Polymethacrylate Colorimetric Sensor for Evaluation of Total Antioxidant Capacity

A new colorimetric sensor using an immobilized chromogenic redox reagent was devised for measuring the total antioxidant level in a liquid sample without requiring sample pretreatment. The reagent, Fe(III) – 1,10-phenanthroline (Fe(III)-phen), was immobilized into a polymethacrylate matrix (PMM), and the absorbance changes associated with the formation of the highly colored Fe(II)-phen chelate as a result of reaction with antioxidants was measured at 510 nm. The developed optical sensor was used to screen total antioxidant capacity of some black and green teas, red and white wines

Solid Phase Sorption of Phenols on Metals Acetylacetonates

The solid phase extraction properties of surface layers of Eu(III), Al(III), Fe(III), Cr(III) acetylacetonates are compared for sorption some phenols and chlorophenols. The effects of the energies of adsorption and complexation on the retention of various sorbates were calculated. GC methods with preconcentration are proposed to evaluate phenols by means of solid-phase extraction on a sorbent with a surface layer of Eu acetylacetonate with extraction effectiveness of 85%

Solid-phase spectrophotometric iodometric determination of nitrite and selenium(IV) using a polymethacrylate matrix

Procedures for the iodometric solid-phase spectrophotometric determination of nitrite and selenium( IV) using a polymethacrylate matrix are proposed. The procedures are based on the reaction of nitrite and selenium(IV) with iodine in an acidic medium with the release of free iodine in amounts equivalent to those of the substances to be determined, extraction of the iodine formed with a polymethacrylate matrix, and measurement of absorbance of the matrix at 370 nm. The developed procedures ensure the determination of 0.01–0.12 mg/L of nitrite and 0.05–0.40 mg/L of selenium(IV) with limits of detection of 0.005 and 0.03 mg/L, respectively. It was shown that the proposed procedures can be applied to the determination of selenium(IV) in mineral water and nitrites in vegetables and soil

Effect of polyethylene glycol immobilized into a polymethacrylate matrix on the sorption of rhodamine

Combined matrix PMMA and PEG, having a polymethacrylate backbone and hydrophilic PEG chains, has been synthesized and applied for the design of transparent colour sensors. Introduction of the hydrophilic PEG chains in the PMMA bulk overcomes the limitations caused by the hydrophobicity of PMMA, and exhibits good wettability, stable and specific adsorption. We suppose that the adsorption of rhodamine on such networks depends on the chemical composition of the system and describes the interaction of the xanthene dye with the polymers

The Process of Acetonitrile Synthesis over γ-Al[2]O[3] Promoted by Phosphoric Acid Catalysts

The influence of principal parameters (reaction temperature, ratio of acetic acid and ammonia, composition of reactionary mixture and promotion of catalysts) on the selectivity and yield of the desired product was studied in the reaction of catalytic acetonitrile synthesis by ammonolysis of acetic acid. The processing of [gamma]-Al[2]O[3] by phosphoric acid increases amount of the centers, on which carries out reaction of acetamide dehydration. The kinetic model of a limiting stage of reaction - the acetamide dehydration to acetonitrile was suggested. In the process of ammonolysis of acetic acid it was demonstrated that the use of catalysts promoted by phosphoric acid and ratio NH[3]:CH[3]COOH=(3-4):1 at temperatures of a reactor 360-390°С leads to the increase of acetonitrile productivity to 0.7-0.8 g/cm{3}·h and allows to minimize formation of by-products

Application of Humic Sorbents for Pb{2+}, Cu{2+} and Hg{2+} Ions Preconcentration from Aqueous Solutions

The sorbent prepared by sequential treatment of silica gel by polyhexamethylene guanidine of linear structure and humic acids is suggested for sorption concentration of metal ions (Pb{2+}, Cu{2+} and Hg{2+}) from aqueous solutions. Thermogravimetry and infrared spectroscopy have confirmed the success of the attachment of the humic acids onto modified silica surface. Sorption isotherms of lead (II), copper (II) and mercury (II) obtained in optimal conditions of metals sorption were analyzed by using Freundlich and Langmuir adsorption isotherms. Structural model of surface of humic sorbent was proposed based on the obtained results. The results demonstrated the potential applicability of supramolecular humic sorbent in the preconcentration of metal ions from aqueous solution

Solid Phase Sorption of Phenols on Metals Acetylacetonates

The solid phase extraction properties of surface layers of Eu(III), Al(III), Fe(III), Cr(III) acetylacetonates are compared for sorption some phenols and chlorophenols. The effects of the energies of adsorption and complexation on the retention of various sorbates were calculated. GC methods with preconcentration are proposed to evaluate phenols by means of solid-phase extraction on a sorbent with a surface layer of Eu acetylacetonate with extraction effectiveness of 85%