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In this study, in order to evaluate the quality and safety of selected commercial spices brands, contents of moisture and minerals, as well as the concentration of certain heavy metals (As, Hg and Pb) were determined in oregano, sweet basil, parsley and celery. The spice samples were subjected to microwave digestion, and were analyzed by atomic absorption spectrometry (AAS), using hydride generation AAS technique, cold vapor AAS technique, and graphite furnace AAS technique for determination of As, Hg and Pb, respectively. Maximum concentrations of As and Pb were determined in the same brand sample of celery, and are 0.75 ppm and 0.40 ppm, respectively, while the maximum concentration of Hg in various brands sweet basil samples is 0.05 ppm. According to the results, the contents of moisture and minerals, as well as the concentrations of heavy metals in all selected spices were below the maximum permissible limits declared by the national legislations, and are safe for human consumption. [Projekat Ministarstva nauke Republike Srbije, br. 172015]

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.

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. [ABSTRACT FROM AUTHOR]

Perturbation of the BrayLiebhafsky non-oscillating subsystem (mixture of KIO3 and H2SO4), i.e., Dushman reaction ( DR), by piroxicam (PX), was observed in an open reactor, i.e., in the continuously fed well-stirred tank reactor (CSTR). Monitoring the response of DR to perturbations by different concentrations of PX allows developing a simple procedure for quantitative determination of this analyte in both bulk drug and pharmaceutical preparation (injection). A tentative perturbation mechanism of PX action on the DR matrix, based on a kinetic scheme that was suggested by Agreda et al., is proposed. The PX reactivity in DR has been generally related to the reaction of PX with hypoiodous acid (HIO) present in the matrix. [ABSTRACT FROM AUTHOR]

The influence of the initial malonic acid concentration [MA]0 (8.00 x 10(-3) < or = [MA]0 < or = 4.30 x 10(-2) mol dm(-3)) in the presence of bromate (6.20 x 10(-2) mol dm(-3)), bromide (1.50 x 10(-5) mol dm(-3)), sulfuric acid (1.00 mol dm(-3)) and cerium sulfate (2.50 x 10(-3) mol dm(-3)) on the dynamics and the kinetics of the Belousov-Zhabotinsky (BZ) reactions was examined under batch conditions at 30.0 degrees C. The kinetics of the BZ reaction was analyzed by the earlier proposed method convenient for the examinations of the oscillatory reactions. In the defined region of parameters where oscillograms with only large-amplitude relaxation oscillations appeared, the pseudo-first order of the overall malonic acid decomposition with a corresponding rate constant of 2.14 x 10(-2) min(-1) was established. The numerical results on the dynamics and kinetics of the BZ reaction, carried out by the known skeleton model including the Br2O species, were in good agreement with the experimental ones. The already found saddle node infinite period (SNIPER) bifurcation point in transition from a stable quasi-steady state to periodic orbits and vice versa is confirmed by both experimental and numerical investigations of the system under consideration. Namely, the large-amplitude relaxation oscillations with increasing periods between oscillations in approaching the bifurcation points at the beginning and the end of the oscillatory domain, together with excitability of the stable quasi-steady states in their vicinity are obtained.