The laboratory reproducibility of the method (for ferulic
acid, internal-laboratory standard deviation for 1 month of the
studies)was in the range of 3.5e6.0%. Within-one-day repeatability
and reproducibility of the HPLC method, calculated using vanillic,
caffeic, chlorogenic and p-coumaric acid standards was below 6.0% and was acceptable for this study. Quantitative analysis was performed
in duplicate.