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
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 5-10 
    ISSN: 1040-7685
    Keywords: caffeine ; coffee ; micellar electrokinetic capillary chromatography (MECC) ; reproducibility ; HPLC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Samples of regular and decaffeinated varieties of green coffee beans, instant coffee, and “roast & grind” coffee have been examined by micellar electrokinetic capillary chromatography (MECC). The separation conditions affecting the reproducibility of the determination of caffeine in these samples are presented. Sodium dodecyl sulfate (SDS) and cetyltrimethylammonium chloride (CTAC) Were employed to demonstrate the role of the surfactant system in reproducibility. The use of NaOH and HCl was explored for column rinsing to enhance the stability of the electroosmotic flow. The levels of caffeine ranged from 3.95% (by weight) for regular coffee to 0.07% for decaffeinated coffee. The relative standard deviation (RSD) for the migration time of the peak corresponding to caffeine in coffee samples was 0.74%. The RSDs for the peak areas and heights were 1.04 and 2.07%, respectively. The results of the quantitation of caffeine by MECC are compared to levels determined by high-performance liquid chromatography (HPLC).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 523-528 
    ISSN: 0935-6304
    Keywords: Nonaqueous solvents ; Capillary electrophoresis ; Capillary electrochromatography ; Current measurement ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvents acetonitrile, methanol, N, N-dimethylformamide, dimethyl sulfoxide, formamide, and deionized water were investigated for their ability to support current flow without added electrolyte. Using open tubular capillary electrophoresis, currents were measured to be in the nanoampere (10-9 A) range for all solvents but formamide (10-6 A). Comparisons with flow data showed no clear relationship between current and electroosmotic flow. Packed capillary columns (3-μm ODS) were used for separations using both pure solvent and hydrophobic dyes showed mild retention in pure ACN. A 16 polynuclear aromatic hydrocarbon (PAH) standard soluton was separated in 80/20 ACN/H2O with reduced plate heights (h) between 2.8 and 3.1 for retained species. A separation of nine androstenediones was achieved using a 70/30 MeOH/H2O mobile phase.
    Additional Material: 6 Ill.
    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...