A specific colorimetric method for estimation of phlorrhizin in biological fluids

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Abstract
A simple colorimetric method is described for the estimation of phlorrhizin in biological fluids. Phlorrhizin is first brought into solution in borate buffer (pH 9.1). The pH is important both because the rate of the reaction depends on pH and also because the final product acts as an indicator which is green at pH 12, red at pH 9 and yellow at pH 6.5. Since the rate of color development also depends on electrolyte concentration the phlorrhizin is first extracted with butanol, and then re-extracted from the butanol with borate buffer. H2O2 is then added to the borate extract and the color compared with that of a standard phlorrhizin solution treated in a similar way. The method appears to be highly specific for phlorrhizin, and is not given by any phlorrhizin derivative which has been tested.