Fiber-Optic Sensor with a Dye-Modified Chitosan/Poly(vinyl alcohol) Cladding for the Determination of Organic Acids

Abstract

Organic acids in aqueous solution were determined with a fiber-optic sensor having a chitosan/poly(vinyl alcohol) cladding. Interference from ethanol could be reduced by controlling the crosslinking of the cladding with glutaraldehyde and by modifying the cladding with 5′, 5"-dibromopyrogallolsulfonphthalein. The response time for 5v/v% acetic acid was within 1min and the RSD was ca. 2% for 10 successive measurements. Coating of the cladding with an amorphous fluoropolymer increased its durability and removed interferences from inorganic acids and non-volatile compound.