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  • Column liquid chromatography  (349)
  • Nitrogen fixation  (142)
  • Textbook of geodesy
  • Springer  (495)
  • Irkutsk : Ross. Akad. Nauk, Sibirskoe Otd., Inst. Zemnoj Kory
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • 2005-2009  (3)
  • 1985-1989  (492)
Collection
Keywords
Publisher
  • Springer  (495)
  • Irkutsk : Ross. Akad. Nauk, Sibirskoe Otd., Inst. Zemnoj Kory
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • Wiley-Blackwell  (3)
  • de Gruyter  (2)
Years
Year
  • 1
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    Iceland Geodynamics - Crustal Deformation and Divergent Plate Tectonics (2006)
    Springer
    In:  Corporate, Florida, Springer, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (3-540-24165-5, XXVI + 228 p.)
    Details
    Publication Date: 2006
    Description: This book provides a summary of geodynamic results from Iceland that presently are found in a great number of scientific articles, but have not been collected before in a book
    Keywords: Textbook of geodesy ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Geodesy ; Plate tectonics ; GeodesyY
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Volcano Deformation - New Geodetic Monitoring Techniques (2006)
    Springer
    In:  Cambridge, Springer, vol. LXXVIII, no. 2, pp. 125-169, (ISBN: 3-540-42642-6, Approx. 620 p. 30 illus., Hardcover)
    Details
    Publication Date: 2006
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Volcanology ; Geodesy ; Global Positioning System ; InSAR ; Textbook of geodesy
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Physical Geodesy (2005)
    Springer
    In:  New York, 390 pp., Springer, vol. 36, no. XVI:, pp. 1-14, (ISBN 3-211-23584-1)
    Details
    Publication Date: 2005
    Description: Motivation, Fundamentals of potential theory The gravity field of the earth, Gravity reduction, Heights The geometry of the earth, Gravity field outside the earth, Space methods Modern views on the determination of the figure of the earth Statistical methods in physical geodesy, Least-squares collocation Computational methods, References, Subject index
    Keywords: Textbook of geodesy ; Global Positioning System ; Geoid ; Gravimetry ; Potential ; Theory ; Reference ; Systems ; collocation ; geodetic ; satellite ; techniques ; heights
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
    Electronic Resource
    Electronic Resource
    Location of two isoenzymes of NADH-dependent glutamate synthase in root nodules of Phaseolus vulgaris L. (1989)
    Springer
    Planta 179 (1989), S. 441-447 
    Details
    ISSN: 1432-2048
    Keywords: Glutamate synthase ; Glutamine synthetase ; Nitrogen fixation ; Phaseolus (glutamate synthase) ; Plastid (glutamate synthase) ; Root nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The two isoenzymes of NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14), previously identified in root nodules of Phaseolus vulgaris L., have both been shown to be located in root-nodule plastids. The nodule specific NADH-GOGAT II accounts for the majority of the activity in root nodules, and is present almost exclusively in the central tissue of the nodule. However about 20% of NADH-GOGAT I activity is present in the nodule cortex, at about the same specific activity as this isoenzyme is found in the central tissue. Glutamine synthetase (GS; EC 6.3.1.2) occurs predominantly as the γ polypeptide in the central tissue, whereas in the cortex, the enzyme is represented mainly by the β polypeptide. Over 90% of both GS and NADH-GOGAT activities are located in the central tissue of the nodule and GS activity exceeds NADH-GOGAT activity by about twofold in this region. Using the above information, a model for the subcellular location and stoichiometry of nitrogen metabolism in the central tissue of P. vulgaris root nodules is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397583
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  • 5
    Electronic Resource
    Electronic Resource
    Nitrogen fixation in the lichen Lobaria pulmonaria in elevated atmospheric carbon dioxide (1989)
    Springer
    Oecologia 79 (1989), S. 566-568 
    Details
    ISSN: 1432-1939
    Keywords: Carbon dioxide ; Lichen ; Lobaria ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thalli of Lobaria pulmonaria (L.) Hoffm., a nitrogen-fixing epiphyte common in mesic temperate forests, were collected in a Douglas-fir (Pseudotsuga menziesii Franco) forest near Corvallis, Oregon, and maintained for 20 to 40 days in controlled-environment chambers with atmospheric CO2 concentrations of 374 and 700 μll-1. Nitrogenase activity, which was assayed by the acetylene reduction method, was approximately doubled in the lichen maintained in elevated CO2. Increases in nitrogen fixation by lichens may be an important part of the integrated ecosystem response to rising CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378677
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  • 6
    Electronic Resource
    Electronic Resource
    Energy transduction efficiencies in nitrogenous oxide respirations of Azospirillum brasilense Sp7 (1989)
    Springer
    Archives of microbiology 151 (1989), S. 445-453 
    Details
    ISSN: 1432-072X
    Keywords: Denitrification ; Growth yield measurements ; Nitrate respiration ; Nitrogen fixation ; Proton translocations in respirations ; Azospirillum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For Azospirillum brasilense Sp7, the energy transformation efficiencies were measured in anaerobic respirations with either nitrate, nitrite or nitrous oxide as respiratory electron acceptors by determining the maximal molar growth yields and the H+-translocations using the oxidant pulse method. In continuous cultures grown with malate limiting, the maximal molar growth yields (Y s max -values) were essentially the same with O2 or N2O but were 1/3 and 2/3 lower with NO 2 - or NO 3 - , respectively, as respiratory electron acceptors. Both the maximal molar growth yields and the maintenance energy coefficients were surprisingly high when Azospirillum was grown with nitrite as the sole electron acceptor and source for N-assimilation. Growth under N2-fixing conditions drastically reduced the Y s max -values in the N2O and O2-respiring cells. In the H+-translocation measurements, the $$\vec H^ + $$ /oxidant ratios were 5.6 for O2→H2O, 2.5–2.8 for NO 3 - →NO 2 - , 2.2 for NO 2 - →N2O and 3.1 for N2O→N2 respirations when the cells were preincubated with valinomycin and K+. All the values were enhanced when the experiments were performed with valinomycin plus methyltriphenylphosphonium (=TPMP+) cation. The uncoupler carbonyl cyanide-m-chlorophenyl-hydrazone diminished the H+-excretion indicating that this translocation was due to vectorial flow across the membrane. In the absence of any ionophore, nitrate and nitrite respirations were accompanied by a H+-uptake $$(NO_3^ - \to N_2 = - 2.9 \vec H^ + /NO_3^ - and NO_2^ - \to N_2 = - 2.5 \vec H^ + /NO_2^ - )$$ . Any significant H+-translocation could not be detected in N2O- and O2-respirations under these conditions. It is concluded that nitrate reduction proceeds inside the cytoplasmic membrane, whereas nitrite is reduced extramembraneously. The data are not conclusive for the location of nitrous oxide reductase. The maximal molar growth yield determinations and the absence of any H+-uptake in untreated cells indicate a cytoplasmic orientation of the enzyme similar to the terminal cytochrome oxidase of respiration. The low H+-extrusion values for N2O-respiration compared to O2-respiration in cells treated with valinomycin plus TPMP+ are, however, not in accord with such an interpretation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00416605
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  • 7
    Electronic Resource
    Electronic Resource
    Cloning of a DNA region from Bradyrhizobium japonicum encoding pleiotropic functions in heme metabolism and respiration (1989)
    Springer
    Archives of microbiology 151 (1989), S. 203-212 
    Details
    ISSN: 1432-072X
    Keywords: Bradyrhizobium ; Gene cloning ; Heme ; Marker exchange mutagenesis ; Nitrogen fixation ; Respiration ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Random and site-directed Tn5-induced mutagenesis of Bradyrhizobium japonicum yielded two mutations, one in strain 2960 and the other in strain 2606::Tn5-20, which mapped close to each other but in separate genes. The corresponding wild-type genes were cloned, and their approximate location on the cloned DNA was determined. Mutant 2960 was Fix- and formed green nodules on soybean, whereas strain 2606::Tn5-20 had ca. 4% of wild-type Fix activity and formed white nodules. Cytochrome oxidase assays (Nadi tests) showed a negative reaction with both mutants, indicating a functional deficiency of cytochrome c or its terminal oxidase or both. However, the mutants grew well under aerobic conditions on minimal media with different carbon sources. Furthermore, mutant 2960 had a reduced activity in hydrogen uptake, was unable to grow anaerobically with nitrate as the terminal electron acceptor and 2960-infected soybean nodules contained little, if any, functional leghemoglobin. Southern blot analysis showed that a B. japonicum heme biosynthesis mutant [strain LO505: O'Brian MR, Kirshbom PM, Maier RJ (1987) Proc Natl Acad Sci USA 84: 8390–8393] had its mutation close to the Tn5 insertion site of our mutant 2606::Tn5-20. This finding, combined with the observed phenotypes, suggested that the genes affected in mutants 2960 and 2606::Tn5-20 were involved in some steps of heme biosynthesis thus explaining the pleiotropic respiratory deficiencies of the mutants. Similar to strain LO505, the mutant 2606::Tn5-20 (but not 2960) was defective in the activity of protoporphyrinogen IX oxidase which catalyzes the penultimate step in the heme biosynthesis pathway. This suggests that one of the two cloned genes may code for this enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00413131
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  • 8
    Electronic Resource
    Electronic Resource
    Deletion analysis of the nitrogen fixation regulatory gene, nifL of Klebsiella pneumoniae (1989)
    Springer
    Archives of microbiology 151 (1989), S. 180-182 
    Details
    ISSN: 1432-072X
    Keywords: Klebsiella pneumoniae ; Nitrogen fixation ; nifL ; Regulation ; Oxygen control ; Nitrogen control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A number of in-frame deletions have been constructed in the Klebsiella pneumoniae regulatory gene nifL. The effects of each nifL mutation on NifA-mediated expression from the nifH promoter of K. pneumoniae have then been assessed with respect to both nitrogen and oxygen control. These experiments indicate that, in contrast to the situation with the homologous regulatory proteins NtrB and NtrC, NifA activity is not impaired in the absence of NifL. We conclude that the only function of NifL is to inactivate NifA in response to an increase in the nitrogen or oxygen status of the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414436
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  • 9
    Electronic Resource
    Electronic Resource
    Induced genetic variability in Rhizobium leguminosarum for nitrogen fixation parameters in Vicia faba L. (1989)
    Springer
    Theoretical and applied genetics 78 (1989), S. 433-435 
    Details
    ISSN: 1432-2242
    Keywords: Rhizobium ; Irradiation ; Nitrogen fixation ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Sumary The objective of this work was to know the behaviour and variability of Rhizobium leguminosarum after irradiation. The induced variation was tested under greenhouse conditions on the variety JV 3 of broad beans (Vicia faba) in six replications. Induced genetic variabilty was observed for strain, parent and mutant versus parent. Out of 24 irradiated strains, strain 93-32 performed better with a greater number of nodules and higher dry weight of nodules per plant and biological yield. Environment played an important role in the expression of characters observed. High heritability and genetic advance of these traits indicated that the nitrogen fixation ability of Rhizobium can easily be improved by selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265308
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  • 10
    Electronic Resource
    Electronic Resource
    Impact of nodule damage by Rivellia angulata on N2-fixation, growth, and yield of pigeonpea (Cajanus cajan L. Millsp.) grown in a Vertisol (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 95-100 
    Details
    ISSN: 1432-0789
    Keywords: Nodule damage ; Rivellia angulata ; Nitrogen fixation ; Cajanus cajan ; Pigeonpea ; Vertisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Damage caused by Rivellia angulata larvae to pigeonpea root nodules at the ICRISAT center in India was greater in the crop grown on Vertisols (up to 86%) compared to that on Alfisols (20%). Attempts to quantify the field effects of nodule damage on growth and yield of pigeonpea in a Vertisol, involving many heavy applications of soil insecticides (aldrin and hexachlorocyclohexane) failed because the insecticides did not control the pest and adversely affected the growth of the pigeonpea and the subsequent crop of sorghum (Sorgorum bicolor L. Moench). The impact of nodule damage on pigeonpea growth, yield and nutrient uptake was successfully studied in greenhouse-grown plants at three N levels. In this pot study, artificial inoculation with Rivellia sp. led to substantial nodule damage (70%). The results of this damage were a significant overall reduction in nodule dry weight (46%), acetylene reduction activity (31%), total leaf area (36%), chlorophyll content of leaves (39%) and shoot dry weight (23%) 68 days after sowing. At maturity, Rivellia sp. infestation caused significant reductions in top dry weight (22%), root and nodule dry weight (27%), seed dry weight (14%), and total N (29%) and P uptake (19%). The problems and prospects of manipulating nodule damage so as to reduce N losses in pigeonpea are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292565
