rapid determination of nitrate by colorimetric thin film based on sol-gel method

Abstract: nitrate has been added intentionally at the curing process of certain meat products, due to their ability to inhibit the outgrowth spores of clostridium botulinum and to impart characteristic color and flavor to this kind of foodstuffs. the significance of nitrate to human health is related to the fact that nitrate, after being metabolized or reduced to nitrite, can react with secondary or tertiary amines to form n-nitroso compounds, which are potent carcinogens. we herein describe the fabrication of a brucine incorporated sol-gel glass with nanoporous structure as an optical sensor to measure nitrate. tetraethyl orthosilicate was used as precursor to form the porous polymeric network for entrapment of brucine in porous silica gel matrix. in order to modify pore size, quality and leaching behavior of the sol-gel network, several sols were prepared with different sol-gel phs and water: alkoxide ratios. our thorough experimental-based results revealed that the porous feature of the matrix as well as its average pore size could play significant roles in almost all critical parameters, affecting the sensor performance, including sensitivity, selectivity and response time of sensor. the fe-sem technique equipped with edax was also employed to evaluate the surface morphology, porosity growth and elemental identification of the thin films. the constructed sensors showed optimum performance under the working conditions, including water: alkoxide ratio of 4:1, water acidity of 1 m. under optimum conditions, a linear calibration curve over the range 2.0 to 8.8 μg ml−1 of nitrate was obtained, along with a detection limit value of 0.5 μg ml−1. meanwhile, the sensor exhibited excellent rsds for both intra-day and inter-day precision.