ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1995-1999  (38)
  • 1950-1954  (27)
Collection
Years
Year
  • 1
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Whole rock and mineral stable isotope and microprobe analyses are presented from granitoids of the North Chilean Precordillera. The Cretaceous to Tertiary plutonic rocks contain important ore deposits and frequently display compositional and textural evidence of hydrothermal alteration even in barren rocks. Deuteric alteration includes replacement of biotite and amphibole by chlorite and epidote, sericitization and saussuritization of feldspars, and uralitization of clinopyroxene and/or amphibole. While whole rock compositions are not significantly affected, compositional variations in amphiboles suggest two types of hydrothermal alteration. Hornblende with actinolitic patches and rims and tight compositional trends from hornblende to Mg-rich actinolite indicate increasing oxygen fugacity from magmatic to hydrothermal conditions. Uralitic amphiboles exhibiting irregular Mg-Fe distribution and variable Al content are interpreted as reflecting subsolidus hydration reactions at low temperatures. The δD values of hydrous silicates vary from −63 to −105‰. Most δ18O values of whole rocks are in the range of 5.7 to 7.7‰ and are considered normal for igneous rocks in the Andes. These δ18O values also coincide well with the oxygen isotope composition of geochemically similar recent volcanics from the Central Andean Volcanic Zone (δ18O = 7.0–7.4‰). Only one sample in this study (δ18O = 3.0‰) appears to be depleted by isotope exchange with light meteoric water at high temperatures. The formation of secondary minerals in all other intrusions is mainly the product of deuteric alteration. This also holds true for the sample from El Abra, the only pluton associated with mineralization. This indicates the dominant role of a magmatic rather than a meteoric fluid in the alteration of the Cretaceous and Tertiary granitoids in northern Chile.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  An isotope dilution mass spectrometric (IDMS) method, using the formation of positive thermal ions, was developed for Cr(III) and Cr(VI) speciation in aerosol particles. Cr(III) and Cr(VI) spike species, enriched in 53Cr, were applied for the isotope dilution step. After leaching of filter collected aerosol samples by an alkaline solution at pH 13, species separation was carried out by extraction with a liquid anion exchanger in methyl isobutyl ketone. Cr(VI) in the organic phase was re-extracted into an ammoniacal solution and chromium was then isolated from both fractions of species by electrodeposition. Detection limits of 30 pg/m3 for Cr(III) and of 8 pg/m3 for Cr(VI) were achieved in atmospheric aerosols for volumes of air samples of about 120 m3. These low detection limits allowed the determination of chromium species in continental aerosol particles in dependence on different seasons. The Cr(III) /Cr(VI) ratio was always found to be about 0.3 whereas dust from soil erosion, which is probably the primary source of chromium in the atmosphere, showed higher ratios. This indicates that chromium is oxidized in the atmosphere. The accuracy of the method was demonstrated in two interlaboratory comparisons of Cr(VI) determinations in welding dust samples. The IDMS method also contributed to the certification of a corresponding standard reference material organized by the Standard Reference Bureau of the European Union. Chromium speciation, including the determination of elemental chromium Cr(0), was carried out in aerosols of different welding processes for stainless steel. These analyses showed distinct differences in the distribution of chromium species in the welding process and can be used as an exact calibration method for routine methods in this important field of monitoring corresponding working places.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Isotope-labelling exchange experiments were carried out to investigate the kinetic stability of Cr(III) complexes with humic substances (HS). To compare the results with those of an ion, not expected to form kinetically stable HS complexes with respect to its electron configuration, Cu(II) was investigated under the same conditions. HS solutions of different origin were therefore spiked with 53Cr(III) or 65Cu(II) after saturation of HS with chromium and copper of natural isotopic composition. In fractions of metal/HS complexes with different molecular weight, obtained by ultrafiltration and HPLC/ICP-MS using size exclusion chromatography (SEC), respectively, the isotope ratios of chromium and copper were determined by ICP and thermal ionisation mass spectrometry. Distinct differences in the isotopic composition of chromium were found in the permeate of the ultrafiltration compared with the corresponding unseparated solution, which indicates kinetically stable Cr(III)/HS complexes. On the other hand, the copper isotopic composition was identical in the permeate and the unseparated solution, which shows that a total exchange of Cu2+ ions took place between free and HS complexed copper ions. The SEC/ ICP-MS experiments also resulted in a different isotopic distribution of chromium in the chromatographically separated complexes whereas the copper complexes, separated by SEC, showed identical isotopic composition. The kinetic stability of Cr(III)/HS complexes could be explained by the d3 electron configuration of Cr3+ ions, a fact which is well known from classical Cr(III) complexes, and influences substantially the mobility of this heavy metal in the environment.