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  • 11
    Electronic Resource
    Electronic Resource
    Variation in nitrogen fixation among populations ofFrankia sp. andCeanothus sp. in actinorhizal association (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 269-274 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen fixation ; Frankia-Ceanothus spp. association ; Acetylene reduction assay (ARA) ; Microsymbiont population ; Nodules ; Actinomycetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Wildland shrub improvement is needed for sound range and disturbed land revegetation practice. The possibility of selecting superior N2-fixingFrankia-Ceanothus spp. actinorhizal associations was examined. Greenhouse tests were used to expose various soil-borne microsymbiont andCeanothus sp. population accessions in reciprocal combination. The acetylene reduction rate was used as a measure of N2-fixation capacity. There was no significant interaction between host and microsymbiont regardless of source for all variables measured. The acetylene reduction rate, nodule number and mass, plant biomass, and root: shoot ratio were significantly different among soil sources. The acetylene reduction rate was not significantly different amongCeanothus sp. accessions. Neither was it strongly correlated with other variables. It was concluded that the N2-fixation rate is more a function ofFrankia sp. than the hostCeanothus sp. in actinorhizal associations. It appears possible to select soil sources with superior N2-fixing microsymbiont populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00709660
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  • 12
    Electronic Resource
    Electronic Resource
    Azospirillum — plant root associations: A review (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 356-368 
    Details
    ISSN: 1432-0789
    Keywords: Plant-root associations ; Azospirillum spp ; Rhizosphere ; Nitrogen fixation ; Acetylene reduction assay (ARA) ; Phytohormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bacteria of the genus Azospirillum are extensively studied for their plant-growth promoting effect following inoculation. Physiological and biochemical studies of these diazotrophic bacteria are now benefiting from recent breakthroughs in the development of genetic tools for Azospirilum. Moreover, the identification and cloning of Azospirillum genes involved in N2 fixation, plant interaction, and phytohormone production have given new life to many research projects on Azospirillum. The finding that Azospirillum genes can complement specific mutations in other intensively studied rhizosphere bacteria like Rhizobia will certainly trigger the exploration of new areas in rhizosphere biology. Therefore a review of the Azospirillum-plant interactions is particularly timely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263169
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  • 13
    Electronic Resource
    Electronic Resource
    Rice yields as influenced by Azolla N2 fixation and urea N-fertilization (1989)
    Springer
    Plant and soil 114 (1989), S. 63-68 
    Details
    ISSN: 1573-5036
    Keywords: Azolla pinnata ; Nitrogen fixation ; N yield ; Oryza sativa ; Urea-N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Application of 0, 30, 60, 90 and 120 kg N ha−1 of urea (U) in split doses with (and without)Azolla pinnata, R. Brown was studied for three consecutive seasons under planted field condition. Fresh weight (FW), acetylene reduction activity (ARA) and N yield of Azolla were found to be maximum 14 days after inoculation (DAI). Among the different treatments, maximum Azolla growth was recorded in no N control. The FW, ARA and N yield of Azolla were inhibited increasingly with the increase in N levels. Irrespective of season, FW and N yield of Azolla were inhibited only a small extent with 90 kg N ha−1 U, beyond which the inhibition was pronounced. ARA was inhibited only slightly up to 60 kg N ha−1 of U. Grain yield and crop N uptake of rice increased significantly up to 90 kg N ha−1 of U (alone or in combination with Azolla) in the dry seasons (variety IR 36) and up to 60 kg N ha−1 U in the wet season (variety CR 1018).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02203082
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  • 14
    Electronic Resource
    Electronic Resource
    DNA sequence and genetic analysis of the Rhodobacter capsulatus nifENX gene region: Homology between NifX and NifB suggests involvement of NifX in processing of the iron-molybdenum cofactor (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 353-363 
    Details
    ISSN: 1617-4623
    Keywords: Rhodobacter capsulatus ; Nitrogen fixation ; DNA sequence analysis ; nifE, nifN, nifX genes ; Protein comparisons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rhodobacter capsulatus genes homologous to Klebsiella pneumoniae nifE, nifN and nifX were identified by DNA sequence analysis of a 4282 bp fragment of nif region A. Four open reading frames coding for a 51188 (NifE), a 49459 (NifN), a 17459 (NifX) and a 17472 (ORF4) dalton protein were detected. A typical NifA activated consensus promoter and two imperfect putative NifA binding sites were located in the 377 bp sequence in front of the nifE coding region. Comparison of the deduced amino acid sequences of R. capsulatus NifE and NifN revealed homologies not only to analogous gene products of other organisms but also to the α and β subunits of the nitrogenase iron-molybdenum protein. In addition, the R. capsulatus nifE and nifN proteins shared considerable homology with each other. The map position of nifX downstream of nifEN corresponded in R. capsulatus and K. pneumoniae and the deduced molecular weights of both proteins were nearly identical. Nevertheless, R. capsulatus NifX was more related to the C-terminal end of NifY from K. pneumoniae than to NifX. A small domain of approximately 33 amino acid residues showing the highest degree of homology between NifY and NifX was also present in all nifB proteins analyzed so far. This homology indicated an evolutionary relationship of nifX, nifY and nifB and also suggested that NifX and NifY might play a role in maturation and/or stability of the iron-molybdenum cofactor. The open reading rame (ORF4) downstream of nifX in R. capsulatus is also present in Azotobacter vinelandii but not in K. pneumoniae. Interposon-induced insertion and deletion mutants proved that nifE and nifN were necessary for nitrogen fixation in R. capsulatus. In contrast, no essential role could be demonstrated for nifX and ORF4 whereas at least one gene downstream of ORF4 appeared to be important for nitrogen fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334376
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  • 15
    Electronic Resource
    Electronic Resource
    The DNA sequence of the Rhodobacter capsulatus ntrA, ntrB and ntrC gene analogues required for nitrogen fixation (1989)
    Springer
    Molecular genetics and genomics 215 (1989), S. 507-516 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen fixation ; Regulation ; Rhodobacter capsulatus ; Gene sequences ; Transcription factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have determined the DNA sequence for the genes nifR1, nifR2 and nifR4 in the photosynthetic bacterium Rhodobacter capsulatus. These genes regulate transcription of the nifHDK operon and so limit the expression of nitrogen fixation activity to periods of low environmental concentrations of both oxygen and fixed nitrogen. The sequences of these three genes are similar to components of the ntr regulation system in Escherichia coli and Klebsiella pneumoniae. The two-component regulatory system of ntrB and ntrC in E. coli is represented by nifR2 and nifR1 in R. capsulatus and nifR4 in R. capsulatus is the equivalent of the E. coli ntr-related sigma factor ntrA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427050
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  • 16
    Electronic Resource
    Electronic Resource
    Role of metal ions in negative regulation of nitrogen fixation by the nifL gene product from Klebsiella pneumoniae (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 484-491 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen fixation ; nifL ; Repression ; Metal ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ability of the Klebsiella pneumoniae nifL gene product to antagonise NIFA mediated transcriptional activation from the nifH promoter in vivo was inhibited either by metal deprivation, or by the presence of the iron chelators EDDA or Desferal in the growth medium. This inhibition of the repressive activity of NIFL was reversed by the addition of ferrous or manganous ions to the medium but was unaffected by other transition metals. The dependence on metal ions for NIFL activity was observed when NIFL was overexpressed and when cultures were exposed to oxygen or high levels of fixed nitrogen. Immunochemical evidence suggests that NIFL and NIFA associate to form a functional protein complex. Metal ions are apparently not required for the formation of this complex.
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    URL: http://dx.doi.org/10.1007/BF00334394
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  • 17
    Electronic Resource
    Electronic Resource
    TheKlebsiella pneumoniae PII protein (glnB gene product) is not absolutely required for nitrogen regulation and is not involved in NifL-mediatednif gene regulation (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 474-480 
    Details
    ISSN: 1617-4623
    Keywords: glnB ; Klebsiella pneumoniae ; Nitrogen control ; Glutamine synthetase ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The role of theKlebsiella pneumoniae PII protein (encoded byglnB) in nitrogen regulation has been studied using two classes ofglnB mutants. In Class I mutants PII appears not to be uridylylated in nitrogen-limiting conditions and in Class II mutants PII is not synthesised. The effects of these mutations on expression from nitrogen-regulated promoters indicate that PII is not absolutely required for nitrogen control. Furthermore the uridylylated form of PII(PII-UMP) plays a significant role in the response to changes in nitrogen status by counteracting the effect of PII on NtrB-mediated dephosphorylation of NtrC. PII is not involved in thenif-specific response to changes in nitrogen status mediated by NifL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464920
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  • 18
    Electronic Resource
    Electronic Resource
    TheRhizobium-legume symbiosis Two methods to discriminate between nodules and other root-derived structures (1989)
    Springer
    Protoplasma 149 (1989), S. 82-88 
    Details
    ISSN: 1615-6102
    Keywords: Legumes ; Nitrogen fixation ; Nodulation ; Rhizobium ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two methods have been developed in order to discriminate between lateral roots, nodules and root-derived structures which exhibit both root and nodule histological features and which can develop on legumes inoculated with certainRhizobium mutants. The first method, known as the “clearing method”, allows the observation by light microscopy of cleared undissected root-structures. The second, known as the “slicing method”, is a complementary technique which provides a greater degree of structural information concerning such structures. The two methods have proved invaluable in defining unequivocally the nature of the interaction between a rhizobial strain and a legume host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322980
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  • 19
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    Ultrastructural characteristics of the host-symbiont interface in nitrogen-fixing peanut nodules (1989)
    Springer
    Protoplasma 150 (1989), S. 19-26 
    Details
    ISSN: 1615-6102
    Keywords: Nitrogen fixation ; Peanut ; Root nodules ; Dense body ; Microbody ; Oleosome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrogen-fixing peanut root nodules are characterized by their unique structural organization, distinct from other legume nodules. The focus of this study has been in and around the hostsymbiont interface, where the bacterioid and the host cell surface (peribacteroid membrane envelope) interact during symbiosis. The infected nodule cells have revealed the presence of lipid bodies (oleosomes) in intimate association with the peribacteroid membrane, which encloses the large spherical bacteroids with a relatively narrow peribacteroid space. Electron dense structures, referred to as dense bodies have been found attached to the bacteroid outer membranes at the host-symbiont interface. The dense bodies are osmiophilic, amorphous and 3,3′-diaminobenzidine positive. The isolated intact bacteroids with dense bodies attached to their cell wall showed significant catalase activity. Many microbodies showing DAB-positive reaction have been found in the host cytoplasm, associated closely with the peribacteroid membrane. These ultrastructural and cytochemical characteristics of peanut root nodules suggest that lipids are utilized during symbiosis and the dense bodies and microbodies may be involved in the catabolic process.
