Slavica M. Blagojević

Spectrophotometric Investigation of the Pd(II)-Quercetin Complex in 50% Ethanol

Summary. Composition and stability constant of the Pd(II)-quercetin complex were determined by suitable spectrophotometric methods and pH-metric measurements in 50% Ethanol. It was found that the Pd2+ ion and quercetin form a 1:1 complex in which Pd2+ is linked to quercetin through the carbonyl and the 3-hydroxyl group. The stability constant log β1 ranged from 6.05 at pH=5.00 to 4.96 at pH=6.50. The conditions for the spectrophotometric determination of quercetin by means of complex formation were investigated. Beer’s law was obeyed up to 5.00×10−5 M quercetin.Zusammenfassung. Zusammensetzung und Stabilitätskonstante des Pd(II)-Quercetin-Komplexes in 50% Ethanol wurden mittels geeigneter spektrophotometrischer Methoden und pH-metrischer Messungen bestimmt. Es wurde festgestellt, daβ Pd2+ und Quercetin einen 1:1-Komplex bilden, in dem das Pd-Ion über seine Carbonyl- und 3-Hydroxylgruppe an Quercetin gebunden ist. Die Stabilitätskonstante log β1 bewegte sich im Bereich von 6.05 (pH=5.00) bis 4.96 (pH=6.50). Die Bedingungen für eine spektrophotometrische Bestimmung von Quercetin mittels Komplexierung wurden untersucht. Das Beersche Gesetz wird bis zu 5.00×10−5 M Quercetin befolgt.

Current rates and reaction rates in the Stoichiometric Network Analysis (SNA)

Abstract In stoichiometric network analysis (SNA) the instability condition is calculated by the current rates. Recently, we have shown that in the final result the current rates can be substituted by reaction rates, which is a more appropriate value for the examination of instability from experimental point of view. Here, we elaborate the problem of whether the current rates are necessary parameters in the calculation, with the aim of obtaining the region of instability. All calculations are performed on a model for Belousov-Zhabotinsky (BZ) reaction, which has not been examined by SNA.

Temperature influence on the malonic acid decomposition in the Belousov-Zhabotinsky reaction

The kinetic investigations of the malonic acid decomposition (8.00 × 10−3 mol dm−3 ≤ [CH2(COOH)2]0 ≤ 4.30 × 10−2 mol dm−3) in the Belousov-Zhabotinsky (BZ) system in the presence of bromate, bromide, sulfuric acid and cerium sulfate, were performed in the isothermal closed well stirred reactor at different temperatures (25.0°C ≤ T ≤ 45.0°C). The formal kinetics of the overall BZ reaction, and particularly kinetics in characteristic periods of BZ reaction, based on the analyses of the bromide oscillograms, was accomplished. The evolution as well as the rate constants and the apparent activation energies of the reactions, which exist in the preoscillatory and oscillatory periods, are also successfully calculated by numerical simulations. Simulations are based on the model including the Br2O species.

Influence of most important radicals on the numerically simulated belousov-zhabotinsky oscillatory reaction under batch conditions

In the already proposed model of the Belousov-Zhabotinsky reaction with the Br2O species as intermediate one, the reactions with malonyl (MA·), bromomalonyl (BrMA·) and tartronyl (TA·) radicals were introduced with aim to explore their role in overall dynamics. The related numerical simulations of the experimentally obtained dynamic states under batch conditions were successfully performed.

Numerical evidence of complex nonlinear phenomena of the Belousov-Zhabotinsky oscillatory reaction under batch conditions

By numerical calculations based on our previously proposed model with Br2O intermediate species we were able to simulate complex evolution of the Belousov-Zhabotinsky (BZ) reaction under batch conditions. In the defined region of initial malonic acid concentration [MA]0 (1.00 × 10−3 mol dm3 ≤ [MA]0 ≤ 1.50 mol dm−3) different sequences of regular and complex periodic and aperiodic oscillations were obtained. It is noticed that the bromine evaporation significantly affects the dynamics of the reaction.

Return map analysis of the highly nonlinear Bray–Liebhafsky reaction model

By numerically simulated Bray–Liebhafsky (BL) reaction under a continuously fed well stirred tank reactor (CSTR) conditions, we discussed the attractors and Poincaré 1D maps with respect to flow rate as the control parameter. The new technique of the return maps from transient trajectories over the slow manifold is developed and applied in order to explore its multilayered structure related to dynamical states (periodic and aperiodic -chaotic oscillating modes) of the system. Kinetic relations underlying the slow manifold structure are briefly discussed.

Synergism and Physicochemical Properties of Anionic/Amphoteric Surfactant Mixtures with Nonionic Surfactant of Amine Oxide Type

The physicochemical properties of initial formulation, that is anionic/amphoteric surfactants mixture SLES/AOS/CAB (sodium lauryl ether sulfate (SLES), α-olefin sulfonates (AOS) and cocamidopropyl betaine (CAB) at ratio 80 : 15 : 5) with nonionic surfactant of amine oxide type (lauramine oxide (AO)) in various concentration (1–5%) were studied. To characterize the surfactants mixture, the critical micelle concentration (CMC), surface tension (γ), foam volume, biodegradability and irritability were determined. This study showed that adding of AO in those mixtures lowered both γ and CMC as well as enhanced SLES/AOS/CAB foaming properties, but did not significantly affect biodegradability and irritability of initial formulation. Moreover, an increase in AO concentration has a meaningful synergistic effect on the initial formulation properties. All those results indicates that a nonionic surfactant of amine oxide type significantly improves the performance of anionic/amphoteric mixed micelle systems, and because of that anionic/amphoteric/nonionic mixture can be used in considerably lower concentrations as a cleaning formulation.