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A mass spectrometric method for the determination of chlorine, bromine and iodine species of humic substances (HS) has been developed by coupling a HPLC system with ICP-MS. Using size exclusion chromatography, the method was applied to the characterization of natural water samples (ground water, seepage water from soil, brown water) and a sewage water sample. Quantification of iodine/HS species was carried out by the on-line isotope dilution technique, which was not possible for bromine and chlorine species because of mass spectroscopic interferences by using a quadrupole ICP-MS. Characteristic fingerprints of the halogen/HS species, correlated with the corresponding UV chromatogram, were obtained dependent on the different origin of HS. Biological influences were indicated when following changes of the iodine/HS species composition by aging. The formation of iodine/HS species from inorganic iodide was investigated by labelling experiments with an 129I– spike solution, resulting in the finding that specific HS fractions are preferably iodinated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An isotope dilution mass spectrometric (IDMS) method has been developed for the simultaneous determination of the complexes of 11 heavy metals (Ag, Cd, Cu, Mo, Ni, Pb, Tl, U, W, Zn and Zr) with humic substances (HS) by coupling HPLC with ICP-MS and applying the on-line isotope dilution technique. The HPLC separation was carried out with size exclusion chromatography. This HPLC/ICP-IDMS method was applied to samples from a brown water, ground water, sewage and seepage water as well as for a sample containing isolated fulvic acids. The total contents of heavy metals and of their complexes were analyzed in these samples with detection limits in the range of 5–110 ng/L. The analysis of heavy metal/HS complexes from the different waters resulted in characteristic fingerprints of the distribution pattern of heavy metals in the separated HS fractions. A comparison between the total heavy metal concentrations and their portions bound to humic substances showed distinct differences for the various metals. Simultaneous 12C detection was used for the characterization of HS complexes not identified by UV detection and for the determination of relative DOC concentrations of chromatographic peaks.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-1211
    Keywords: Key words Lipopolysaccharide binding protein ; Chromosome mapping ; Mouse ; Transcription ; Microsatellite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique, which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore fit the recommendations of the European Union (detection limit〈2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace bromide and bromate species in water samples.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  During the cruise ANT X/1 and 2 of the research vessel Polarstern from November 1991 to March 1992, 39 surface water samples of the Atlantic Ocean from 42°N to 72.5°S were collected and analysed for their concentration of volatile iodinated and brominated hydrocarbons. The concentration of chlorophyll-a was used as an indicator for phytoplankton, which is one of the main producers of iodinated and brominated compounds in the ocean. For determination of chlorophyll-a, fluorescence spectroscopy was applied, whereas the measurement of halogenated volatile hydrocarbons was carried out by a purge and trap system with subsequent gas chromatographic separation and detection by an electron capture detector. With this technique the brominated substances CHBr3, CH2Br2, CHBr2Cl and CHBrCl2 have been detected in the range of 〈0.03 ng/L to 15 ng/L. For these volatile bromomethanes a distinct concentration profile was found. CHBr3 was always found to be the substance with the highest concentration followed by CH2Br2, CHBr2Cl and CHBrCl2. It could also be shown that in addition to CH3I, which for a long time was believed to be the only volatile iodinated substance in the marine environment, other iodinated substances like CH2ClI, CH2I2 and CH3CH2CH2I exist in the range of 〈0.01 ng/L to 2.2 ng/L in surface water of the Atlantic Ocean. Although it is improbable that chlorophyll-a is directly involved in the marine production of halogenated hydrocarbons, it was found that it could be used as an indicator for the biogenic formation of brominated compounds, whereas the correlation between chlorophyll-a and the iodinated substances was not of the same quality. The positive correlation between bromoform and dibromomethane proves the same biogenic origin and mechanism of formation, which could not be found for the different iodinated compounds.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Precise boron isotope ratio measurements with negative thermal ionization mass spectrometry were used for the identification of ground water contaminations by leakages of landfills. BO- 2thermal ions were produced to determine the 11B/10B isotope ratio, which was expressed as δ11B value in ‰ normalized to the standard reference material NIST SRM 951. For example, household waste influences the boron isotope ratio by specific components such as washing powder. In the case of one investigated landfill low δ11B values correlate well with high boron concentrations in contaminated seepage water samples and vice versa for uncontaminated ground water samples. Possible boron contributions of rainwater were taken into account, determining a boron content of 2.3 μg/L and a δ11B value of 13.1‰ for a representative sample. Such low boron concentrations were determined by isotope dilution mass spectrometry (detection limit 0.3 μg/L) whereas higher contents were also analyzed by a spectrophotometric method. However, different sources of contamination could only be identified by the isotope ratio and not by the concentration of boron.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...