A ultraviolet spectrophotometric method for the measurement of hydroxypropyl-β-cyclodextrin's degree of substitution

Using 1,2-propanediol as a benchmark to draw standard curve and purified single-substituted and dual-substituted hydroxypropyl-beta-cyclodextrins as standard samples, a spectrophotometric method was established to measure the degree of substitution of hydroxypropyl-beta-cyclodextrins. Hydroxypropyl-beta-cyclodextrins reacted to oil of vitriol in 100 degrees C water bath for 3 min, then added 3% ninhydrin solution after cooling and stood in 25 degrees C water bath for color. Using 1 cm of colorimetric cuvette menstruated the absorbancy at 588 nm. The quantity of 1, 2-propanediol was gained by checking standard curve, and the degree of substitution was gained by conversion. The relative deviation of measuring the degrees of substitution of single-substituted and dual-substituted hydroxypropyl-beta-cyclodextrins were 6. 67% and 2. 81%, respectively. By this method, a series of hydroxypropyl-beta-cyclodextrins with different degrees of substitution were measured. The results were compared with those gained from the method of NMR and mass spectrometry. This method is available to mensurate the degree of substitution of hydroxypropyl-beta-cyclodextrin.