The final extraction conditions were as follows: the presence of
stirring, 100 C as extraction temperature, 500Was system power,
25 mL as extraction volume, 40% methanol in water as extraction
solvent and 5 min as extraction time. Using these extraction conditions,
the repeatability and the reproducibility of the method
developed were determined by carrying out a total of 15 extractions,
nine on the first day and a further three on each of the following
two days. The results as regards the relative standard
deviation of the areas of the chromatographic peaks for intraday
analyses were found between 0.9% (Peonidin 3-glucoside) and
6.8% (Cyanidin 3-glucoside). For interday analyses the relative
standard deviation were found ranging from 3.0% (Delphinidin 3-
glucoside) and 8.5% (Malvidin 3-coumaroylglucoside).
It can be observed that the best variation found for the glucosides
is below 7%, whilst for the acyl derivatives it is below 9%.
The greatest variation found for the acyl derivatives could be
attributed generally to the smaller chromatographic area of these
compounds.