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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 45 (1973), S. 965-967 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 359 (1997), S. 208-212 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An up to now unknown high “inner time precision” in isocratic gas chromatography (GC) and high pressure column liquid chromatography (HPLC) has been realized using quartz clock driven A/D converters and special statistically evaluating integration software. This millisecond level inner time precision is detectable by two very linear data correlations: a) the log of adjusted retention times (log(t R′)) versus the molecular weight of separated members of homologues and b) the peak width at half height versus correct k-values of the homologues. The inner time precision at the millisecond level is not lost by slight errors (up to seconds) in the starting times of GC or HPLC determinations. The correlation coefficient of the two linear data correlations allows a thorough analysis of instrument quality. The highly linear correlation of peak width and k in a wide range of mobile phase speeds is in disagreement with theoretical models of chromatography. Especially the rule of variance additivity is not valid in isocratic elution chromatography.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1476-5535
    Keywords: Keywords: Aspergillus nidulans; aflatoxin; sterigmatocystin; mutagenesis; translocation; echinocandin B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Echinocandin B (ECB), a lipopolypeptide used as a starting material for chemical manufacture of the anti-Candida agent LY303366, is produced by fermentation using a strain of Aspergillus nidulans. In addition to ECB, the wild-type strain also produces a significant level of sterigmatocystin (ST), a potent carcinogen structurally related to the aflatoxins. Characterization of a mutant designated A42355-OC-1 (OC-1), which is blocked in ST biosynthesis, was the result of a chromosomal translocation. The chromosomal regions containing the breakpoints of the translocation were isolated and DNA sequencing and PCR analysis of the chromosomal breakpoints demonstrated the translocation occurred within the stcW gene of the ST biosynthetic pathway, resulting in disruption of the open reading frame for this gene. Biochemical feeding studies indicate the involvement of this gene product in the conversion of averufin to 1-hydroxy versicolorone. This work demonstrates an effective synergy between classical strain improvement methods and molecular genetics. Journal of Industrial Microbiology & Biotechnology (2000) 25, 333–341.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 83-87 
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Electroosmosis ; Electrochromatography ; Electric field ; Planar chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Planar electrochromatographic separations of test substances were performed on non pre-wetted, commercially available, thin-layer plates. The behavior of different layers and solvents was studied in an applied electric field of up to 2000 V cm−1. Evident electrokinetic effects, electroosmosis and electrophoresis were observed only on silica gel and polyamide layers developed with polar solvents. The selectivity of separation of nonionic and ionogenic compounds was greatly enhanced. Although experimental conditions were controlled to a certain extent, results obtained with the same solvents were reproducible within 5%.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 5 (1972), S. 281-283 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The quantitative limitations of environmental analysis by gas chromatography can be shown simply by means of a formula (1) that suggests that enrichment prior to sampling is essential. Ethylene, a most reactive hormone for plants, is taken as an example to shown the possibilities of selective separation as well as selective detection after enrichment in a so-called “Gradientenrohr”-technique. This first part of a series of short communications will be continued later to inform users of gas chromatography of the power of the method for specific environmental analysis by combined enrichment, separation and detection, under selective or specific conditions, as the number of traces in every type of sample is enormous. By this procedure active compounds in air as well as water, body fluids, solid materials and each stage between solid and liquid can be sampled, enriched, separated and detected.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 12 (1979), S. 338-344 
    ISSN: 1612-1112
    Keywords: High-performance liquid column chromatography ; High-performance thin-layer chromatography ; Comparison for automation ; Optimization ; Concept to measure qualification of the techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ohne vorherige Optimierung darf eine analytische Methode nicht automatisiert werden. Ein theoretisches und praktisches Konzept, nach welchem HPLC bezüglich Trennleistung und Trennvermögen optimiert werden kann, wird gegeben. Es zeigt, daß klassische Kennzahlen wie die Zahl theoretischer Trennstufen oder Bodenhöhenwerte außerstande sind, den tatsächlichen Leistungsstand einer chromatographischen Methode sachgerecht zu beurteilen. Das “abt-Konzept” hingegen beschreibt Stand und Trend bei der Optimierung perfekt. Hochleistungs-Dünnschicht-Chromatographie wird man wegen ihrer so schon extremen Probenkapazität—im schnellsten Falle derzeit 24 Proben in 30 Sekunden getrennt-nicht vollautomatisieren können. Dennoch werden beide Methoden bezüglich Automatisierung verglichen.
