Analytical methods of green tea for the determination of caffeine, catechins, free reducing sugars, vatimin C, water soluble pectin, amino acids and conversion rate of chlorophyll to pheophytin were submitted to a collaborative study in which three collaborators participated.
Collaborators were instructed to perform the analysis in triplicate on three differrent days about four samples with each method.
The precision and the permissible tolerance of each method were calculated by ststistical treatment of the data.
The precisions within and between laboratories were satisfactory in analytical method of caffeine. These precisions were camparatively high in that of amino acids. The precisions within laboratory were satisfactory in those of catechins and vitamin C, however, the pricisions between laboratories were insufficient in these methods.
The determined values of free reducing sugars, water soluble pectin and conversion rate of chlorophyll to pheophytin were considerably varied with each collaborator.
The permissible tolerances between three laboratories were under 10% of determined values in analytical methods of caffeine and amino adids.
Therefore, the analytical method of caffeine can be adopted as a standard method. That of amino acids can be applied for a special usage without general application, because the values obtained by tested method are higher than that obtained by amino acids analyzer. Further improvements were necessary as to other analytical methods.
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