Studying the Adsorption Process of Riboflavin on Silver-Deposited Fe3O4 Nanoparticles

The adsorption characteristics of riboflavin onto silver-deposited iron oxide magnetic nanoparticles (Ag/Fe3O4) have been described. Characterization of the synthesized Ag/Fe3O4 nanoparticles was achieved by FTIR spectra, TEM image and XRD pattern. The influence of several experimental parameters such as nanoparticles dosage, pH of the sample solution, different orientations of the riboflavin molecules toward Ag/Fe3O4 surface, riboflavin concentration, contact time of the reagents, temperature, ionic strength and presence of halide anions were studied. Experimental data indicated that Ag/Fe3O4 nanoparticles adsorb more than 90% of riboflavin under the optimum experimental conditions of the adsorbent dosage of 4.0 mg, a pH of 6.0, and a contact time of 2.0 min, when an initial riboflavin concentration of 0.02 mM is used. The results revealed that the presence of halide anions lower the adsorption of riboflavin on the surface of nanoparticles due to dissolution of the silver layer of the nanoparticles. It was found that the adsorption isotherm is best fitted to Dubinin-Radushkevich and Freundlich models and kinetic model followed a pseudo-second-order adsorption rate

Simultaneous Determination of Thiocyanate and Oxalate in Urine using a Carbon Ionic Liquid Electrode Modified with TiO2-Fe Nanoparticles

A carbon ionic liquid electrode (CILE) modified with TiO2-Fe nanoparticles was constructed by incorporating TiO2-Fe nanoparticles into the paste matrix. Under the optimized experimental conditions, using differential pulse voltammetry (DPV), the oxidation of thiocyanate and oxalate were occurred at potentials of 0.740 V and 1.010 V, respectively, at the surface of the modified electrode. Observing a high peak current along with a suitable peak separation allowed introducing the first voltammetric sensor for simultaneous determination of these anions with high sensitivity without mutual interference. A wide linear range of 1.0 × 10-5-1.8 × 10-3 M for thiocyanate with a detection limit of 6.4 × 10-6 Mand a wide linear range of 5.0 × 10-5-3.0 × 10-3 M for oxalate with a detection limit of 2.3 × 10-5 M were obtained. The modified CILE showed good reproducibility, repeatability and storage stability as well as good selectivity. The proposed sensor was successfully applied for analysis of thiocyanate and oxalate in urine samples

Simultaneous Determination of Chlorpyrifos and Carbaryl by Spectrophotometry and Boosting Partial Least Squares

Residue of pesticide has posed a serious threat to human health. Fast detection methods are necessary for the various types of pesticide. This study investigated the feasibility of the combination of spectrophotometry and boosting partial least squares method (boosting-PLS) for the simultaneous determination of chlorpyrifos and carbaryl, two of the most important pesticides in agriculture. Effect of pH on the absorbance spectra of each component was studied and pH 5 was selected as optimum. To build boosting-PLS models, thirty six binary mixtures were used and to validate the resulted models, twenty binary mixtures were employed. Results for boosting-PLS were compared to ones obtained for full-spectrum PLS and PLS algorithm coupled with tabu search (TS) as wavelength selection tool. In spite of the improvement by both boosting and wavelength selection approaches, the prediction ability of PLS algorithm, the boosting-PLS is superior to the other models. Boosting-PLS is not only feasible but also can avoid doing wavelength selection in such a task