An innovative monolithic zwitterionic stationary phase for the separation of phenolic acids in coffee bean extracts by capillary electrochromatography.
A methacrylate based monolith, containing the innovative zwitterionic monomer (3-allyl-1-imidazol)propane sulfonate, was prepared in 100 μm I.D. silica capillaries by UV initiated photo-polymerization. Composition of the porogen, i.e. a mixture of 1-propanol, 1,4 butanediol and water, was of great importance to obtain a homogeneous monolith with satisfactory permeability and good electrochromatographic performance. Morphology of the stationary phase was studied in Scanning Electron Microscopy and IR experiments, which revealed a good attachment to the capillary wall, flowthrough-pores in the range of 0.5-2 μm, and a continuous monolithic structure. The developed material was well suited for the analysis of six common phenolic acids (salicylic, cinnamic, syringic, rosmarinic, caffeic and chlorogenic acid) by CEC. Their separation was possible in less than 8 min with a mobile phase comprising a 12 mM aqueous ammonium acetate solution with pH 8.5 and acetonitrile, at an applied voltage of - 20 kV. The developed method was validated (R2≥ 0.995; LOD ≤ 3.9 μg mL-1, except for salicylic acid; recovery rates from 94 to 104%) and successfully used for the determination of phenolic acids in Coffea arabica samples. All of them contained cinnamic, syringic and caffeic acid, however only in unroasted coffee beans chlorogenic acid (0.06%) was found. The quantitative results were in good agreement to reported literature data.
Institute of Pharmacy, Pharmacognosy, University of Innsbruck, Innsbruck, Austria.
Adele
A
Murauer
Institute for Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria.
Rania
R
Bakry
Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Austria.
Herwig
H
Schottenberger
Institute for Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria.
Christian
C
Huck
Institute of Pharmacy, Pharmacognosy, University of Innsbruck, Innsbruck, Austria. Electronic address: Markus.Ganzera@uibk.ac.at.
Markus
M
Ganzera
D053801:Capillary Electrochromatography / Q000379:methods*; D003069:Coffee / Q000737:chemistry*; D062385:Hydroxybenzoates / Q000302:isolation & purification*; D007093:Imidazoles / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*
D003069:Coffee; D062385:Hydroxybenzoates; D007093:Imidazoles; D010936:Plant Extracts; C017616:phenolic acid
CEC; Coffee; Natural products; Zwitterionic stationary phase