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    URL: http://dx.doi.org/10.1007/BF01352917
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  • 20
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    Genes coding for the reversible ADP-ribosylation system of dinitrogenase reductase from Rhodospirillum rubrum (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 340-347 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen fixation ; draT ; draG ; TTG initiation codon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrogen fixation activity in the photosynthetic bacterium Rhodospirillum rubrum is controlled by the reversible ADP-ribosylation of the dinitrogenase reductase component of the nitrogenase enzyme complex. This report describes the cloning and characterization of the genes encoding the ADP-ribosyltransferase (draT) and the ADP-ribosylglycohydrolase (draG) involved in this regulation. These genes are shown to be contiguous on the R. rubrum chromosome and highly linked to the nifHDK genes. Sequence analysis revealed the use of TTG as the initiation codon of the draT gene as well as a potential open reading frame immediately downstream of draG. The mono-ADP-ribosylation system in R. rubrum is the first in which both the target protein and modifying enzymes as well as their structural genes have been isolated, making it the model system of choice for analysis of this post-translational regulatory mechanism.
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    URL: http://dx.doi.org/10.1007/BF00331287
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    Chromatographic analysis of penstemide and serrulatoloside by high-performance liquid chromatography and gradient thin-layer chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 24-26 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Penstemide and serrulatoloside
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Penstemide and serrulatoloside, two iridoids of similar molecular structure, were separated by stepwise gradient TLC in a straight-phase systems (silica-ethyl acetate+isopropanol) and by HPLC in a reversed-phase system (ODS-silica — water+methanol).
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    URL: http://dx.doi.org/10.1007/BF02290399
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    RPLC retention of 1,ω-di(alkoxy)-polysulphides (1989)
    Springer
    Chromatographia 27 (1989), S. 27-30 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 1,ω-Di(alkoxy)-polysulphides ; Retention contributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of S2Cl2 with alcohols yields products, the reversed-phase liquid chromatograms of which are similar to those of dialkyl-polysulphides RSnR, i.e., they represent homologous series. Four of the products were identified via GC-MS as 1,ω-di(alkoxy)-polysulphides having the general structure ROSnOR. Retention contributions of alkyl groups R and sulphur atoms in the −Sn — chain are not much different from values observed with polysulphides. The effect of oxygen, however, is only about −100 index units per O atom, while in dialkyl ethers values of −500 units have been reported.
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    URL: http://dx.doi.org/10.1007/BF02290400
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    The effect of alcoholic mobile phase modifiers on retention and stereoselectivity on a commercially available cellulose-based HPLC chiral stationary phase: An unexpected reversal in enantiometric elution order (1989)
    Springer
    Chromatographia 27 (1989), S. 15-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral recognition process ; Enantiomeric elution order ; Mobile phase modifiers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three enantiomeric solutes, a sulphoxide, a piperidine derivative and a methyl ester have been chromatographed on an HPLC chiral stationary phase (CSP) based upon cellulose-tribenzoate (Chiralcel OB-CSP). The mobile phases used in the study were composed of hexane modified with homologous series of primary, secondary and cyclic alcohols. Interesting reversals in enantiomeric elution order have been observed for 2-phenoxypropanoic acid methyl ester associated with changes in chain length or ring size of the alcohol mobile phase modifier. The results of the study suggest that at least two chiral recognition mechanisms operate on the OB-CSP and point out the importance of acquiring elution order data in all studies involving chiral stationary phases.
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    URL: http://dx.doi.org/10.1007/BF02290397
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    Separation of bromo- and iodosubstituted thyronines by high-performance liquid chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 101-104 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bromo/iodosubstituted thyronines ; Mobile phase optimization ; Radioimmunoassay detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high performance liquid chromatographic method on C-18 bonded silica is described for the separation of trisubstituted iodo/bromothyronines, which exert thyroid hormone activity. The composition of the mobile phase has been systematically optimized resulting in a ternary mixture of methanol/acetonitrile/water acidified with trifluoroacetic acid. The applicability of ultraviolet absorption detection, amperometric detection and off-line radioimmunoassay was investigated. The latter method allows detection of the different iodo/bromothyronines down to 40–120 ng/l mobile phase; this sensitivity is high enough for application to thyroid hydrolysates in order to clarify the question as to whether bromine can substitute iodine in the biosynthesis of thyroid hormones.
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    URL: http://dx.doi.org/10.1007/BF02265858
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    Retention of 1,ω-bis-(dialkylamino)-polysulphides and related compounds in reversed-phase HPLC (1989)
    Springer
    Chromatographia 27 (1989), S. 113-117 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention contribution of nitrogen ; Effect on methylene and sulphur chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of secondary amines R2NH with disulfur dichloride S2Cl2 in dichloro methane yields mixtures of bis-dialkylamino polysulphides R2N−Sn−NR2 with sulphur chain lengths varying from ns=2 to 14. The S chains are believed to be non-branched. The compounds form homologous series in each of which sulphur atoms give a constant contribution to retention. The sulphur retention index depends slightly on the carbon number in the terminal alkyl groups R. The presence of nitrogen lowers retention. The index increment of N is ca. −160 units, which is distinctly less negative than values found in alkylamines.
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    URL: http://dx.doi.org/10.1007/BF02265861
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    LC-MS of enzymatic peptic haemoglobin hydrolysate produced at the pilot-plant level (1989)
    Springer
    Chromatographia 27 (1989), S. 128-134 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size-exclusion chromatography ; Fast atom bombardment-MS ; Peptic haemoglobin hydrolysate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the ready identification of any peptide isolated from a complex peptic haemoglobin hydrolysate produced on the pilot-plant scale. A combination of size exclusion and reversed-phase, high-performance liquid chromatography have proved to be a useful strategy for fractionation of such a mixture. This technique enabled pure peptides from the total hydrolysate to be obtained. Amino acid analysis and fast atom bombardment mass spectrometry provided the accurate composition and molecular weight of any isolated peptide. Molecular weights are compared with those deduced from size-exclusion chromatography (SEC) and the usefulness of SEC is discussed. The procedure described in this study will be useful for acquiring a better knowledge of such an hydrolysate and could be extended to other crude protein digests.
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    URL: http://dx.doi.org/10.1007/BF02265864
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    Chromatographic and potentiometric determination of dissociation constants of weakly basic Aroma compounds (1989)
    Springer
    Chromatographia 27 (1989), S. 194-200 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dissociation constants ; Potentiometric titration ; 2,4-Dimethylthiazole ; Trimethylpyrazine ; Methyl anthranilate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase liquid chromatography on two stationary phases—octadecylbonded silica Partisil ODS-3 and polystyrene-divinylbenzene resin PRP-1—and potentiometric titration in the water/methanol mobile phase were investigated in order to determine the dissociation constants of three weakly basic aroma compounds, namely trimethyl pyrazine, 2,4-dimethyl thiazole and methyl anthranilate. The data obtained from both methods are quite consistent and compare favourably to values found in the literature.
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    URL: http://dx.doi.org/10.1007/BF02260445
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    Rapid reversed-phase chromatographic separation and determination of selenum and tellurium (1989)
    Springer
    Chromatographia 27 (1989), S. 292-296 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Selenium(IV)-tellurium(IV) separation ; Flow-through coulometric detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of selenium and tellurium has been investigated with two different reversed-phase chromatographic methods, using P-350 (methyl-bi-isooctyl phosphate) and TBP (tributyl phosphate) as the stationary phases. HCl, HBr, NaCl and NaBr were employed as mobile phase components in both methods. The results suggested that the separation mechanism corresponds to the formation of TeCl (or TeBr) and P-350H (or TBPH) ion associate. A coulometric flow-through detector was applied to determine Se(IV) and Te(IV). Complete separation and quantitative determination of Se and Te could be achieved in 10 minutes.
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    URL: http://dx.doi.org/10.1007/BF02321271
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    Selectivity of alkyl-bonded phases in reversed-phase liquid chromatography of hydrophobic compounds (1989)
    Springer
    Chromatographia 27 (1989), S. 371-377 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alkyl-bonded silica gel ; Enthalpy ; Van der Waals volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Starting from silica gel with a purity of 99.999%, octadecyl-(ODS), octyl-(C8) and propyl-(C3) bonded silica gels were synthesized, and end-capped by trimethyl groups. The pore size was 150 Å and the specific surface area was 320 m2/g. The ODS and C8 silica gels were stable in both acidic and basic solutions. The selectivity of these bonded-silica gels was examined from the difference of the retention behavior of alkanes (Al−Al), alkylbenzenes (Ph−Al), alkylalcohols (Al−OH) and polyaromatic hydrocarbons (PAH) in aqueous acetonitrile. On these packings the log k′ values decreased in the order Al−Al〉Ph−Al〉PAH〉Al−OH. Furthermore, the chromatographic behavior of these compounds was measured on polymer-coated octadecyl-bonded silica gel (CAP) and octadecyl-bonded vinyl alcohol copolymer gel (ODP). The selectivity was verified from the value of R* of these compounds: $$R = R_v + R^* $$ where R is the retention time, and Rv is the retention time of an alkane having the same Van der Waals volume as the analyte. The R* values indicated that this ODS had more selectivity than C8 and C3, however R* on C8 showed a very good correlation with R* on C3. Their retention behavior on CAP was similar to that of ODS, however, their capacity ratios measured on CAP were smaller than those on ODS. The ODP has selectivity for the retention of aromatic compounds, because PAHs were retained strongly on this column.
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    Determination ofAlternaria mycotoxins in foodstuffs by gradient elution liquid chromatography with electrochemical detection (1989)
    Springer
    Chromatographia 27 (1989), S. 425-430 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alternaria mycotoxins ; Food analysis ; Electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The electroactivity of majorAlternaria mycotoxins has been explored in order to devise a liquid chromatographic-electrochemical detection (LC-EC) method for the determination of these toxic metabolites in fungal cultures and in naturally contaminated foodstuffs. Alternariol, alternariol methyl ether, altertoxin-I and altertoxin-II have been found to be electroactive and could be detected at sub-nanogram levels. Advantages and limitations of dual electrode (screen mode) coulometric detection and single electrode amperometric detection are presented and discussed. The feasibility of electrochemical detection in gradient elution liquid chromatography as well as its applicability to the analysis of contaminated foodstuffs is demonstrated.
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    Automatic measurement of some common herbicides by LC using simultaneous UV detection and electrochemical detection in series (1989)
    Springer
    Chromatographia 27 (1989), S. 431-435 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV diode array detection ; Electro chemical detection ; Herbicides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automated procedure is described for simultaneous UV detection at three different wavelengths and electro chemical detection in series of some residual herbicides. UV spectra of nine compounds of different compound groups are presented. Liquid-liquid extraction with dichloromethane and an enrichment of about one thousandfold has been used. Recovery rates after enrichment and detection limits of four s-triazine, three phenyl urea herbicides, metazachlore and metamitrone in river and drinking water are shown. It is concluded that the herbicides examined can be detected at levels between 10ng l−1 and 50ngl−1, without the necessity of derivatisation or clean-up processes.
