A Simple Colorimetric Determination of the Free Amino Groups in Water Soluble Chitin Derivatives Using Genipin

A colorimetric method for quantitative measurement of free amino groups of water soluble chitin derivatives is described. The method utilizes genipin as a natural and specific reagent for determining the concentration of free amino groups in samples of water soluble chitin derivatives. The blue color adduct (complex) formed during genipin reaction with free amino groups was measured at about 589 nm and Beer-Lambert's law obeyed over the concentration range of 50 to 300 mg/L. Parameters of analytical conditions were considered and kept constant during the experimental procedure. Highly acetylated water soluble chitin derivatives can be differentiated from water soluble chitosan using this genipin method. The colorimetric method with genipin was proved to be a rapid and efficient technique to determine the free amino groups in water soluble chitin derivatives. This method can also be applied for the detection of the enzymatic activity of chitin-deacetylase.