One-Pot Synthesis of Tannic Acid-Au Nanoparticles for the Colorimetric Determination of Hydrogen Peroxide and Glucose.

This study introduces a novel one-pot method employing tannic acid (TA) to synthesize stable gold nanoparticles (TA-AuNPs), which are characterized using transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. We apply these TA-AuNPs in a newly developed colorimetric assay for hydrogen peroxide (H2O2) detection that utilizes the oxidation of iodide (I-) on TA-AuNPs, leading to a detectable yellow color change in the solution. The reaction kinetics are captured by the rate equation R = 0.217[KI]0.61[H2O2]0.69. The possible sensing mechanism was proposed through density functional theory calculations. At the optimum conditions, the proposed TA-AuNPs/I- system demonstrated a linear relationship between H2O2 concentration and absorbance intensity (λ = 350 nm) and achieved a limit of detection (LOD) of 7.33 µM. Furthermore, we expand the utility of this approach to glucose detection by integrating glucose oxidase into the system, resulting in a LOD of 10.0 µM. Application of this method to actual urine samples yielded spiked recovery rates ranging from 96.6-102.0% and relative standard deviations between 3.00-8.34%, underscoring its efficacy and potential for real-world bioanalytical challenges.

Removal of metal ions from the complexed solutions in fixed bed using a strong-acid ion exchange resin.

Fixed bed removal of equimolar metal ions (Co(2+), Ni(2+), Mn(2+), Sr(2+)) from aqueous solutions using a strong-acid resin was examined. The solution contained a water-soluble complexing agent including ethylenediaminetetraacetic acid, nitrilotriacetic acid, and citric acid. Experiments were performed under different solution pH and molar concentration ratios of complexing agent to the total metals. It was shown from batch studies that the equilibrium exchange of metals and the resin mainly depended on solution pH, and partly on the type of complexing agent used. A mass transfer model was proposed to describe the breakthrough curves of the resin bed, which contained two parameters (tau and k) estimated from the observed breakthrough data. The calculated breakthrough curves agreed well with the measured ones (standard deviation <6%). In fixed bed tests at low pH (=2), the type of complexing agent had little effect on the breakthrough data. For a given complexing agent, the metal with a larger overall formation constant (K(f)) showed a smaller exchange capacity. For a given metal ion, the complexing agent with a larger K(f) also revealed a smaller exchange capacity.