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    Separation and purification of porcine pancreatic enzymes by serial operation of ion-exchange and affinity columns (1989)
    Springer
    Chromatographia 27 (1989), S. 449-454 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange and affinity columns in series ; Porcine pancreatic enzymes ; Trypsin and elastase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to separate and purify some of the enzymes contained in porcine pancreas, operation of an ion-exchange column in series with an affinity column has been used. The enzymes dealt with possess very similar molecular weights, isoelectric points and active sites. Hence they are difficult to separate and purify by traditional separation and/or purification methods. CM-Sepharose anion-exchange resin adsorbs elastase and trypsin at low pH (4.5) and desorbs them at high pH (9.0) and high ionic strength. Chitin-CHOM affinity adsorbent adsorbs trypsin at high pH (8.0) and desorbs it at low pH (2.5). By virtue of this complementary relationship two chromatographic columns were connected in series for facilitating the separation and purification of elastase and trypsin from porcine pancreas. The result showed that the specific activities of elastase and trypsin had been increased 16 and 22 fold respectively.
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    Determination of atmospheric ammonia as m-toluamide by denuder sampling and HPLC-UV detection (1989)
    Springer
    Chromatographia 28 (1989), S. 27-30 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Atmospheric ammonia ; m-Toluamide derivative ; Annular denuder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and reliable method for routine measurement of ammonia in ambient air is described. It is based on the collection of ammonia on H3PO3-coated annular denuders and its subsequent derivatization withm-toluoyl chloride (MTC) in alkaline acetonitrile. The resultingm-toluamide is determined by reversed phase HPLC with UV detection at 230 nm. The limit of dotection is about 0.3μg m−3 for NH3 in air samples collected at 151 min−1 for one hour.
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    High-performance-liquid chromatography ofThermus aquaticus 50S and 30S ribosomal proteins (1989)
    Springer
    Chromatographia 28 (1989), S. 39-44 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thermus aquaticus ; Ribosome ; 50S and 30S subunit proteins ; Gel electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ribosomal 50S and 30S subunit proteins (r-proteins) ofThermus aquaticus have, for the first time, been characterized by size exclusion chromatography (SEC) and by reversed phase high performance liquid chromatography (RPC). To ensure that the best resolution in the RPC was obtained. the elution conditions, such as gradient time, flow rate, temperature, ionic strength of the eluent and the type of stationary phase were optimized. Correlation between experimentally found retention times and those predicted by DryLab G was better than 0.7% over 30 peaks. Protein fractions from RPC runs were desalted and processed by gel electrophoresis so that the ribosomal proteins could be identified by their position on SDS-polyacrylamide gels. The enhanced speed and quality of separation which has been achieved in this study is expected to bring advantaces in experimental work with ribosomal proteins as well as with other biopolymers. In our case the high resolution technique provides a basis for the preparation of a collection of individual ribosomal protein components for future rRNA-protein interaction studies.
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    Polymer coated stationary phases for liquid chromatography (1989)
    Springer
    Chromatographia 28 (1989), S. 19-23 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preparation of stationary phases ; Polymer coated stationary phases ; Polymer-octyl bonded phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polymethyloctylsiloxane-coated stationary phases have been prepared for liquid chromatography, by thermal reaction. The influence of the reaction conditions on retention and efficiency of test substances with different structures has been discussed. The materials have good stability in both acidic and basic eluents.
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    HPLC and electrophoresis — Competitors or partners (1989)
    Springer
    Chromatographia 28 (1989), S. 89-91 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrophoresis ; Comparison of HPLC and electrophoresis ; Proteins, peptides and amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Protein structure analysis is an indispensible tool in modern biological research. However, the isolation of a protein or the separation of peptides in a form suitable for sequence analysis is a considerable technical challenge. The two predominant separation methods in protein biochemistry are chromatography and electrophoresis. In this paper the position, advantaged and disadvantages of both HPLC and electrophoresis for the separation of amino acids, peptides and proteins in protein structure analysis are discussed.
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    Simultaneous determination of pseudouridine and creatinine in urine by HPLC with polarographic detection (1989)
    Springer
    Chromatographia 28 (1989), S. 605-609 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detection ; Pseudouridine ; Creatinine ; Urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The anodic behaviour of pseudouridine a modified nucleoside proposed as tumoral marker, has been studied at a mercury electrode. A method for its determination in urine samples by liquid chromatography with indirect anodic polarographic detection has been developed. The method is simple, highly selective and permits the direct injection of urine after dilution (1∶20) with mobile phase. Creatinine, which also gave an anodic response on mercury, could be simultaneously determined and used as an “internal standard” for Psi. This allowed the pseudouridine/creatinine ratio determination in a single run on the same specimen and the use of urine samples collected randomly instead of the 24h collection. The within-day RSD% for pseudouridine/ creatinine peak areas ratio was 3.4%.
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    Evaluation of synthetic procedures for the chemical modification of alumina for HPLC (1989)
    Springer
    Chromatographia 28 (1989), S. 565-568 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; New bonded phases ; Alumina ; Protein separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several reactions are tested for the chemical modification of alumina. These include the following: chlorination of the surface hydroxyls followed by reaction with an organolithium compound; chlorination of the surface hydroxyls followed by reaction with a Grignard reagent; chlorination of the surface hydroxyls followed by reaction with an amine; chlorination of the surface hydroxyls followed by reaction with an alcohol; direct reaction of the alumina with an organochloroalane and direct reaction of the alumina with an alcohol. Only the first reaction gave a product which contained enough bonded organic material to be easily detected by FTIR. Preliminary stability tests show that the product of the first reaction retains the bonded organic material when exposed to nonpolar and polar organic solvents as well as aqueous solutions of pH 1.0, 7.0 and 12.0. Chromatographic testing establishes reversed-phase behavior for alkylarylketones as solutes and the bonded phase displays good biocompatibility for a series of protein standards.
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    Separation of adenosine triphosphate and its degradation products in innervated muscle of the frog by reverse phase high-performance liquid chromatography (1989)
    Springer
    Chromatographia 28 (1989), S. 610-612 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine phosphates ; Adenosine phosphate degradation products ; Innervated frog muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Adenosine mono-, di- and triphosphates, inosine monophosphates, adenosine, inosine and hypoxanthine were separated in a single run by high-performance liquid chromatography with UV detection. AC-18 reversephase column was used. An isocratic elution with 100mM phosphate buffer (KH2PO4) pH6.5 and 1.2% methanol, followed by a 5 minute linear gradient up to 15% methanol after the 10th minute was performed during each run with a flow rate of 1.25ml/min. The time required for each analysis was 25 minutes. The detection limit for each substance ranged from 3 to 5 pmol. All the substances under study were detected in the incubation medium when adenosine triphosphate was exogenously applied to the innervated frog sartorius muscle.
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    Analysis of preservatives in cosmetics—Methylisothiazolones (1989)
    Springer
    Chromatographia 28 (1989), S. 34-38 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Methylisothiazolones ; Preservatives ; Analysis of cosmetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Antimicrobially active formulations based on 2-methyl-3(2H)-isothiazolone and 5-chloro-2-methyl-3(2H)-isothiazolone (Kathon CG, Euxyl K 100) are incorporated into manufactured cosmetics as preservatives. In this paper we report on the analysis of these active components by means of liquid chromatography. It is conventional for the original methylisothiazolone components in cosmetics to be analyzed by reversed phase high-performance liquid chromatography after column chromatographic separation and flash chromatographic purification. In our new analytical method the methylisothiazolones are converted into the respective β-thiosubstituted acrylamide derivatives, which are ionic substances, with the help of the nucleophilic reagent hydrogensulfite. An ion pair high-performance liquid chromatographic method has been developed for the separation and quantification of these derivatives.
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    Molecular interactions in liquid adsorption chromatography with mixed mobile phase. Solvation of the chromatographed substance in a ternary mobile phase (1989)
    Springer
    Chromatographia 28 (1989), S. 151-156 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular interactions ; Association effects ; Analyte solvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The linear Jaroniec equation has been utilized for the description of chromatographic systems in which the test substance molecule is solvated by the solvent molecules. A possibility of the formation of multimolecular solvates in the bulk phase has been confirmed. The measurements were made using liquid adsorption chromatography with ternary mobile phase.
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    HPLC Analysis of complex mixtures of triglycerides using gradient elutions and an ultraviolet detector (1989)
    Springer
    Chromatographia 28 (1989), S. 183-188 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Triglycerides ; Gradient elution ; UV detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method of reserved-phase HPLC analysis for mixtures of triglycerides (TG's) that provides good resolution at acceptable analysis times for high-ECN TG's has been developed. An elution gradient of methyltert-butyl-ether (MTBE) in acetonitrile (ACN) was used with an ultraviolet detector operated at 215nm. The effect of the proportion of MTBE in the mobile phase, gradient time, temperature and sample solvent on TG retention and resolution was studied. Linear relationships were derived between the logarithm of the capacity factor (log k'), and the logarithm of selectivity (log α) and the above-mentioned chromatographic factors. The conditions selected were: an elution gradient of from 23 to 30% MTBE, an elution gradient time of 25 minutes, and a temperature of 30°C, which provided good resolution of soybean oil TG's in less than 30 minutes.
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    Determination of potential degradation products of piroxicam by HPTLC densiometry and HPLC (1989)
    Springer
    Chromatographia 28 (1989), S. 197-202 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Piroxicam ; Piroxicam degradation products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPTLC densitometry and HPLC are considered for the simultaneous determination of the degradation products of piroxicam (2-aminopyridine, DP-I and DP-II). The substances were separated on silica gel with fluorescence indicator in ethylacetate — toluene — diethylamine (10∶10∶5) and toluene — absolute ethanol — glacial acetic acid (8∶1.2∶0.5) systems. The measuring absorbance (detection of reflectance) of the separated substances was carried out “in situ” at 296 nm using 4-level calibration (external standard, nonlinear regresson function) in the concentration range 600–1200 ng 2-aminopyridine/spot and 300–600 ng DP-I and DP-II/spot. The HPLC method was carried out using RP-8 stationary phase and methanol + phosphate-citrate buffer, pH 3 mobile phase with addition of sodium pentanesulfonate (40+60, v/v). 2-aminopyridine wass detected at 300 nm, DP-I at 280 nm and DP-II at 248 nm. The concentration range for 2-aminopyridine is 2–40 μg/ml, for DP-I and DP-II 2–20 μg/ml (for an injection volume of 10 μl). The results were evaluated by linear regression analysis.
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    Chiral bonded packings for liquid chromatography: Preparation and evaluation of N-acylated aminoacid packings based on aminopropylated silica gel (1989)
    Springer
    Chromatographia 28 (1989), S. 212-216 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral bonded phases ; Enantiomer separations ; Amino acid esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary N-Protected single amino acid residues have been chemically bound to aminopropylated silica gel to give chiral HPLC column packings. Surface coverages have been determined by both elemental and aminoacid analyses. In addition, the nature of the surface-bound groups has been studied by reflectance fourier transform infrared (FTIR) spectroscopy. The resolution of a range of racemic mixtures has been achieved using the column packings.
