Abstract
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.
Highlights
Despite the fact that Capillary Electrochromatography (CEC) is an attractive research area for academia, it is still barely relevant for daily life analysis
That CEC is suitable for the analysis of natural products has been shown in several publications, for example reporting on the determination of coumarins in Angelica dahurica [5], adrenergic amines in Citrus aurantium [6] or flavonoids in liquorice roots [7]
In order to overcome this problem, water was added to the binary porogenic solvents consisting of 1-propanol/1,4 butanediol to yield a homogeneous monolith exhibiting satisfactory permeability and good electrochromatographic performance
Summary
Despite the fact that Capillary Electrochromatography (CEC) is an attractive research area for academia, it is still barely relevant for daily life analysis. Many desirable features like high selectivity, versatility in respect to stationary phases and detection as well as an economic operation compete against not always applicable but severe disadvantages (limited reproducibility and robustness, availability of capillaries, etc.). Only practically relevant applications will promote the routine use of CEC. Their number is manageable, so that this technique is often considered as an exotic rather than an equivalent alternative. When talking about challenging matrices for analysis natural products and their determination in biological samples (e.g. plants) are a good example. This is because their composition is usually complex, relevant compounds are sometimes present in small amounts, and they often show a high degree of structural similarity. That CEC is suitable for the analysis of natural products has been shown in several publications, for example reporting on the determination of coumarins in Angelica dahurica [5], adrenergic amines in Citrus aurantium [6] or flavonoids in liquorice roots [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
