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  • 1
    Electronic Resource
    Electronic Resource
    Enriching volatile compounds by a temperature gradient tube (1973)
    s.l. : American Chemical Society
    Analytical chemistry 45 (1973), S. 965-967 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60328a045
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of an echinocandin B-producing strain blocked for sterigmatocystin biosynthesis reveals a translocation in the stcW gene of the aflatoxin biosynthetic pathway (2000)
    Springer
    Journal of industrial microbiology and biotechnology 25 (2000), S. 333-341 
    Details
    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
    URL: http://dx.doi.org/10.1038/sj.jim.7000076
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Discovery of utmost inner time precision in chromatography (1997)
    Springer
    Fresenius' journal of analytical chemistry 359 (1997), S. 208-212 
    Details
    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
    URL: http://dx.doi.org/10.1007/s002160050562
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  • 4
    Electronic Resource
    Electronic Resource
    Iterative Berechnung der Totzeit aus Bruttoretentionsdaten (1974)
    Springer
    Chromatographia 7 (1974), S. 696-697 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An iterative method for computing gas hold-up time of the GC-system used from known retention indices and non-adjusted retention times of three substances is described. The algorithms used and a program for the Hewlett Packard hp 65 pocket calculator are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269200
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  • 5
    Electronic Resource
    Electronic Resource
    Gas-Chromatographie in der Umweltanalytik. Teil 1 (1972)
    Springer
    Chromatographia 5 (1972), S. 281-283 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02270608
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  • 6
    Electronic Resource
    Electronic Resource
    Rechnerhilfe in der gas-chromatographie I. Präzise Retentionsindices aus Bruttoretentionszeiten (1974)
    Springer
    Chromatographia 7 (1974), S. 251-257 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Leistungsfähige Kleinstcomputer, wie der kürzlich auf den Markt gekommene und derzeit einzige frei programmierbare Taschencomputer HP-65 erlauben neue Auswertetechniken in der qualitativen Gas-Chromatographie. Durch Berechnung der Totzeit aus drei beliebigen in ihrem Retentionsindex bekannten durch ihre Bruttoretentionszeit erfaßbaren Hilfssubstanzen läßt sich mit einem Rechenzeitaufwand von jeweils 4 Sekunden der Retentionsindex beliebiger Stoffe aus den zugehörigen Bruttoretentionszeiten berechnen. Dabei dienen jeweils zwei wiederum beliebige Stoffe, die den zu berechnenden Stoff x „einschließen”, als Bezugssubstanzen. Somit ist es nicht mehr notwendig, stets n-Alkane als Bezugsstoffe zu verwenden, jedoch müssen die Retentionsindices der Ersatzbezugsstoffe trotzdem einmal gegen Kohlenwasserstoffe ermittelt worden sein. Somit bleibt das n-Alkan Grundbezugssubstanz. Die neuen jedem Labor zugänglichen mathematischen Hilfsmittel machen die Anwendung des so aussagekräftigen Retentionsindex nach Kovats auch z. B. bei der Pestizidanalytik möglich, wo man wegen der Unempfindlichkeit des ECD gegenüber Kohlenwasserstoffen und Methan die in anderen Bereichen der GC-Analytik bereits unersetzliche qualitative Auswertung praktisch noch nicht kennt. Durch lineare Regression nach einer bewußten „Zwangslinearisierung” lassen sich die Daten weiter wesentlich verbessem. Die zugehörigen HP-65 Programme werden mit allen Einzelheiten beschrieben, so daß man sie unmittelbar auf eigene Rechner übertragen kann. Die Rechenkosten betragen rund 10−2 Pfennig pro Sekunde.