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    Enantiomerization during HPLC on an optically active sorbent. Deconvolution of experimental chromatograms (1989)
    Springer
    Chromatographia 28 (1989), S. 263-266 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Triacetylcellulose ; Enantiomer interconversion ; Deconvolution of chromatograms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantiomers of 1,3,7-trimethylbenzo[c]phenanthrene, a chiral helicene hydrocarbon, are separated on triacetyl-cellulose but interconvert during HPLC. Column temperatures were between 2 and 22°C and linear velocities between 0.3 and 1.2 mm s−1. Simultaneous photometric and polarimetric detection resulted in deconvoluted experimental chromatograms, showing the relative concentration of each of the enantiomers as aseparate function of the retention volume. The use of deconvoluted chromatograms for determining rate constants of enantiomerization is discussed. It is of interest that the rate constant at 22.3°C in solution, i.e. in the absence of a sorbent, has been obtained by an independent method: stopped-flow monitoring of racemization after HPLC on triacetylcellulose.
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    The effect of an organic eluent modifier and pH on the separation of wheat-storage proteins: Application to the purification of γ-gliadins ofTriticum monococcum L (1989)
    Springer
    Chromatographia 28 (1989), S. 133-138 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wheat proteins ; γ-gliadins ; Effect of pH on separation ; Effect of organic modifier on separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, high-pressure liquid chromatography has been used to separate similar protein (γ-gliadin) components from 70% ethanol extracts of endosperm flour from two different accessions of the diploid wheatTriticum monococcum L. The effect of acetonitrile as the organic eluent was compared to acetonitrile: 2-propanol (3:1) at two different pH's. Conditions for maximum resolution of the γ-gliadin components were found to be at pH 7.2 with acetonitrile: 2-propanol (3:1) as the eluent. These conditions allowed the components to be obtained in sufficient purity for further charaterization.
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    Selective preconcentration on a metal loaded silica precolum and on-line HPLC separation of catechol derivatives in a complex medium. Application to the analysis of catecholamines in urine (1989)
    Springer
    Chromatographia 28 (1989), S. 459-464 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Catecholamines in urine ; Liquid-solid extraction ; Metal-loaded silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of iron loaded silica to selectively preconcentrate, by a chelating effect, catechol and its derivatives has been investigated. Parameters which can influence the breakthrough volume, such as minimum saturation concentration, variation of pH, ionic strength and flow rate of the preconcentrated phase are described. The coupling of this method with an ion-pairing chromatographic separation is demonstrated, several eluting solutions have been investigated. The influence of elution times, the linearity, the limit of detection and the recovery of the system are studied. This method has been applied to the quantitative determination of catecholamines in urine samples using 1,2-dihydroxybenzylamine as an internal standard.
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    Optical resolution HPLC column packings carrying penicillin sulfoxide nucleus. Part I. Polymer synthesis and resolution efficiency (1989)
    Springer
    Chromatographia 28 (1989), S. 505-508 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Optical resolution ; Polymeric adsorbents ; Penicillin sulfoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polyacryl or methacrylamides bearing penicillin sulfoxide skeleton were synthesized. The obtained polymers were coated onto macroporous silica gel and the properties of the prepared packings were investigated. The column packing comprising poly(benzyl 1-oxo-6-methacrylaminopenicillanate) was found to resolve various aromatic racemates.
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    Optical resolution HPLC column packings carrying penicillin sulfoxide nucleus. Part IV. Effect of substituents in the benzyl ester group on the optical resolution efficiency (1989)
    Springer
    Chromatographia 28 (1989), S. 513-515 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Optical resolution ; Polymeric adsorbents ; Penicillin sulfoxide ; Substituent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fourteen new vinyl polymers carrying penicillin sulfoxide nucleus, poly (substituted-benzyl 1-oxo-6-metha-crylaminopenicillanate)s, were synthesized in order to investigate the influence of the substituents on the optical resolution capabilities. The resolution efficiency of the high-performance liquid chromatography columns comprising the obtained polymers were examined usingtrans-stilbene oxide and N-acetyl-1-phenethyl-amine. It was found that some columns resolved both racemates, some one, while the others did not separate either. A polymer which has 2,6-dichlorobenzyl moiety was found to resolve both racemates more effectively than the unsubstituted polymer.
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    High-performance liquid chromatographic resolution of enantiomers on chiral epoxy polymer-coated silica gel (1989)
    Springer
    Chromatographia 28 (1989), S. 477-480 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phase ; Resolution of amino acid derivatives ; Enantioseparation by HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chiral stationary phase for the separation of some D-and L-amino acid derivatives using a new resolving agent is described. The enantiomeric resolution was accomplished by normal phase high-performance liquid chromatography. The support was easily prepared by coating an epoxy polymer of L-valinamide on aminopropylsilanized macroporous silica. The influence of subambient temperatures on the enantioselectivity was also examined.
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    Optical resolution of 2-hydroxy acids by high-performance ligand exchange chromatography (1989)
    Springer
    Chromatographia 28 (1989), S. 481-486 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand exchange ; Chiral phase ; Optical resolution of 2-hydroxy acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using an MCl GEL CRS10W column, which was packed with octadecyl silica (ODS) coated with N,N-dioctyl-L-alanine, optical resolution of 2-hydroxy acids was performed. The optical resolution of mandelic acid derivatives and C2 to C5 2-hydroxy acids was carried without any pretreatment. The MCl GEL CRS10W column could resolve amino acids and 2-hydroxy acids. For their selective detection, a post-column method was employed in which the specific color reaction of 2-hydroxy acids with iron(III) ion was utilized. For the analysis of foodstuffs, in which amino acids and 2-hydroxy acids often coexist, the present method was found to be effective in distinguishing between these enantiomers.
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    Isolation and quantitative analysis of hydroxylysine glycosides (1989)
    Springer
    Chromatographia 28 (1989), S. 497-501 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Collagen metabolites ; Amino acid derivatives ; Glycosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methods are described for the isolation of galactosyl hydroxylysine and glucosylgalactosyl hydroxylysine from collagen and for the quantitative analysis of these hydroxylysine glycosides. The isolation procedure, based upon gel filtration and preparative ionpaired reversed-phase high-performance liquid chromatography, is simple and rapid in comparison with existing methods, allowing the production of tens of milligrams of each glycoside in a single day. Quantitative analysis of the hydroxylysine glycosides is effected by reversed-phase high-performance liquid chromatography with precolumn derivatization (usingo-phthal-dialdehyde) and fluorescence detection.
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    A practical description of retention in reversed phase chromatography using four parameters (1989)
    Springer
    Chromatographia 27 (1989), S. 5-14 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention behaviour ; Column parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of small molecules on reversed phase or other hydrophobic stationary phases can be represented by k′ values of members of a homologous series at varying solvent compositions. The evaluation of simple linear relationships leads to the introduction of a set of four parameters that contain all the information about retention behaviour of this homologous series in the binary solvent system chosen. It is possible to extrapolate to a hypothetical non-hydrophobic molecule and a solvent, the polarity of which equals that of the stationary phase, to characterize the properties of the stationary phase — eluent system. In addition, a chromatographic method for determination of the phase ratio of the column is proposed.
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    Energy calculations and computer modeling of chromatographic separations on microcrystalline cellulose triacetate (1989)
    Springer
    Chromatographia 27 (1989), S. 77-81 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microcrystalline cellulose triacetate ; Molecular modeling ; Computer graphics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Molecular modeling and energy calculations have been used to study the chromatographic separation of aromatic compounds on microcrystalline cellubose triacetate. A linear relationship has been found between the logarithms of the capacity factors and the energy values of the interaction of these compounds with this stationary phase. The interaction energies have been calculated for two different spatial dispositions of the solutes in relation to the sorbent.
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    A chemically bonded liquid crystal as a stationary phase for high performance liquid chromatography. Synthesis on silica via an organochlorosilane pathway (1989)
    Springer
    Chromatographia 27 (1989), S. 559-564 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid crystals ; Synthesis of new bonded phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A compound which becomes a liquid crystal when bonded to a polysiloxane was reacted with dimethylchlorosilane to produce a reagent suitable for bonding to a silica surface. After the silanization reaction was complete, the product was characterized by elemental analysis, diffuse reflectance Fourier transform Infrared Spectroscopy (DRIFT), CP/MAS carbon-13 NMR and differential scanning calorimetry (DSC). Preliminary chromatographic testing was done by retention index measurements using the alkylarylketone homologous series and by measuring the separation factor, α, for anthracene/phenanthrene at two different mobile phase compositions.
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    Preparative medium pressure liquid chromatographic (MPLC) and semipreparative HPLC separation of furocoumarin isomers (1989)
    Springer
    Chromatographia 27 (1989), S. 591-595 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Overpressured layer chromatography ; Furocoumarin isomers ; Preparative separation of plant extracts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Preparative medium pressure liquid chromatography and semi-preparative high performance liquid chromatography on silica were employed for the isolation of eight furocoumarin isomers (iso-bergapten, angelicin, psoralen, bergapten, pimpinellin, sphondin, xanthotoxin and isopimpinellin). The conditions were transposed from analytical on-line overpressured layer chromatography and analytical high performance liquid chromatography, respectively. The retention data of the analytical on-line overpressured layer chromatographic separation and the preparative medium pressure liquid chromatographic isolation show a linear relationship. Using 15 μm TLC silica 60 as stationary phase a dry-packing procedure aas developed for labomatic medium pressure liquid chromatographic glass columns. The efficiency of the preparative separation techniques was demonstrated by the isolation of the investigated furocoumarins from Heraclei mantegazziani radix and from Pimpinellae radix (Balkan quality).
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    Prediction of HPLC retention times in gradient elution from isocratic data application to a set of non-homologous compounds and different stationary phases (1989)
    Springer
    Chromatographia 27 (1989), S. 19-23 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Prediction of retention times ; Gradient elution ; Substituted quinolines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chromatographic model able to predict, from experimental isocratic data, retention times of solutes under gradient conditions has been proposed previously. The prediction was shown to be totally independent of the chemical properties of both solutes and eluents. In order to further check the general validity of the theory, the model has now been applied to a nonhomologous set of compounds, namely a range of substituted quinolines (methyl-, hydroxy- and amino-) and several different stationary phases. Results show a dependence on the stationary phase and, to a lesser extent, on the chemical structure of the solutes. The possible sources of errors are discussed. The generality of the method holds, within acceptable limits, if predictions concern the same type of stationary phase.
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    The case of the elusive tm values in HPLC (1989)
    Springer
    Chromatographia 27 (1989), S. 156-158 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mobile phase retention time ; Capacity factor ; Negative capacity factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Numerous ideas and procedures have been suggested in the literature for the determination of tm, the retention time of a non-retained species, in high-performance liquid chromatography. In some cases chromatograms have been obtained showing sample components eluting prior to the assumed non-retained species. This phenomenon results in apparent negative capacity factors for the species in question. We have proposed a method employing small inorganic anions which results in a limiting value for tm and eliminates apparent negative capacity factors.
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    Analysis of thiols by HPLC after fluorescent prelabelling with 4-(6-methylnaphthalen-2-yl)-4-oxobuten-2-oic acid (1989)
    Springer
    Chromatographia 27 (1989), S. 185-190 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thiol analysis ; Fluorimetric detection ; Derivatization with 4-(6-methylnaphthalen-2-yl)-4-oxobuten-2-oic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 4-(6-methylnaphthalen-2-yl)-4-oxobuten-2-oic acid as a fluorogenic reagent in pre-column derivatization for the high-performance liquid chromatography (HPLC) of biologically important thiols (L-cysteine, glutathione, N-acetylcysteine, homocysteine and mercaptopropionylglycine) was investigated. The aroylacrylic acid reacts selectively and rapidly (15 min. at room temperature) with the thiol compounds to give stable fluorescent adducts which can be separated by reversedphase HPLC and detected fluorometrically (λex 300nm); λem 445nm). The experimental conditions for the thiol derivatization and chromatographic separation are discussed. Applications to the determination of N-acetylcysteine, mercaptopropionylglycine and cysteine are described.
