ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    Springer
    Chromatographia 23 (1987), S. 814-817 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Ammonium tungstophosphate ; Aminoacids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of aminoacids on columns of silica coated with different percentages of ammonium tungstophosphate at several buffer phosphate concentrations is reported. The stationary phase shows a high selectivity towards aminobutyric acids and methyl derivatives of tryptophan due to the distance between the carboxylic group and the −NH 3 + group involved in the cation-exchange process and/or to the steric hindrance by a methyl substituent. A relationship between HPLC and HPTLC data has been verified and applied to the prediction of the separation of six aminoacids.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbidopa and levodopa in plasma ; Electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A validated reversed-phase high-performance liquid chromatographic procedure employing electrochemical detection (LCEC) for the analysis of carbidopa and levodopa in human plasma is reported. The method is sensitive and specific with amperometric detection at a glassy carbon working electrode with Eapp=0.75 V vs. Ag/AgCl. The retention times of levodopa, internal standard, and carbidopa are 3.3, 4.5, and 9.7 minutes, respectively, with an overall chromatographic run time of 12.0 minutes. The peak height ratio versus plasma concentration is linear over the range of 5.0 to 500 ng/mL for each analyte and exhibits correlation coefficients of 0.9957 or better (n=9). The mean absolute recovery of carbidopa and levodopa using the described assay is 36.6 and 66.0%, respectively. The inter- and intra-day accuracy and precision are within 11.8% of the actual values for all concentrations. Also, due to the demonstrated instability of carbidopa and levodopa in plasma a procedure is provided to circumvent this. Blood collected in pre-treated Vacutainer tubes can be stored in an ice bath for up to 4 hours without any significant degradation, thereby providing a practical means for processing several clinical samples simultaneously.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Cyanopropyldimethyl silica ; Chloro-added polycyclic aromatic hydrocarbons ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention characteristics in normal phase HPLC of highly biologically active chloro-added polycyclic aromatic hydrocarbons (PAHs) were studied. Silica, cyanopropyldimethylsilyl- and aminopropylsilyl- modified stationary phases were investigated. Retention properties of chloroadded PAHs on these phases were shown to be strongly influenced by the number of chloro-additions. This is due to the strong polarity of the methylene carbon at the chloro-addition site. Active silica had a strongly degrading effect on the unstable chloro-added PAHs during separation. Aminopropylsilica did not exhibit sufficient selectivity towards chloro-added PAHs when compared to chlorosubstituted PAHs. Cyanopropyldimethylsilica was shown to be applicable to a group separation of chloro-added and chloro-substituted PAHs. A fast clean-up procedure for chloro-added PAHs in complex samplesis outlined. It involves an initial elimination of more polar substances on a short open column with strongly deactivated silica and a subsequent separation on a cyanopropyldimethylsilyl HPLC column in normal phase mode.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 395-399 
    ISSN: 1612-1112
    Keywords: Supercritical fluid extraction ; Column liquid chromatography ; Carbendazime analysis ; Vegetable samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An SFE-HPLC method for the determination of carbendazime in lettuce leaves is described. The method involves a prior lyophilization of the sample and subsequent extraction with supercritical carbon dioxide containing methanol. The extraction conditions are as follows: amount of lyophilized sample, 1 g; CO2 density, 0.75 g/ml; temperature, 50 °C; flow-rate, 1.8 ml/min; dynamic extraction time, 25 min. Carbendazime is determined with an octadecylsilane column, an acetonitrile/water 30∶70 mobile phase and fluorescence detection at 285/317 nm. Carbendazime recoveries from spiked samples were all close to 100%. A comparison with the results from a conventional method for the determination of carbendazime reveals the new method to be more rapid, simple and reproducible for samples with low concentrations of analyte.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 23 (1987), S. 579-582 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Backflush technique ; Coal-derived procucts ; Separation of phenolic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method was developed for the direct extraction of phenolic compounds from coal-derived products and subsequent isocratic HPLC analysis in a reversed-phase system by using the backflush technique.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cyano bonded phases ; Residual silanol groups ; Diethyldithiocarbamates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary When a cyano bonded phase is used together with a nonaqueous eluent, it is universal that the silanol groups which remain at the surface of the silica gel after bonding affect the retention of solutes. With solutes containing such atoms as N, S and O, hydrogen bond may form between the solute and the residual silanol group, leading to dual retention mechanism. Based on the understanding of retention mechanism, methods were developed to separate metal-diethyldithiocarbamate (DDTC) chelates and crown ethers on cyano bonded phase, the mobile phase being a nonaqueous solvent containing triethylamine (TEA).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 27 (1989), S. 316-320 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 27 (1989), S. 509-512 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 32 (1991), S. 453-456 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-exclusion ; Retention ; Adsorption effects ; Dicarboxylic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention values and distribution coefficients for C4−C9 dicarboxylic acids on a column packed with cation exchange resin in the H+ form were determined, using dilute HCl solution as eluent. Based on the Donnan membrane equilibrium and adsorption equilibrium, adsorption coefficients were evaluated, and the adsorption contributions to the retention of these analytes were estimated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...