ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Sample size and retention values in gradient liquid chromatography of synthetic polymers (1996)
    Springer
    Chromatographia 42 (1996), S. 185-190 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gradient elution of synthetic polymers ; Polystyrene and various styrene copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention times in gradient liquid chromatography of synthetic polymers are often dependent on sample size. They increase with column load if the separation mechanism is governed by a solution process but decrease with increasing load if the mechanism is governed by adsorption. Since retention times independent of sample size are a prerequisite for peak identification as well as for the correct measurement of elution bands of samples with a broad distribution, measures to counteract sample-size effects deserve attention. Usually both solubility and adsorption are effective in gradient liquid chromatography of synthetic polymers. An appropriate balance of both effects is suitable for diminishing the influence of sample size on retention time of synthetic polymers. Ternary gradients allowing independent control of solubility and adsorption are promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269651
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high-performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 557-563 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/methyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and methyl methacrylate (MMA) were separated by both normal and reversedphase gradient chromatography. Both modes could be performed by sudden-transition gradients where the polymers were injected into a non-solvent whose polarity was either rather low (e.g.,n-heptane) or high (e.g., acetonitrile). Then the solvent strength of the starting eluent was rapidly increased to a given level by addition of dichloromethane. Under properly defined conditions, the sample components still remained on the column. Elution could be triggered off by the steady addition of another non-solvent whose polarity was opposite of that of the starting non-solvent. Thus, the mixture of five copolymers with MMA content ranging from 14 to 84% could be separated on a polar cyanopropyl column by injection inton-heptane and elution through acetonitrile (normal phase mode) and on a RP C18 column by injection into acetonitrile and elution throughn-heptane (reversed-phase mode), provided that in both modes about 30% dichloromethane was added to the starting non-solvent. The elution sequence in the reversed-phase mode was opposite to that in the normal-phase mode, obeying the approved polarity rules of chromatography in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268279
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 4. Sudden-transition gradient elution of styrene/ethyl methacrylate copolymers in reversed phase mode (1994)
    Springer
    Chromatographia 39 (1994), S. 170-174 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/ethyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and ethyl methacrylate have been separated according to composition byn-heptane gradients on a C18 bonded phase after injection into acetonitrile and subsequent sudden transition to a concentration of either dichloromethane or tetrahydrofuran between 30 and 50% or 20 and 50%, respectively. Acetonitrile is a polar non-solvent for the copolymers under investigation and ensures proper retention of the samples on a non-polar stationary phase. Dichloromethane and tetrahydrofuran are good solvents of moderate polarity. The addition of, e.g., 30 vol% of one of these solvents increased the dissolution power of the starting eluent but not to the extent necessary for elution. The latter was achieved by the addition ofn-heptane, which is a non-solvent for the polymers investigated. Thus, its eluting power must be understood as the consequence of its modifying effect on the polarity of the eluent mixture. The higher the content of copolymer in ethyl methacrylate the earlier it was eluted. Since acetonitrile andn-heptane are only partly miscible, phase diagrams were measured after the addition of either tetrahydrofuran or dichloromethane as a third component. Homogeneous mixtures were obtained on addition of about 30% solvent (one of both of the latter).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274496
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Non-LTR retrotransposons with unique integration preferences downstream of Dictyostelium discoideum tRNA genes (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 772-780 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsDictyostelium ; tRNA gene ; Retrotransposon ; Genome evolution ; Dictyostelium Genome Project
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Retrotransposable elements are genetic entities which move and replicate within host cell genomes. We have previously reported on the structures and genomic distributions of two non-long terminal repeat (non-LTR) retrotransposons, DRE and Tdd-3, in the eukaryotic microorganism Dictyostelium discoideum. DRE elements are found inserted upstream, and Tdd-3 elements downstream, of transfer RNA (tRNA) genes with remarkable position and orientation specificities. The data set currently available from the Dictyostelium Genome Project led to the characterisation of two repetitive DNA elements which are related to the D. discoideum non-LTR retrotransposon Tdd-3 in both their structural properties and genomic distributions. It appears from our data that in the D. discoideum genome tRNA genes are major targets for the insertion of mobilised non-LTR retrotransposons. This may be interpreted as the consequence of a process of coevolution, allowing a viable population of retroelements to transpose without being deleterious to the small microbial host genome which carries only short intergenic DNA sequences. A new nomenclature is introduced to designate all tRNA gene-targeted non-LTR retrotransposons (TREs) in the D. discoideum genome. TREs inserted 5′ and 3′ of tRNA genes are named TRE5 and TRE3, respectively. According to this nomenclature DRE and Tdd-3 are renamed TRE5-A and TRE3-A, respectively. The new retroelements described in this study are named TRE3-B (formerly RED) and TRE3-C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380051140