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    Retention behaviour of selected flavonoid compounds in NP-HPLC (1989)
    Springer
    Chromatographia 27 (1989), S. 625-627 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase elution ; Silica and cyano columns ; Flavonoid compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC retention data for a number of flavonoid compounds have been evaluated on normal phase silica and cyano colums according to the Soczewinski-Snyder (S.-S.) model. On the silica phase most of the flavones examined exhibited asymetrical peak shapes indicating strong and mixed retention mechanisms; on the cyano phase the intercept of the S.-S. relationship was independent of any hydroxy substitution pattern or of molecular planarity. A similar behaviour, but with different intercept values, was observed with coumarin and quinone compounds.
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    Preparative HPLC of carotenoids (1989)
    Springer
    Chromatographia 27 (1989), S. 325-327 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carotenoid ; Xanthophyll ; Broccoli ; Paprika
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the preparative HPLC of up to 50mg of carotenoid using a self-packing axially-compressed column. Oxygenated carotenoids, xanthophylls, are separated with silica as the stationary phase and acetone/petroleum ether as the mobile phase, while carotenes are separated using magnesium oxide/polyamide as the stationary phase and undiluted petroleum ether as the mobile phase.
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    Applications of HPLC with evaporative light scattering detection in fat and carbohydrate chemistry (1989)
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    Chromatographia 27 (1989), S. 340-342 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Evaporative light scattering detection ; α, ω-Dicarboxylic and hydroxycarboxylic acids ; Alkylglucosides and glycerides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The advantages of an evaporative light scattering detector in HPLC are demonstrated using the separation of α, ω-dicarboxylic and hydroxycarboxylic acids, alkyl glucosides and mono-, di- and triglycerides as examples. By using this detector reversed phase as well as normal phase gradient HPLC becomes possible for substances with no UV absorption.
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    Preparation of silica-based cation-exchangers for use in ion chromatography (1989)
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    Chromatographia 27 (1989), S. 316-320 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Silica-based cation-exchanger ; Trimethylsilyl chlorosulfonate ; Lanthanides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A low exchange-capacity, silica-based cation-exchanger for use in ion chromatography has been synthesized. (p-Trimethylsilyl)benzyl-dimethylchlorosilane (TBDCS) reacts with trimethylsilyl chlorosulfonate (TMCS) to produce a compound sulfonated in the para position of the type ArSO2OSi (CH3)3, which is bonded to 5 μm porous silica beads and hydrolysed to the corresponding arylsulfonic acid. The product is hydrophilic and has a high degree of sulfonation, efficiencies of packed columns reaching about 40,000–50,000 plates per meter for the separation of the Mn2+ ion. The new stationary phase has been applied to the ion chromatography of some organic and inorganic ions. It is notable that 14 lanthanides can be separated by isocratic elution about one hour on a 150×4·6 mm column, with 4 mM ethylenediamine and 6 mM α-hydroxyl-isobutanoic acid (pH 3.67) as mobile phase.
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    Enhanced chemiluminescence detection of some dansyl amino acids in liquid chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 191-193 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dansyl amino acids ; Chemiluminescence ; Bis(2,4,6-Trichlorophenyl)oxalate, (TCPO) ; Enhancement of luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The dansylated amino acids alanine, glutamic acid, methionine and norleucine were separated by reversedphase HPLC and detected via chemical excitation using the post-column, TCPO-peroxyoxalate reaction system. Enhancement of the chemiluminescence emission was achieved by including the surfactant Triton X-100 in the eluent.
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    Measurement of elastin hydrolysis by reverse-phase HPLC with on-line post-colum derivatization (1989)
    Springer
    Chromatographia 27 (1989), S. 225-227 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reverse-phase chromatography ; Elastin Hydrolysis measurement ; On-line post-column derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Excessive breakdown of elastin, a structural protein, may be related to aortic disease and emphysema. Since L-valyl-L-proline occurs in high concentrations in elastin, a rapid and sensitive method using HPLC with post-column on-line derivatization was used to measure the dipeptide from swine aortic tissue, and the amount of elastin present was determined. Elastin was extracted by alkaline hydrolysis. After neutralization and filtration, the sample was injected onto a ODS-2 gel column, and the dipeptide was eluted by a linear gradient of 0 to 10% of 1-propanol in 50 mM heptafluorobutyrate, pH 3, at a flow rate of 1 ml/min. The eluent was reacted with fluorescamine at pH 8.6, and fluorescence was detected at an excitation wavelength of 395 nm and a 455 nm cutoff emission filter.
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    Anion exchange behaviour of hydrous titanium oxide and its use for column separations (1989)
    Springer
    Chromatographia 27 (1989), S. 472-474 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrous titanium oxide ; Anion exchange ; Polyvalent anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hydrous titanium oxide (HTiO), prepared under varying conditions of precipitation, has been studied for its anion exchange behaviour. Its chemical and thermal stability has been examined. The stoichiometry of uptake for Cl− has been investigated using a36Cl radiotracer and the regeneration power of the exchanger checked. Distribution coefficients for halides and polyvalent anions have been determined and on the basis of sorption data some polyvalent anions have been separated using HTiO columns.
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    An improved HPLC determination of flavonoids in medicinal plant extracts (1989)
    Springer
    Chromatographia 27 (1989), S. 509-512 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flavonoids ; Crataegus ; Passiflora ; Matricaria ; Ginkgo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Flavonoids of Crataegus monogyna, Passiflora incarnata, Matricaria chamomilla and Ginkgo biloba extracts have been separated by isocratic elution on C18 columns using eluents based on C3 alcohols, tetrahydrofuran or dioxane. Satisfactory results have been obtained at compared to the low resolution achieved with the customary system acetonitrile-water-acetic acid.
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    Chromatography based on membrane separation with vesicular packing material (1989)
    Springer
    Chromatographia 28 (1989), S. 561-564 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion ; Vesicular packing material ; Proteins and polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new vesicular packing material — prepared from plant cell clusters by purification of the intact cell wall framework —is suitable for chromatography, giving high performance at low pressure gradients. The separation is achieved by dialysis through the cell wall, which is an ultrafilter membrane with an extremely sharp size limit of separation. Almost the whole of the stationary liquid phase is located within the vesicle (empty cell) lumina. In contrast to gel filtration vesicle chromatography gives a practically ideal separation of two size groups with an extremely short fractionation range. The size limit of separation was investigated by chromatography of proteins and other polymers. Group separation of molecules of a polydisperse dextran standard preparation showed that the critical Stokes' diameter for dextran permeation into the stationary liquid phase of the vesicular packing is 5 to 6 nm.
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    URL: http://dx.doi.org/10.1007/BF02260677
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    Semi-preparative high-performance liquid chromatographic separation of four 1.1-dimethylethyl 4- and 5-bromo-trans-2-methylcyclohexane-1-carboxylate isomers (1989)
    Springer
    Chromatographia 28 (1989), S. 585-587 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preparative scale separation ; 1,1-Dimethylethyl 4- and 5-bromo-trans-2-methylcyclohexane-1-carboxylate ; Trimedlure-related isomers ; Ceratitis capitata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A semi-preparative high-performance liquid chromatographic procedure on 5-μm silica was developed for the isolation of gram quantities of four 1,1-dimethylethyl 4- and 5-bromo-trans-2-methylcyclohexane-1-carboxylate isomers (trimedlure-related) for NMR studies and comparative biological evaluation as male medfly,Ceratitis capitata, attractants.
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    URL: http://dx.doi.org/10.1007/BF02260682
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    Applications of chromatographic and spectrometric techniques to the study of dexamethasone related compounds (1989)
    Springer
    Chromatographia 28 (1989), S. 623-630 
    Details
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Column liquid chromatography ; Dexamethasone related compounds ; Mass spectrometry ; Illicit drug formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A methodology for the analysis of dexamethasone and related compounds is proposed. Nine corticoids (corticosteroids) have been separated by TLC and by normalphase HPLC. The optimization of the HPLC separation is performed on a diol column and with a n-hexane/isopropanol (80:20) mobile phase. Mass spectrometry is used to elucidate the nature of the compounds isolated from illicit drug formulations and to confirm the structure of synthesised derivatives from the parent dexamethasone.
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    URL: http://dx.doi.org/10.1007/BF02260691
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    Nucleotide and aldehyde analysis by HPLC for determination of radical induced damage (1989)
    Springer
    Chromatographia 28 (1989), S. 65-68 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxygen radicals ; Nucleotides ; Aldehydes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The analysis of two metabolite groups, nucleotides and aldehydes, is necessary for assessment of oxygen radical metabolism during hypoxia and reoxygenation. Nucleotides and their derivatives were determined by HPLC using gradient elution with 10 mM NH4H2PO4 buffer containing 2 mM t-butylammoniumphosphate and acetonitrile. Aldehydes occuring after lipid peroxidation were analyzed by derivatisation to dinitrophenylhydrazones followed by TLC and HPLC separation with methanol/water on an ODS column.
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    URL: http://dx.doi.org/10.1007/BF02290385
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    Requirements and tests for HPLC apparatus and methods in pharmaceutical quality control (1989)
    Springer
    Chromatographia 28 (1989), S. 85-88 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Quality assurance ; Pharmaceutical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary One possible method has been demonstrated for pharmaceutical quality control which is not restricted to this field and fulfils and documents the prerequisites for reliable, accurate and precise HPLC analysis. This includes validation which shows that the method is able in principle to fulfil the requirements, the apparatus test which shows that the apparatus generally works correctly and precisely and the system suitability test which shows that the method provides accurate and precise results on this apparatus and with this column for the analysis in question when other non-equipment and non-method-induced errors are excluded.
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    URL: http://dx.doi.org/10.1007/BF02290388
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    Immobilized enzymes as chromatographic phases for HPLC: The chromatography of free and derivatized amino acids on immobilized trypsin (1989)
    Springer
    Chromatographia 28 (1989), S. 551-555 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separations ; Trypsin on silica ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new HPLC stationary phase was synthesized by the covalent immobilization of the enzyme trypsin (TRYP) on silica. The hydrolytic activity of the immobilized enzyme was 72% of the activity of an equivalent molar amount of free TRYP. The initial chromatographic studies indicate that this phase can be used for chiral separations of enantiomeric O- and N,O-derivatized amino acids which are natural substrates on TRYP and that the stereochemical resolutions are a result of the activity of the enzyme.
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    Effect of destruction of chemically bonded reversed phases by hexamethyldisilazane during end-capping (1989)
    Springer
    Chromatographia 28 (1989), S. 574-578 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases ; End-capping ; Destructive effects on bonded phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMS) have been used as a secondary deactivation (end-capping) reagents for packing materials for RP HPLC. Three types of chemically bonded phases (CBP) with different structures and different coverage densities were used. The destructive effects of HMDS on the coverage density of chemically bonded C18 and C8 phases is discussed.
