Effective purification of ellagic acid by successive automatic recrystallization and absolute determination of purity by absorptivity ratio

A novel approach to the determination of absolute purity by repeated purifications with an automatic recrystallization method is proposed. A unique method for purity determination requiring no reference standards is developed and theoretical considerations are presented. This involves the measurement of spectrophotometric molar absorptivities of consecutively recrystallized samples and extrapolating the absorptivity to obtain epsilon(infinity), corresponding to the 100% pure material. purity is then determined by the ratio epsilon(s)/epsilon(infinity), where epsilon(s) is the absorptivity of the impure sample. Several experimental measurements for ellagic acid are presented. Excellent agreement between the purity values of commercial samples determined by the proposed method and values measured by a liquid chromatographic method was obtained. The purity of two commercial ellagic acid samples and a four times recrystallized product evaluated were 97.7%, 98.1%, and 100.1% respectively.