    Notes: Summary Today, mini computers (e. g., HP-65) are available in a pocket version. They can be programed quickly, simply and very effectively. Thus, mathematical algorithm can be used for retention index calculations from nonadjusted retention time data using an iteration. Although sometimes the true data of retention index, as a function of the adjusted retention time, are non linear, it can be shown that linearization of this function — together with linear regression — is of great practical value. Another improvements are achieved by using nonalcanes as an inner standard in qualitative routine analysis of medium to high polar compounds, as well as by using the retention index as the address for correction factors for quantitative analysis and as the command to start any type of program in gas chromatography, e. g., temperature programs, column switching programs, detector switching programs, and all switching programs in preparative gas chromatography. This is true because retention index data are in minimum by a factor of ten more precise than other measure in qualitative gas chromatography. Algorithms used and programs for the HP-65 pocket computer are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321776
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Problems and solutions to measure and maintain the high separation power of capillary columns (open tubular and packed type) at their optimum (1975)
    Springer
    Chromatographia 8 (1975), S. 491-498 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation number, TZ, is a practical measure of separation quality. TZ strongly depends on k. Sum of all TZ over the whole k-range divided by the uncorrected retention time tms of the last peak is a good measure of the separation power. The combined use of TZ and retention index data combines selectivity and separation quality in a simple and clear way. The aualitative range of a capillary column, open tubular or micro-packed, is at best expressed by the retention index range at the column temperature and is strongly dependent on the time of analysis. The acceptable temperature range of a capillary column, from far subambient to the acceptable upper limit can be simply expressed by computed data as well as the defined qualitative range. For the precalculation of both simple pocket computer programs are presented. The ‘four inlet-outlet-concept’ of gas chromatography columns (including capillaries) is discussed briefly; it offers new possibilities for analytical as well as quality check purposes, including accurate measurements of split ratios and flow rates; the tightness of the system under real life conditions can be measured by integrator, by on-line data acquisition systems as well as by hand. Sample transfer lines can simply be made as inactive as the most inactive glass capillary. This is important if we want to use the capillaries in our environment as instrument for quantitative analysis from 100 to 10−10% concentration by split or splitless injection and by capillary enrichment. Quantitative backflush and quantitative hinflush [8] or other new possibilities for capillaries, run in the four-inlet-outlet-mode, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267590
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Trenncassetten zur Gas-Chromatographie Ein neues technisches System zur Erleichterung normaler und extrem schwieriger Analysen, besonders in der Umwelt-Analytik (1974)
    Springer
    Chromatographia 7 (1974), S. 688-695 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden Prinzip, Eigenschaften und Anwendungsbeispiele der Trencassette zur Gas-Chromatographie, besonders unter den Aspekten der Spurenanalytik beschrieben. Die Trenncassette erlaubt totvolumenfreie on-column-Anreicherungen außerhalb des Gas-Chromatographen, sekundenschnellen werkzeugfreien Einbau in einen mit dem Cassetteninterface versehenen (beliebigen) GC-Apparat, beliebigen Säulenaustausch,-Kopplung, zweidimensionale Trennung, quantitativen backflush und wegen des technischen sehr einfachen Konzepts zahlreiche weitere Schalt- und Anwendungsmöglichkeiten. Trenncassetten sind, sofern das Säulenmaterial dies aushält, von −160°C bis +350°C gasdicht bis 22·106 Pa Stickstoff (RT) und können vom ersten bis zum letzten Millimeter aus Stahl, Nickel, Glas, Quarz sein. Ihr Einbau in GC-Geräte kann bei entsprechender Gerätekonzeption völlig ohne Leitungen erfolgen. Es kann in die Cassette dosiert und direkt in den oder die Detektoren eluiert werden, wobei gepackte Säulen genauso wie z.B. Hochleistungsglaskapillaren oder mikrogepackte Glassäulen angewendet werden können. Die GC-Trenncassette ist der Vorläufer für die HPLC-Trenncassette.
    Notes: Summary The principle and use of separation cassettes in gas chromatography with particular emphasis on aspects of environmental trace analysis is described. The separation cassette provides on column enrichment and a dead-volume-free connection external to the gc and provides a very rapid connection, without need of a tool, to a gc with a cassette interface. Owing to its versatility the separation cassette makes possible the solution to many analytical problems and the use of techniques such as column exchange, column coupling, two dimensional separation and quantitative backflush. Cassettes are gas-tight to 22·106 Pa nitrogen and, provided the column packing is sufficiently stable, the locking system operates between −160°C and +350°C without change. Cassettes can be made completely from stainless steel, nickel or fused quartz. Insertion into special gas chromatographs can be made without gas tubing, hence the sample is injected into the cassette and effluent from it fed directly to the detector. Packed columns or micropacked glass columns as well as capillaries may be used. The gc-cassette is the precursor of the hplc-cassette.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269199
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Letters to the editors (1976)
    Springer
    Chromatographia 9 (1976), S. 643-646 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290539
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    The editorial board of chromatographia offers financial aid to young scientists for participation in certain international symposia (1976)
    Springer
    Chromatographia 9 (1976), S. 55-55 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269218
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    Paper (German National Licenses)
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