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    URL: http://dx.doi.org/10.1007/BF02260680
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    Assay for methylnaltrexone in rat brain regions and serum by high-performance liquid chromatography with coulometric electrochemical detection (1989)
    Springer
    Chromatographia 28 (1989), S. 359-363 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Coulometric electrochemical detection ; Methylnaltrexone ; Rat brain and serum analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and sensitive method is described for the determination of methylaltrexone, a quaternary narcotic antagonist, in discrete rat brain regions and serum. Separation and quantitation are performed by reversedphase high-performance liquid chromatography with coulometric electrochemical detection. Perchloric acid extracts of the brain tissue or serum were passed through a normal-phase solid-phase extraction CN column, and methylnaltreexone was subsequently eluted with a mixture of absolute ethanol and 25mM trifluoroacetic acid. Methylnaltrexone gave a linear response over the range of 12.5–100ng in 1.0ml for cerebellar homogenates and 25–200ng in 50μl for serum. The average betweenassay coefficients of variation for methylnaltrexone from 1.0ml of cerebellar homogenate and 50μl of serum were 5.2 and 3.6%, respectively, over the concentration range studied. The within-assay coefficients of variation at 12.5ng/ml cerebellar homogenate and 25ng/50μl for serum were 7.4 and 4.6%, respectively. Analytical recovery of methylanyltrexone, added to cerebellar homogenate and serum samples, were 85 and 89%, respectively. The method was applied to the analysis of methylnaltrexone in discrete rat brain regions and serum after intraperitoneal injection.
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    URL: http://dx.doi.org/10.1007/BF02261014
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    Preparative scale reversed-phase HPLC method for simultaneous separation of carotenoids and carotenoid esters (1989)
    Springer
    Chromatographia 28 (1989), S. 129-132 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carotenoids ; Paprika, Rose hips, Marigold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the preparative HPLC of carotenoids and carotenoid esters using a self-packing axially-compressed column. The reversed-phase system used employs an RP-18 stationary phase and a mobile phase consisting of a mixture of petroleum spirit, acetonitrile, methanol and tetrahydrofuran. The method is demonstrated for paprika fruit, rose hips and marigold flowers.
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    Retention characteristics of aliphatic compounds on cellulose acetates as a stationary phase with an aqueous mobile phase (1989)
    Springer
    Chromatographia 28 (1989), S. 279-284 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cellulose acetate ; Acetyl content ; Temperature effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Cellulose and cellulose mono-, di-, and triacetate were used as stationary phases for liquid chromatography with water as a mobile phase, and the retention behavior of alcohols, ethers, ketones, and chlorides was examined. For cellulose acetate columns, the logarithm of the specific retention volume, (logV g * ), correlated linearly with the logarithm of partition coefficient between 1-octanol and water (log Ko/w), for each homologous group, but all solutes were unretained on cellulose columns. With the exception of chlorides, the intercept values of the log V g * –log Ko/w regression lines increased significantly with increase of acetyl content of cellulose acetates, but the slopes of the regression lines changed little. This suggests that hydrophobic interaction between the acetyl groups of cellulose acetates and the alkyl chains of the solutes is the dominant factor in the retention. The capacity factors for 1-alcohols with cellulos diacetate column indicated a maximum at a column temperature of about 40°C. This unique retention behavior was assumed to be caused by small structural change of the cellulose acetate polymer, because this temperature effect on the retention corresponded with effects observed by differential scanning calorimetry (DSC).
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    Chromatographic investigations of furocoumarins fromHeracleum genus fruits (1989)
    Springer
    Chromatographia 28 (1989), S. 161-166 
    Details
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Column liquid chromatography ; Micropreparative separations ; Furocoumarins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Furocoumarins from extracts ofHeracleum genus fruits were separated using normal and reversed phase TLC and HPLC and isolated in the milligram scale using overloaded systems of column chromatography. Binary or ternary solvents containing a polar modifier (methanol, diisopropyl ether or acetonitrile) were used as the mobile phases.
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    Influence of mobile phase composition on the adsorption of hen egg-white proteins to anion-exchange cellulose (1989)
    Springer
    Chromatographia 28 (1989), S. 170-178 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange ; Mobile phase optimisation ; Egg-white proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Factors influencing the capacity of Whatman QA52 anion-exchange cellulose for hen egg-white proteins have been investigated. While simply increasing the concentration of protein in the feedstock increases the loading there is a concomitant reduction in binding efficiency in a single pass through the column. Substitution of buffer by water in the mobile phase during sample preparation, thereby reducing the ionic strength of the feedstock, had the effect of significantly increasing protein capacity whilst improving binding efficiency. During column loading large changes in pH of the mobile phase were observed although this had no apparent effect on the chromatography for this system.
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    URL: http://dx.doi.org/10.1007/BF02319642
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    A chromatographic method for hydrophobicity investigations of sorbents (1989)
    Springer
    Chromatographia 28 (1989), S. 258-262 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bonded stationary phases ; Evaluation of the hydrophobicity of sorbents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The energy of interaction (∈0) between the methylene group and the surface of a sorbent is proposed for use in the quantitative evaluation of the hydrophobicity of a sorbent. A method was developed to determine the ∈0 parameter from chromatographic measurements using the investigated sorbent as the stationary phase and linear methylene-containing homologous series, e.g., alkanols, amino-alkanes, etc., as the test compounds. The effectiveness of this method is demonstrated by using, as examples, a series of bonded stationary phases and a series of cross-linked copolymeric sorbents differing in the concentration of the hydrophobic groups. The proposed method is compared with the Martin rule used extensively in the chromatography of oligomers.
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    Computer-assisted transposition of conditions in high-performance thin-layer chromatography to high-performance liquid chromatography for the separation of pesticides (1989)
    Springer
    Chromatographia 28 (1989), S. 285-288 
    Details
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Column liquid chromatography ; Mobile phase optimization ; HPTLC transposition to HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer-assisted method is presented for mobile phase selection for the optimal separation of pesticides by HPTLC and HPLC. The system is based on a plot of solute retention value and separation criterion vs. binary mobile phase composition for graphic optimization. The result of HPTLC can be transposed to HPLC for optimal separation. The transposition equation is given.
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    HPLC determination of the flavonoid glycosides fromBetulae folium extracts (1989)
    Springer
    Chromatographia 28 (1989), S. 311-312 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flavonoid glycosides ; Betula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main flavonoid glycosides ofBetulae folium extracts (quercetin-3-glucuronide, myricetin-3-galactoside, hyperosid, quercetin-3-arabinoside and quercetin-3-rhamnoside) have been separated by isocratic elution on a C18 Aquapore RP-300 column. Elution was performed with 17% isopropanol at pH 6.2 confirming the validity of this eluent for the analysis of the flavonoid glycosides.
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    Precolumn fluorogenic labelling of carboxylic acids with the use of N-(1-pyrenyl)-bromoacetamide and phase-transfer catalysis (1989)
    Springer
    Chromatographia 28 (1989), S. 367-369 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carboxylic acids ; Fluoregenic esterification ; Phase-transfer catalysis ; Ion pairing ; N-(1-Pyrenyl)-bromoacetamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary N-(1-Pyrenyl)-bromoacetamide, which is readily synthesized from 1-aminopyrene and bromoacetyl bromide, has proved to be an excellent derivatization reagent for carboxylic acids. A technique has been developed, based upon a reaction with the carboxylate as an ion pair in ethylene dichloride at 90 °C, which gives highly fluorescent ester derivatives, permitting quantitative determination by liquid chromatography of less than one pmol using conventional fluorimetric detection. Further, the method is highly reproducible and of general utility.
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    Application of diode array detectors for solute identification in toxicological analysis (1989)
    Springer
    Chromatographia 28 (1989), S. 341-353 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode array detectors (DAD) ; Toxicology ; Automated solute identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The possibilities and limitation of automated solute identification via UV/VIS spectroscopy in HPLC are demonstrated and applications in toxicologic analysis are described. A standard isocratic system is used. The influence of various chromatographic parameters on retention time is shown. A retention time window of ±15% is required. In addition to retention time, derived spectral data are calculated (minima and maxima of derivatives, area counts under standardized spectral ranges, absorption at various wavelength) and used for positive solute identification. It is possible to identify solutes with a high degree of certainty in urine and plasma if their concentration is at least 10 ppm.
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    A chromatographic analysis of hindered diffusion of saccharides in silica gels (1989)
    Springer
    Chromatographia 28 (1989), S. 370-374 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diffusion coefficients ; Distribution coefficients ; Dextran
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic technique as a means for experimental studies of diffusion in porous solids has been demonstrated. In this paper we report the effective diffusion coefficients which we have chromatographically obtained for two dextran samples and three low molecular weight solutes. The chromatographic method of measuring diffusional resistances in porous solids has the advantages of rapidity and simplicity. This method also provides information on the axial dispersion and distribution of a solute between the moving phase and the solvent held stationary in the pore. The elution curves of a packed column in pulse response experiments were analyzed by the method of moments to give the parameters of interest. The results indicate that pore diffusion of the solutes was appreciably restricted in comparison with diffusion in bulk solution. The degree of hindrance depended on the size of the diffusing substances.
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    The effects of buffer salt concentration on the HPLC retention of nucleic acid components (1989)
    Springer
    Chromatographia 28 (1989), S. 493-496 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nucleic acid components ; Buffer salt concentration ; Variation of retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In the reversed-phase high-performance liquid chromatographic studies of nucleotides, nucleosides and bases, phosphate and acetate are commonly used as buffer materials. The concentration of these buffer salts in the mobile phase exerts noticeable influence both upon the retardation and upon the separation of the nucleic acid components. This can be of certain usage in the fine adjustment of the elution order of individual components. The possible reasons for the observed data are discussed.
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    Separation of metal acetylacetonates by reversed-phase high-performance liquid chromatography (1989)
    Springer
    Chromatographia 28 (1989), S. 519-522 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase chromatography ; Separation of metal acetylacetonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using reversed-phase high-performance liquid chromatography acetylacetonate complexes with trivalent metals such as Al(III), Co(III), Cr(III) and Fe(III) have been examined in columns containing RP-2, RP-8 and RP-18 bonded phases. The mobile phase consisted of acetonitrile/water or methanol/water mixtures with various compositions. As shown the order of elution of the acetylacetonates depends on the type of the column packing and on the nature and concentration of the organic modifier in the mobile phase.
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    Ultrastructure of the nitrogen-fixing, filamentous, nonheterocystous cyanobacterium,Plectonema boryanum (1989)
    Springer
    Protoplasma 152 (1989), S. 130-135 
    Details
    ISSN: 1615-6102
    Keywords: Plectonema boryanum ; Cyanobacteria ; Ultrastructure ; Nitrogen fixation ; Nitrogen starvation ; Immunogold localization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of fructose-supplemented and unsupplemented nitrogen-fixing (fix +) and nonfixing (fix −)Plectonema boryanum UTEX 581 cells was examined by transmission electron microscopy. The most prominent structural differences included the arrangement and morphology of the thylakoids and alterations in the appearance of the interthylakoidal spaces. These ultrastructural differences, together with other observations such as glycogen content and presence of nitrogenase (using acetylene reduction assay and immunogold localization), readily distinguished nonfixingP. boryanum from nitrogen-fixing cells.
