Colorimetry of Total Phenolics with Phosphomolybdic-Phosphotungstic Acid Reagents

Several details of the assay of total phenolic substances have been investigated and an improved procedure developed. The improvements include the use of Folin-Ciocalteu reagent rather than the Folin-Denis reagent, gallic acid as a reference standard, and a more reproducible time-temperature color development period. The values obtained are less subject to variation and interference from several nonphenols, yet are directly comparable to the "tannin" values obtained by the previously standard method.