Design and fabrication of a new sol-gel based sensor for the visual detection of oxalate and investigation of the effect of boiling on the oxalate content of some foods

Sol-gel chemistry is a unique method for constructing high-performance flexible sensors. Sol-gel silica matrices doped with a controlled amount of sensing agent (dopant) lead to the fabrication of suitable sensors. According to this knowledge, we decided to describe the development and performance characteristics of the sol-gel glasses with a nanoporous structure as the novel naked eye sensor for fast detection of oxalate based on the incorporation of indole inside pores of the silica matrix obtained by sol-gel technology. Several sols were made with different water: alkoxide ratios and pHs to design a highly sensitive and selective thin film without dopant leaching. The Field emission scanning electron microscopy (FE-SEM) technique was employed to evaluate the surface morphology and porosity growth. Also, the sol-gel films were characterized by Fourier-transform infrared (FTIR) spectroscopy. The optimum performance in terms of sensitivity, leaching, and response time was achieved using water: alkoxide ratio of 4:1, water acidity (HCl concentration) of 0.01 M, and ethanolic solution of Indole 0.01 mol L-1. The calibration plot was obtained within 0.01-6.00 mu g mL-1 of oxalate with a detection limit value of 0.005 mu g mL-1. Meanwhile, the prepared sensor exhibited excellent and acceptable RSDs for both inter-day and intra-day precision. The present sensor was used to measure oxalate in various samples and investigate the effects of the celery & apos;s cooking time and the brewing duration of tea on oxalate content.

Automated summary

Sol-gel chemistry is a unique method for constructing high-performance flexible sensors. This study successfully developed a novel naked eye sensor for fast detection of oxalate by incorporating indole inside the pores of sol-gel silica glasses. The sol-gel films exhibited excellent sensitivity, leaching resistance, and response time under optimized conditions. The prepared sensor showed a wide detection range and low detection limit for oxalate, and displayed good precision for both inter-day and intra-day measurements.