Fluorometric Determination of Zinc, Cadmium and Gallium Ions with a Fiber-Optic Sensor Having a Pyridoxal Isomer-Modified Chitosan/Agarose Gel as a Sensing Probe

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A bifurcated fiber-optic sensor for Zn²⁺, Cd²⁺ and Ga³⁺ ions was fabricated. Chitosan modified with 5-formyl-3-hydroxy-4-hydroxymethyl-2-methylpyridine was immobilized on an agarose gel and used as a fluorogenic probe. The reproducibility of the response to Zn²⁺ was within 5% in eight successive measurements at 5.0×10^-5M (1M=1mol dm^-3). A linear relationship with a correlation coefficient of 0.994 was obtained in the Zn²⁺ concentration range of 0-2.0×10^-5M, and the detection limit was 1.0×10^-6M (S/N=3). Cd²⁺ and Ga³⁺ ions were also detected, though with sensitivities somewhat lower than that for Zn²⁺.