Behavior of α‐Naphtholphthalein as Analytical pH‐Indicator Entrapped into Sol Gel Matrix

This study considers the nature of interactions between the sol gel derived inorganic matrix and α‐naphtholphthalein pH‐indicator, the method is based on the physical entrapment of the indicator molecules in sol gel matrix, the immobilized α‐naphtholphthalein pH‐indicator shows similar behavior as its solution counterpart. The UV/VIS spectra indicate that the α‐naphtholphthalein retains its structure during the sol gel reactions in terms of response to pH. α‐Naphtholphthalein can be regarded as uniformly distributed in the sol gel matrix. This observation has been confirmed using polarized microscopy.

Keywords:

• α‐Naphtholphthalein pH‐indicator
• immobilization of indicators
• sol gel entrapment