Label-free colorimetric detection of glutathione by autocatalytic oxidation of o-phenylenediamine based on Au3+ regulation and its application

A label-free, rapid, and highly sensitive colorimetric assay for the detection of glutathione (GSH) was developed.

Kinetics and mechanism of oxidation of creatine by N-Bromosuccinimide in acidic aqueous medium

The kinetics and the mechanism of oxidation of creatine (AA) by N-Bromosuccinimide (NBS) in an acidic aqueous medium were examined under isolation conditions. Iodometric method was used to follow the unconsumed NBS at different time intervals. Mercuric(II) acetate was used as a scavenger to capture any Br- formed during the reaction and hence to avoid autocatalytic oxidation by bromine. Findings from stoichiometry measurements revealed that the reaction between AA and NBS was a 2:1 molar ratio. The kinetic study showed that the reaction was first order with respect to both AA and NBS. Increasing [H+] had a negative effect on the rate of reaction. The effect that varying the solvent composition has on the rate of reaction was investigated, and it was found that the reaction rate decreased as the dielectric constant of the solvent increased. The temperature dependence was determined under fixed experimental conditions, from which thermodynamic parameters were calculated. From the proposed mechanism, a rate law was established that was in strong agreement with experimental kinetics.

Wavelength selective photoactivated autocatalytic oxidation of 5,12-dihydrobenzo[b]phenazine and its application in metal-free synthesis

We describe the photoactivated autocatalytic oxidation of 5,12-dihydrobenzo[b]phenazine to benzo[b]phenazine with oxygen from the air as the oxidant and develop a green synthesis way of metal impurity-free BP or other similar products.

Dynamics of gas release during thermal oxidation of TBP solutions in Isopar-M in two-phase system

ABSTRACTThe dynamics of the gas release at thermal oxidation of the two-phase systems of 30% solution of tri-n-butyl phosphate (TBP) in isoparaffinic diluent Isopar M – aqueous solution of 4.3, 8.2 and 12 mol/L of HNO3 has been investigated within the temperature range from 70°C to 110°C. The effect of pre-irradiation of the system TBP–Isopar-M–HNO3 on the kinetics of its thermolysis has been determined. All of the samples were irradiated with an electron accelerator at a dose rate of 10 kGy/h up to integrated doses of 0.5, 1 and 2 MGy. The parameters of heat and gas emission during thermolysis of the tested extraction system in an open apparatus have been determined experimentally. It has been demonstrated, that there are no conditions for extension of autocatalytic oxidation under heat treatment of two-phase extraction systems in open vessels.

Biofiltration field study for cold Fe(II)- and Mn(II)-rich groundwater: accelerated Mn(II) removal kinetics and cold-adapted Mn(II)-oxidizing microbial populations

Removal of Mn(II) from Fe(II)- and Mn(II)-rich groundwater in cold regions is challenging, due to slow Mn(II) removal kinetics below 15 °C. This study demonstrated onset, acclimation, and acceleration of Mn(II) removal in a two-stage pilot-scale biofilter (Fe and Mn filters) at varying low on-site temperatures (8–14.8 °C). Mn(II) removal commenced at 8 °C in the Mn filter after Fe(II) removal. A shift in redox-pH conditions favored biological Mn(II) removal and Mn(II)-oxidizing bacteria increased. The Mn filter reached steady-state functioning after 97 days, exhibiting high removal efficiencies (97 ± 0.9%). Yet, first-order rate constants (k) for Mn(II) removal were low (10−6–10−5 min−1; t1/2 = ∼40 d). After consecutive backwashes and filter inoculation with backwashed sludge, k remarkably accelerated to 0.21 min−1 (t1/2 = 3.31 min at 11 ± 0.6 °C). The cold-adapted microbial consortium (51 genera), including Pseudomonas, Leptothrix, Flavobacterium, and Zoogloea, cultured from the field-aged biofilter rapidly produced biogenic Mn oxides at 8 °C, confirmed by electron paramagnetic resonance spectroscopy. Birnessite and pyrolusite detected by synchrotron-based powder X-ray diffraction, and a repetitive birnessite-like surface morphology on ripened filter materials, reflected autocatalytic oxidation. Shifting in k indicated the vertical progress of biofilter ripening, which was not limited by low temperature.