A Highly Sensitive Optical Chemical Sensor Based on Organically Modified Silicate Film for Trace Amounts of Nitrite

Background: Nitrite is a carcinogenic compound and can be found in water, soil, and food products. Determining the presence of nitrite has become very important in monitoring water quality and food safety. Methods: A highly sensitive optical chemical sensor based on sol-gel film for trace amounts of nitrite was developed. The Xylene cyanol FF dye doped organic-inorganic silica hybrid film was obtained by copolymerization of tetraethoxysilane (TEOS) with methyltriethoxysilane (MTEOS) as an organically modified sol-gel precursor, and deposited onto glass substrates using spin-coating techniques. Results: The organically modified silicate thin film prepared with a 2:1 TEOS: MTEOS volume ratio was found to be the best in terms of transparency, uniformity, and stability. The organically modified silicate thin film changes from blue to yellow when added to a nitrite aqueous solution, causing decreased absorbance of the film at 618 nm. The experimental results show that the film has a good linear response (R-2 = 0.9833) to nitrite in the range of 10 to 0.1 mu g. L-1. Conclusion: The XCFF dye doped sol-gel film has high sensitivity, selectivity for nitrite in the water samples. The detection limit of film for nitrite was found to be 0.011 mu g. L-1 (0.24 nmol. L-1). This sol-gel film is stable, inexpensive, and easily fabricated. It could be practical used for the determination of nitrite in most real water samples.