shortly outlined.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Photothermal spectroscopy relies on the detection of thermal or acoustic waves generated by the absorption of optical radiation and subsequent radiationless deexcitation. With this technique the absorbed energy is detected directly. Hence, weakly absorbing, opaque and scattering samples can be readily addressed with this spectroscopy. Various photothermal and photoacoustic detection schemes and the underlying physical principles are discussed. The potential and the limitations of this technique are highlighted with typical analytical applications.
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Laser microprobe mass spectrometry (LMMS) employs a highly focused UV laser beam to ionise a microvolume in the order of 1 μm3. The produced ions are then mass-separated in a time-of-flight (TOF) or a Fourier Transform (FT) mass spectrometer. The technique allows element localisation, detailed speciation of inorganic substances and structural information of organic molecules. Inorganic applications are treated in the preceding part. This paper will focus on the organic aspects. Selected examples illustrate that TOF LMMS can achieve structural characterisation of molecules, untractable by conventional mass spectrometric techniques. Applicability to the analysis with high spatial resolution is shown and the need for surface availability of organic target molecules is discussed. The recently developed FT LMMS may fulfil the need for better mass resolution. However, the comparability of FT LMMS results with TOF LMMS data is not yet obvious.
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  • 8
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A systematic survey will be given on different strategies of calibration in dependence on given analytical and statistical conditions, particularly on several procedures of least squares regression (ordinary, orthogonal, unweighted and weighted LSR), of robust regression, addition methods and multicomponent calibration. In this connection calibration by means of latent variables (principal component regression PCR, partial least squares PLS) will be dealt with. The special conditions in the case of microanalysis and surface analysis will be considered under practical analytical as well as chemometrical aspects. Problems of homogeneity, representativness of samples and sample regions will be treated.
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  • 9
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The high activity of the radionuclides 65Ni (t1/2=2.52 h) and 58Co (t1/2=70.8 d) imposes severe limitations on the performance of direct instrumental neutron activation analysis of nickel. The extent of the interference of the 58Co depends on the ratio of the fluxes of the fast and thermal neutrons. A method of selective removal of cobalt, based on extraction with β-nitroso-α-naphthol has been developed for the purpose of radiochemical NAA. Separation yields have been determined for 36 elements. The detection limits obtainable with both the instrumental and the radiochemical method are 〈10−4 μg/g for the elements Au, Eu, Ir, La, Sc and Sm, between 10−4 and 10−3 μg/g for Cr, Cs, Hf, Hg, Lu, Re, Sb, Ta, Th, Tm and Yb, between 10−3 and 10−2 μg/g for As, Ag, Br, Ce, Ga, Na, Ru, Se, W and Zn, and in the range 0.01–1 μg/g for Ba, Cd, Co, Fe, In, K, Mo, Nd, Pd, Rb, Sn, U and Zr.
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  • 10
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The suitability of laser Raman spectrometry in process control is demonstrated by comparing results obtained under standard measuring conditions and with special optical fibers. The applicability of capillary tubes which can improve sensitivity in remote sensing is investigated and possible distortions of Raman spectra sampled with optical fibers are described. In preliminary experiments with U(VI) solutions it could be shown that internal standardization using the 1650 cm−1 water band is possible in the process control of aqueous solutions.
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