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The genome of the social amoeba Dictyostelium discoideum (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 435 (2005), S. 43-57 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03481
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Über die Löslichkeit von PVC in Weichmachern (1973)
    Springer
    Colloid & polymer science 251 (1973), S. 5-16 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Mittels der mikroskopischen Untersuchungsmethode wird die Lösetemperatur von PVC in Dioctylphthalat in Abhängigkeit vom Molekulargewicht und der Vorbehandlung der Proben bestimmt. Bei technischen Produkten wird ein Anstieg der Lösetemperatur mit dem Molekulargewicht gefunden, wobei das Suspensions-polymerisat eine höhere Lösetemperatur zeigt, als dem Molekulargewicht entsprechen würde. Umfällen der technischen Produkte verwischt diesen Unterschied sowie den Einfluß des Molekulargewichtes. An Fraktionen wird ein Minimum der Lösetemperatur bei mittleren Molekulargewichten gefunden. Maßnahmen, die bei kristallisierenden Polymeren die Kristallinität erhöhen (Tempern, Quellungskristallisation), führen zum Ansteigen der Lösetemperaturen. Die gewonnenen Ergebnisse werden mit der Annahme gedeutet, daß neben dem Molekulargewicht auch der Ordnungsgrad von entscheidendem Einfluß auf die Höhe der Auflösungstemperatur von PVC in Weichmachern ist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01501414
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    A. K. Bledzki, T. Spychaj: Molekulargewichtsbestimmung von hochmolekularen Stoffen. D. Braun (Hrsg.).154 S., 37 Abb., 18 Tab., 24 × 17cm. Hüthig & Wepf, Basel - Heidelberg - New York 1991. Übungsaufgaben zur Chemie und Physik der Polymere Kartoniert. Preis: 38, - DM (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 193-193 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340220
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Separation of copoly(styrene/acrylonitrile) samples according to composition under reversed phase conditions (1991)
    Springer
    Chromatographia 32 (1991), S. 107-112 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Styrene/acrylonitrile polymers ; Gradient elution ; Solubility effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copoly(styrene/acrylonitrile) samples (S/AN) have been repeatedly separated according to composition by gradient HPLC with alkane hydrocarbons as a starting eluent A and dichloromethane (DCM) or tetrahydrofuran (THF) as a solvent B. In these systems, retention increased with AN content of the copolymers. The chemical nature of the column packings used had almost no influence on the retention of S/AN samples. The present paper shows thatn-pentane andn-heptane, when used in a given volumetric gradient with DCM+20% methanol as a solvent B, lead to identical solution characteristics of S/AN on silica columns. A similar result was obtained on C18 columns withn-heptane or cyclohexane, whereas gradient elution with toluene as a starting eluent caused insufficient resolution. Reversed phase separation of S/AN copolymers could be achieved on polystyrene gel columns through gradients with methanol as a starting eluent and DCM or THF as a solvent B. In both systems, retention decreased with increasing AN content of the copolymers. The elution characteristics were almost linear in the range 0–20 wt% AN. This behaviour can be understood in the context of polymer solubility: in both systems, the solubility borderline of S/AN has a distinct maximum at about 25 wt% AN. Reversed phase separation was achieved at the lefthand slope of these curves where the dissolution of a sample with a higher AN content requires less DCM or THF solvent than the dissolution of copolymers which are poorer in AN. This idea predicts that samples with more than 25 wt% AN should elute later than S/AN whose composition is near to the solubility maximum. This indeed was found with a copolymer containing 36.2 wt% AN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325011
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268369
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high performance liquid chromatography 1. Principles of sudden transition gradients and elution characteristics of copolymers from styrene and methacrylates (1993)
    Springer
    Chromatographia 37 (1993), S. 7-12 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/methacrylates) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Proper retention of polymers in high performance liquid chromatography often requires injection into a starting eluent which is not a solvent for the sample under investigation. In this case, the polymer is precipitated at the top of the column. Subsequent gradient elution has to be performed by addition of an eluent with sufficient chromatographic strength and solvent power. In normal phase chromatography, it must be a solvent of high polarity. With the gradient elutions reported so far, polarity and dissolution power were simultaneously increased. The present paper reports the separate control of solvent strength and chromatographic power by applying gradient programs which include sudden addition of a moderately polar solvent. The amount of the latter does not suffice for elution, which is performed by subsequent, controlled addition of a highly polar nonsolvent. Sudden transition gradients of this kind work with, e.g.,iso-octane as a nonpolar starting eluent, tetrahydrofuran as a solvent of intermediate polarity, and methanol as a strongly polar nonsolvent. They have been applied to copolymers from styrene and ethyl methacrylate, methyl methacrylate, or methoxyethyl methacrylate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272180
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...