MS was used for identification in positive ion mode, and DAD
was used for quantification at wavelength of 210 nm. Linearity for
standards was determined with seven data points over the concentration
range of the working solutions. Repeatability was evaluated
by six injections of the sample solution (GT1) within one day.
Reproducibility was evaluated in intra- and inter-day assays of the
tea sample GT1. The stability test was performed by analyzing the
sample solution (GT1) over period of 24 h. The relative standard
deviation (RSD) was taken as the measures of precision, repeatability
and stability. To determine the recoveries, sample GT1
spiked with standards at low, middle and high concentration levels
in three replicates were extracted and analyzed. Recovery was
calculated by dividing the amount of analyte found in the spiked
sample by the sum of the amount originally found in the sample
plus the amount spiked. All tea samples were analyzed using the
described method.