Fluorescamine reacts with primary amines to yield a fluorescent product. Treatment of aminosilanized glass and aminosilanized indium tin oxide-coated glass allows the silanized surface to be investigated in situ. Two methods of silanizing these materials were compared. The effect of aqueous solutions on the silanized surface was monitored. The results were used to account for the amount of horseradish peroxidase covalently attached to the surfaces. The N-hydroxysuccinimide ester of ferroceneacetic acid was prepared and covalently attached to aminosilanized indium tin oxide-coated glass, and its electrochemical properties were studied with the aid of fluorescamine.