Modifications in the Phenolphthalein Method for Spectrophotometric Estimation of Beta Cyclodextrin

Abstract The phenolphthalein solution used in the assay of β‐Cyclodextrin is not stable and undergoes spontaneous decolorization. There is linear decrease in absorbance of phenolphthalein with time. This causes a continuous increase in error with time which is as high as 80% after one hour. A simple procedure is described in the paper to circumvent this problem allowing reproducible and reliable results to be obtained. A single reagent assay was developed by incorporating phenolphthalein in Na 2 CO 3 solution. This resulted in stable absorbance readings and increased the linearity of assay up to 200μg/ml of β‐cyclodextrin.