ABSTRACT
A high-performance liquid chromatographic (HPLC) method was developed for the quantitative comparison of various batches of tannic acid from the same manufacturer used to aid the binding of human chorionic gonadotropin to sheep erythrocytes in the manufacture of pregnancy testing kits. The tannic acids were separated by reversed-phase HPLC on a C18 column using gradient elution with aqueous methanolic eluents at low pH. A portion of the chromatogram corresponding to the compounds involved in the tanninisation process was integrated and a linear relationship was established between this peak area and tannic acid concentration. The correlation coefficient was greater than 0.993 even in the absence of an internal standard. Tanning capacity was evaluated on the basis of the amount of tannic acid which remained following incubation with a known quantity of erythrocytes. The application of this procedure to three batches of tannic acid is demonstrated.
