Development and validation of UHPLC-MS/MS method for determination of eight naturally occurring catechin derivatives in various tea samples and the role of matrix effects

A complete analytical procedure combining optimized tea infusion preparation and validated UHPLC-MS/MS method was developed for routine quantification of eight naturally occurring catechin derivatives in various tea samples. The preparation of tea infusions was optimized in terms of temperature, time and water-to-tea ratio in green, white and black teas. The catechins were analyzed using ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry in a run of only 4 min including equilibration of the system. The UHPLC-MS/MS method was fully validated in terms of inter/intra-day precision, accuracy, linearity (r(2)>0.9991), range (50-5000 ng/ml), LOD (1.5-7.5 ng/ml) and LOQ (5-25 ng/ml). Validation of the method included also the determination of the matrix effects that were evaluated in both flavored and unflavored green, white and black teas. Dilution of the resulting tea infusions appeared to be crucial for the matrix effects and also for subsequent catechin quantification in real tea samples in order to fit into the linear range of the UHPLC-MS/MS method. This complete procedure for catechin quantification was finally applied to real sample analysis represented by 70 commercial tea samples.