This collaborative study was conducted to determine the total monomeric anthocyanin concentration by the pH differential method, which
is a rapid and simple spectrophotometric method based on the anthocyanin structural
transformation that occurs with a change in pH(colored at pH 1.0 and colorless at pH 4.5). Eleven collaborators representing commercial laboratories, academic institutions, and
government laboratories participated. Seven Youden pair materials representing fruit juices,beverages, natural colorants, and wines weretested. The repeatability relative standard deviation(RSDr) varied from 1.06 to 4.16%. Thereproducibility relative standard deviation (RSDR)ranged from 2.69 to 10.12%. The HorRat valueswere !1.33 for all materials. The Study Directorrecommends that the method be adopted Official