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  • Column liquid chromatography  (158)
  • Springer  (158)
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  • Springer  (158)
  • American Geophysical Union
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • Cambridge University Press
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 645-647 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Electrochemical detection ; Cysteinyldopamine ; Tyrosinase ; Autoxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary 5-S-Cysteinyldopamine, a new metabolite of dopamine, was determined in urine by high-performance liquid chromatography with electrochemical detection. The catechol was detected in 14 of 21 melanoma patients and 7 of 21 normal subjects; the highest values were 657 μg/day for melanoma patients and 44 μg/day for normal subjects. These results suggest that the cysteine conjugate may arise from autoxidation of dopamine but tyrosinase may also participate in the oxidation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 136-142 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chemical reaction detector ; Carbamate insecticides ; Quantitation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary For the determination of trace amounts of carbamate insecticides in vegetables the combination of liquid chromatography with post column chemical derivatization (chemical reaction detector) is used. In a two step reaction detector the carbamates are firstly saponified in 0.01 M sodium hydroxide at 80°C with a reaction time of 30sec. To this mixture OPA reagent is added to detect the methylamine generated in the saponification. Optimization strategies for this reaction are demonstrated. At a temperature of 80 °C a reaction time of 80 sec is sufficient for quantitative transformation of the methylamine. The peak dispersion can be reduced and hence the detection limit improved by decreasing the diameter of the tubes and by diminishing dilution through the addition of reagent. A 1∶24 ratio of reagent to column (reactor) effluent is possible with cyclone-type mixers. The quantitation of carbamates in different vegetables is demonstrated. The detection limit is 20ppb at a signal to noise ratio of 10∶1.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 205-213 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiral phases ; Optimization of separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The preparation and properties of chiral bonded phases with amino acid groups are described. These phases were used in non-polar eluents and in aqueous systems in the presence of Cu2+ ions in the ligand-exchange mode. The optimization of chiral resolution is demonstrated for both cases. With non-polar eluents similarity between bonded groups and solutes is required. The elution could be accelerated by non-protonic moderators. Ligand-exchange separation is influenced by the copper content of the eluent and the stationary phase, the organic moderator concentration, the pH and ionic strength of the buffer and by the temperature. Structural requirements of both the bonded groups and of the solutes for chiral separation are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reversed-phase capacity factors ; Cavity term ; Molar volumes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Reversed-phase liquid chromatographic capacity factors are well correlated by an equation of the form: $$logk' = (logk')_0 + mV/100 + s\pi ^* + b\beta + a\alpha $$ wheremV/100 measures the cavity term and π*, β, and α are the solvatochromic parameters that measure solute dipolarity/polarizability, hydrogen bond acceptor basicity, and hydrogen bond donor acidity respectively. Liquid molar volume (molecular weight divided by liquid density at 20°C) $$\bar V$$ , and computer-calculated intrinsic (van der Waals) molecular volume, $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ , are compared as measures of the cavity term in a number of correlations. $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ leads to more precise correlations as well as to a “cleaner” dissection of the multiple solute/solvent interactions. The opposing exoergic effect of solvent donor/solute acceptor hydrogen bonding, and endoergic cavity term are the main factors influencing HPLC capacity factors.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 40-42 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Pyridate ; CL-9673 ; Reversed phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The application of a simple reversed-phase, HPLC-UV method for the determination of the contact herbicide pyridate and its main metabolite 3-phenyl-4-hydroxy-6-chloropyridazine-known as CL-9673-in green cereals, grains and straw is described. The method is based on a simple extraction, separation of pyridate from its metabolite, hydrolysis of pyridate to CL-9673, high-performance liquid chromatographic separation of CL-9673 in both fractions using only one reversed phase column and UV-detection. The method is sensitive down to 3 ngg−1 CL-9673 in green plants and grain and 5ngg−1 in straw. In the range 0.05–1.0mgkg−1 recoveries are between 73.7% and 109% from green plants, between 77.7% and 102% from grains and between 77.3% and 87.5% from straw.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Betablocker drugs ; Lipophilicity ; Capacity factors ; Distribution coefficients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The reverse-phase, high-pressure liquid chromatographic capacity factors (k') of a series of 18 betablocking agents were determined in order to establish correlations with their distribution coefficient values (D), obtained from four bibliographic sources. Under the three pH conditions studied (3.5, 6.2 and 7.5) statistically significant linear correlations (p〈 0.002) between log k' and log D values were obtained for the four series studied. In this series it is concluded that the k' factor is a useful and reliable relative lipophilicity parameter.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 81-87 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Recycle chromatography ; Pressure dependence ; Capacity factor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary It was found experimentally that the potential for routine, rapid high-efficiency separations by alternate column, recycle, reversed-phase chromatography is limited by the increase of capacity factors with pressure.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Metalloporphyrins ; 5,10,15,20-Tetraphenylporphine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The Co(II), Ni(II), Fe(III) and V(IV) complexes of tetraphenylporphine (TPP) can be eluted at short retention times from a LiChrosorb RP-18 column with pure ethanol. However, both Mn(III) and Co(III) complexes of metal TPP chloride type are so strongly retained on the column that they cannot be eluted. While the retention of other metal teraphenylporphine complexes was not affected, that of the metal(III) complexes of the TPP chloride type especially MnTPPCl and CoTPPCl, decreases dramatically with an increase in the concentration of NH4Cl added into the mobile phase; a linear relationship between logk' and log[NH4Cl], with the slope of about−1, has been observed for these two metal(III) complexes in the NH4Cl concentration range from 2.5×10−4 to 1.3×10−2 mol/l. Thus, the specific control of the retention of the metal(III) complexes is enabled by conditioning the NH4Cl content of the mobile phase, and the chromatographic separation is demonstrated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 55-58 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; 1-Octanol/water partition coefficient ; Cellulose acetate ; Reverse osmosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The adsorption properties of esters, aldehydes, ethers and amides on cellulose acetate, which is commonly used as a reverse osmosis membrane material, in an aqueous solution system were measured by high-performance liquid chromatography. The adsorption property was characterized with the specific retention volume. For a noncyclic homologous series the logarithm of the specific retention volume was linearly correlated with the logarithm of the partition coefficient between 1-octanol and water. The fact that the slopes of these regression lines are almost identical confirms that the dominant effect on adsorption is the hydrophobic interaction between cellulose acetate and the solute molecule. The intercept represents the effect of the polar groups on adsorption. The effect of the polar group decreases as follows: ―C(O)O―, ―CO―, HCON〈 〉 CH3CON〈 〉 ―OH, ―O―.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 22 (1986), S. 77-80 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Dihydroartemisine ; Interconversion equilibrium ; Multiple-peaks
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The interconversion between the α- and β-isomers and the multiple-peaks of dihydroartemisinine (dihydroqinghaosu) were investigated in reversed-phase, highperformance liquid chromatography. A convenient method using the Gaussian distribution function instead of the Schmidt graphical method for the theoretical calculation of the “diffuse” probability curves versus the fraction of the dead time on column as β form was introduced. Based on the theoretical probability curves and the experimental multiple-peak chomatograms, the effects of temperature and flow velocity on the accuracy and precision of analysis of dihydroartemisinine are indicated and the activation energy of the interconversion between α- and β-isomers of dihydroartemisinine is estimated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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