    Notes: Summary Automation of an analytical technique can be accepted only when the whole procedure can be optimized. Examples amples are given how to optimize HPLC, and how misleading the classical data of theoretical plate height or plate numbers are. It is shown, how well the “abt concept” helps to optimize HPLC and to understand the results. HPTLC is too powerful for full automation due to its large sample throughput at an analytical separation speed of 24 samples in 30 seconds. HPLC and HPTLC are compared with respect to full or partial automation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 9 (1976), S. 643-646 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 9 (1976), S. 463-467 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden die Grundlagen eines offensichtlich allgemeingültigen Bewertungsverfahrens in der Gas- und Flüssig-Chromatographie (GC, HPLC, DC, HPDC) vorgestellt und die Schlußfolgerungen für die Praxis diskutiert. Das Bewertungsverfahren ist einfach, es zeigt aber den ganz außerordentlich wichtigen Einfluß instrumenteller und methodischer Feinheiten (unterschiedliche Optimierung, schärfste Startkonzentration vor Trennbeginn der zu trennenden Stoffe) auf, welche Voraussetzung sind für hohe Trennleistungen und ein hohes Trennvermögen in allen chromatographischen Techniken. Das Bewertungsverfahren erlaubt einen ehrlichen praxisgerechten Methodenvergleich und dient damit der Optimierung experimenteller Arbeit.
    Notes: Summary The basis of a procedure to measure, calculate and discuss true separation-quality indices is given and discussed. The procedure is simple and shows the most important role of components of the instrument and the technique used—optimization for different conditions, highest injection concentration per inlet volume prior to start of a separation—which are responsible for high separating efficiency and high separating power in all chromatographic techniques. The procedure allows a true comparison of separation methods and helps in the optimization of experimental work. This paper is a supplment to the green pages in Chromatographia9, 335 (1976) (German version) which will appear in English in a forthcoming issue.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 91-92 
    ISSN: 0935-6304
    Keywords: Data evaluation, peak width measurements in GC, LC, TLC ; Peaks are in principle non symmetric, non Gaussian shaped ; Standard deviation and variance cannot be measured directly as usual ; Systematic error easily larger than 50% ; Calculation of correct standard deviation/variance presented ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 164-168 
    ISSN: 0935-6304
    Keywords: Thin Layer Chromatography, HPTLC ; Fastest possible analytical mode: Anticircular separation ; First principal analytical details ; Most economical TLC/HPTLC technique, quantitative comparison with linear and circular mode ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principal analytical details for the third of three possible modes in high performance thin-layer chromatography are given, namely the anticircular mode. Separation is achieved by allowing the mobile phase to enter the plate layer on a precise outer circle line, from where it flows towards the centre with nearly constant speed. This technique is theoretically and practically the fastest of all three possible in HPTLC. It permits maximum sample capacity with a minimum of time, layer and mobile phase consumption. It is therefore the most economical HPTLC technique.A new carrier-free mobile phase transfer principle is used. The conditions for qualitative and quantitative analysis are good: repeatability, reproducibility and accuracy of routine TLC analyses are superior to those achieved by the classical trough technique. The specially narrow spot-path in anticircular HPTLC facilitates automated quantitation. Compared with the linear and circular modes, the anticircular mode shows better separation and significantly increased sensitivity at higher Rf-values. The drawback, however, is that the separation power (expressed by the separation number) is lower compared with the other two modes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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