Preliminary investigations demonstrated that sample clean-up prior to analysis of EGCG in GT extract is crucial due to the presence of polymerised polyphenols that might be formed during GT processing or due to bad storage conditions (Ostadalova et al., 2011). Direct application of the crude extract resulted in permanent colour change of the stationary phase and severely affected the lifetime of the cartridges (results not shown). Caffeine is the second major active component in GT extract and is co-retained on SPE cartridges along with catechins, our target analyte. Structural properties of caffeine and catechins (Fig. 1) indicated that it has more affinity to C18 stationary phase. Preliminary investigations using HPLC supported this observation (results not shown). Thus, decaffeination prior to SPE was suggested as a possible approach to improve the dynamic capacity of the SPE cartridge towards catechins over the expense of caffeine.