Selective elution of tea catechins and caffeine from polyvinylpolypyrrolidone

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Desorption of catechins and caffeine from polyvinylpolypyrrolidone (PVPP) was comprehensively investigated. The result showed that caffeine could easily be desorbed from PVPP by the tested solvents except n-hexane, while catechins could only be thoroughly done by dimethyl sulphoxide (DMSO) and N, N-dimethylformamide (DMF). Excellent desorption efficiency of DMSO and DMF might be attributed to their high dipole moments and H-bond potentials. Addition of ethanol was recommended considering the elution efficiency and fluidity, but ethanol volume should be <40% (v/v) for DMSO or 20% (v/v) for DMF. Desorption would get to equilibrium within 1 h and followed the pseudo-second-order model. Caffeine and catechins could be separately desorbed through two-stage elution procedure, that is, water or 20% aqueous ethanol for desorbing caffeine and part of nongalloylated catechins and DMSO/ethanol (8/2, v/v) for eluting the remaining catechins. Highly purified catechins (˜95%) with high level (˜70%) galloylated catechins would be achieved when the desorption procedure was applied in column chromatograph.

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