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    Characterization and nucleotide sequence of a novel gene fixW upstream of the fixABC operon in Rhizobium leguminosarum (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 536-544 
    Details
    ISSN: 1617-4623
    Keywords: Rhizobium leguminosarum ; Nitrogen fixation ; nif/fix genes ; Escherichia coli minicells ; Transcription regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary On the Rhizobium leguminosarum PRE sym plasmid, fixABC and a novel gene fixW were identified upstream of the regulatory gene nifA. The molecular masses of FixABC, 29, 44 and 50 kDa respectively, were estimated by polyacrylamide gel electrophoresis (PAGE) and of FixW, 25 kDa, by PAGE and nucleotide sequencing. Hybridization studies using bacteroid mRNA as a probe showed that fixABC is one operon which can be transcribed independently of fixW. Nucleotide sequencing revealed that both fixW and fixA are preceded by a nif consensus promoter. The fixA promoter partly overlaps the 3′-terminal coding region of fixW, indicating that readthrough from fixW into fixA is possible. Two open reading frames, ORF71 and ORF79, precede fixW and form one operon with fixW. ORF71 contains sequences homologous to the fixA promoter and 5′-terminal coding region. One more duplication of fixA sequences was detected, also located within the sym plasmid nif/fix clusters. One duplication of fixW sequences was found. No fixW homologue could be found in other nitrogen fixing organisms except in a number of R. leguminosarum strains.
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    URL: http://dx.doi.org/10.1007/BF00332421
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    Purification of human chorionic gonadotropin hormone by anion-exchange high-performance liquid chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 601-604 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange separation ; Preparative separations ; Human chorionic gonadotropin hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatography (HPLC) method was developed for the purification of 50mg crude human chorionic gonadotropin (HCG) hormone sample in one chromatographic run on a 250×10 mm SERVA DEAE Poliol-Si-500 column. During the 60-minute linear gradient of 0.05 M sodium sulfate, 0.05 M sodium hydrogen sulfate and 0.05% (v/v) acetonitrile in buffer “B” complete separation was accomplished in 40 min. Identity and purity of the fractions were checked by SDS electrophoretic method. The eluted HCG fractions were dialyzed for 24 hours to remove the buffer salts and liophilized. The activity of the hormone did not decreased significantly during the purification procedure.
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    Physico-chemical applications of HPLC (1989)
    Springer
    Chromatographia 27 (1989), S. 633-638 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adsorption isotherms ; Equilibria criteria ; Silica and carbon adsorbents ; Aromatic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Examples of high-performance liquid chromatography (HPLC) are given for the determination of adsorption equilibrium and distribution coefficients, calculation of excess adsorption isotherms from solutions ranging from 10−7 to 10−1 mole fraction, changes in activity coefficient of the component predominantly adsorbed from solution and substitution enthalpy. These examples stem from studies of HPLC and the static adsorption of benzene, anisole and benzaldehyde from solutions in n-heptane on macroporous silica and active carbon at various temperatures. A criterion is suggested for evaluating equilibrium in the HPLC process. The potential of size-exclusion chromatography (SEC) for evaluating the volume and predominant diameter of adsorbed pores as well as pore diffraction are discussed. Prospects for HPLC application to molecularstructural analysis and other purposes are discussed briefly.
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    The use of large polycyclic aromatic hydrocarbons to study retention in non-aqueous reversed-phase HPLC (1989)
    Springer
    Chromatographia 27 (1989), S. 118-122 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase chromatography ; Non-aqueous reversed-phase chromatography ; Polycyclic aromatic hydrocarbons ; Solvent strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Elution strengths of 11 common HPLC solvents on a polymeric C18 phase were compared using a marker set of polycyclic aromatic hydrocarbons. Naphthalene, pyrene, benzo[ghi]perylene, and three larger naphthologues of 8, 10, and 12 rings (constituting a “naphthalene zigzag” series) were chosen because they span the solvent strength range up to and including the strongest solvents, tetrahydrofuran (THF) and chlorobenzene. Four pairs of similarly shaped isomers were used to probe solvent selectivity. With the exception of THF, HPLC solvent strength correlated with observed red shifts of fluorescence band maxima in each solvent. For THF, the pure solvent and blended mixtures behaved quite differently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265862
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  • 93
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    HPLC determination of catabolic amines in silage using their dansyl derivatives and an electrochemical detector (1989)
    Springer
    Chromatographia 27 (1989), S. 216-220 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detector ; Amines ; Silages ; Feedstuffs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of the electrochemical detector (EC) in the high performance liquid chromatography (HPLC) of dansyl derivatives of biogenic amines is reported. Isocratic and gradient elution patterns of synthetic mixtures of putrescine, cadaverine, 1,6-diaminohexane, tryptamine, histamine, tyramine, spermine and spermidine on a reversed phase column are shown. Hydrodynamic voltammograms of standard compounds are presented. The detection limits of the EC are compared with those of ultraviolet and spectrofluorimetric detectors. A chromatographic profile of amines from the proteolytic catabolism of maize silage byClostridia is shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260449
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  • 94
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    Equilibrium structures of the Arg-aldehyde moiety upon HPLC of peptides (1989)
    Springer
    Chromatographia 27 (1989), S. 228-232 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase ; 13C n.m.r. ; Arginine-aldehyde peptides ; GYKI-14166
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic and13C n.m.r. spectrometry methods were used for the investigation of peptides containing arginine-aldehyde moiety. Investigation of a model compound, N-benzoyl-Arg-H, showed that in an acidic mobile phase peptides containing the arginine-aldehyde group elute in three characteristic peaks. The components of the peaks were found to be constituents of an equilibrium mixture. The structures of the two components were identified, one as the aldehyde hydrate, the other as the cyclanol derivative. The reactivity of TRIS (HCl) buffer at pH 8.5 with the arginine aldehyde moiety was used for the assignment of the equilibrium structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260452
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  • 95
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    Ion-pair reversed phase HPLC determination of nucleotides, nucleosides and nucleobases — Application to nucleotide metabolism in hepatocytes (1989)
    Springer
    Chromatographia 27 (1989), S. 639-643 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase ; Ion-pair ; Recoveries ; Hepatocytes ; Purine compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three groups of metabolites were analyzed in extracts of rat hepatocytes by an HPLC method: (i) nucleotides (ATP, ADP, AMP, GTP, GDP, UTP, UDP, IMP, UMP), (ii) nucleosides and nucleobases (adenosine, adenine, guanosine, inosine, xanthine, hypoxanthine, uridine) and (iii) inhibitors of xanthine oxidoreductase (oxypurinol, allopurinol). Perchloric acid extracts were neutralized with K2CO3/triethanolamine and analyzed at 254 nm by reversed-phase ion-pair high-performance liquid chromatography. The nucleotides and their derivatives were separated with a gradient elution using 10 mM NH4H2PO4/2 mM t-butylammonium-phosphate and acetonitrile. Recovery values were estimated for the extraction procedure used. The method was applied to the investigation of nucleotide metabolism of hepatocytes of starved rats at anoxia and reoxygenation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02258995
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  • 96
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    High-performance liquid chromatographic determination of (−)-cathinone in plasma (1989)
    Springer
    Chromatographia 27 (1989), S. 201-204 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cathinone metabolites ; Plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatography (HPLC) for the determination of (−)-cathinone in rabbit and human plasma has been studied. The problem of dimerization during extraction from plasma was satisfactorily resolved. Detection was by UV at 257 nm. Concentration levels as low as 24 ng ml−1 were satisfactorily determined. This level of sensitivity should be adequate for the detection of (−)-cathinone in the blood of khat users and also for the quantitative determination of (−)-cathinone in blood for pharmacokinetic purposes. The applicability of the assay procedure to pharmacokinetic studies is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260446
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  • 97
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    A HPLC method for specific determination ofα-amylase and glucoamylase in complex enzymatic preparations (1989)
    Springer
    Chromatographia 27 (1989), S. 328-332 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Glucose, maltose and maltotriose ; α-Amylase and glucoamylase ; Microfungal cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In the hydrolysis of soluble starch by mixtures of α-amylase and glucoamylase, the ratios maltose/glucose and maltoriose/glucose linearly depend, over a wide range, on the relation between both enzymes and are independent on the activity level of the enzymatic preparation. HPLC determination of hydrolysis products (glucose, maltose and maltotriose) of soluble starch by mixtures of these enzymes, after incubation under controlled conditions, is a rapid method for the evaluation of the relative levels of each enzyme in the mixtures. The method, first developed using pure commercial amylases, is applied, with consistent results, to cell free media ofAspergillus niger cultures on a glycogen-rich effluent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321279
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  • 98
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    A study of the practical limitations of principal components analysis and the labelling of unresolved HPLC peaks (1989)
    Springer
    Chromatographia 27 (1989), S. 343-358 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Principal components analysis (PCA) ; Iterative target transformation factor analysis (ITTFA) ; Peak labelling ; Chromatographic peak deconvolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The method of iterative target transformation factor analysis (ITTFA) used in conjunction with second derivative peak finding has shown to be a practical method for the peak deconvolution and reconstruction of HPLC chromatograms and spectra. The second derivative method of peak finding is acceptable for resolutions above 0.5 for peaks of similar heights. Above 0.5 resolution the labelling gives correct results where the spectra are substantially different and also when reasonably similar. Below this value the peak labelling was still accurate where the spectra were different. Solvent effects on the spectra of the compounds studied are small and do not hinder the peak labelling process. Thus small “local” libraries are feasible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321282
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  • 99
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    Separation and determination of nitrite ion by affinity chromatography with cyano(pheophytinato a)cobalt(III) charged column (1989)
    Springer
    Chromatographia 27 (1989), S. 461-464 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorophyll-bonded stationary phase ; Cyano(pheophytinato a)cobalt(III) ; Pheophytin a
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation and determination of the nitrite ion by affinity chromatography is described. The good separation of the nitrite ion was obtained by using cyano-(pheophytinato a)cobalt(III) bonded octadecylsilica as the stationary phase and water of pH 4.3 adjusted by acetic acid as the mobile phase. Conventional ion chromatograph was also used for the analysis of the nitrite ion. For the synthetic samples prepared by mixing the nitrite and nitrate ions, analytical values obtained by affinity chromatography were in agreement with calculated values and close to the analytical values obtained by ion chromatography. In the proposed affinity chromatography, the nitrite and nitrate ions could be determined in the concentration range of 0.15–1.0ppm and 0.1–1.0ppm with relative standard deviations (n=10) of 5.3% and 4.7%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02319564
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  • 100
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    Size exclusion chromatography on porous fractals (1989)
    Springer
    Chromatographia 27 (1989), S. 257-263 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion ; Fractal dimension ; Retention model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Some porous packings used in chromatography have been claimed to be fractals with a scale of sizes a〈l〈L, where a is a molecular size and L is the size of the largest pores. For a fractal porous packing, the excluded volume for molecules in solution in the vicinity of the packing surface is directly related to Df, the fractal dimension of the pore surface (2〈Df〈3). Since retention in size exclusion chromatography is itself directly related to this excluded volume, the fractal nature of the packing provides a model of retention in this technique. According to this model there is a linear relationship between log Rs and log(1-Kd), where Rs is the hydrodynamic radius of the solute macromolecules and Kd the distribution coefficient. The fractal dimension is derived from the slope of this plot. Size exclusion chromatographic retention data have been analyzed according to the model. It is found that some HPLC packings are fractals with fractal dimensions ranging from about 2.15 to 2.6, depending on the material. Such a large range of Df values indicates large variations in the selectivities and domains of applications of the different packings. For some classical gel filtration chromatographic gels, the fractal retention model does not seem to apply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260458
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