Kinetics of the Bray-Liebhafsky oscillatory reaction perturbed by polymer supported cobalt catalyst

The Bray-Liebhafsky (BL) oscillatory reaction generated in the batch reactor at 62- 68 oC was perturbed by cobalt(II)-nitrate, supported on the macroreticular copolymer of poly-4-vinylpyridine with divinylbenzene (Co-PVPDVB). The kinetic data was analyzed of the complex pathways of the hydrogen peroxide decomposition in the examined BL reaction. The obtained results confirm that the kinetics of the BL reaction in the presence Co-PVPDVB comes partially from the Co-catalyst and partially from the macroreticular copolymer support.Oscilatorna reakcija Bray-Liebhafsky (BL) realizovana u zatvorenom reaktoru na temperaturi 62-68 oC je perturbovana sa kobalt(II)nitratom ugrađenim na makroretikularnom kopolimeru poli-4-vinilpiridina sa divinilbenzenom (Co- PVPDVB). Analizirani su kinetički podaci kompleksnih reakcionih puteva razlaganja vodonikperoksida u ispitivanoj BL reakciji. Dobijeni rezultati potvrđuju da je u prisustvu Co-PVPDVB kinetika BL reakcije delimično određena Co-katalizatorom, a delimično makromolekularnim kopolimernim nosačem katalizatora

Analytical applications of oscillatory chemical reactions: determination of some pharmaceuticaly and biologically important compounds

Novel analytical methods for quantitive determination of analytes based on perturbations of oscillatory chemical reactions realized under open reactor conditions (continuosly fed well stirred tank reactor, CSTR), have been developed in the past twenty years. The proposed kinetic methods are generally based on the ability of the analyzed substances to change the kinetics of the chemical reactions matrix. The unambiguous correlation of quantitative characteristics of perturbations, and the amount (concentration) of analyte expressed as a regression equation, or its graphics (calibration curve), enable the determination of the unknown analyte concentration. Attention is given to the development of these methods because of their simple experimental procedures, broad range of linear regression ( 10-7 10-4 mol L-1) and low limits of detection of analytes ( 10-6 10-8 mol L1, in some cases even lower than 10-12 mol L-1). Therefore, their application is very convenient for routine analysis of various inorganic and organic compounds as well as gases. This review summarizes progress made in the past 5 years on quantitative determination of pharmaceutically and biologically important compounds

Dynamic states of the Bray-Liebhafsky reaction when sulfuric acid is the control parameter

Dynamic behavior of hydrogen peroxide decomposition catalyzed by iodate and hydrogen ions (the Bray-Liebhafsky reaction), in a continuous stirred tank reactor is investigated. The experimental results are obtained at one operational point in concentration phase space by varying mixed inflow concentrations of the sulfuric acid. The experimental evidences for the onset and termination of oscillatory behavior via the saddle node infinite period bifurcation as well as some kind of the Andronov-Hopf bifurcation are presented. In addition, the possibility of excitability of a stable steady state by thiamine was observed

Activity of polymer supported cobalt catalyst in the Bray-Liebhafsky oscillator

The infuence of poly-4-vinylpyridine-co-divinylbenzene-Co2+ catalyst on the Bray-Liebhafsky (BL) oscillator used as the matrix for establishing catalyst's activity was analyzed. The addition of the catalyst do not change the dynamics of the reaction in the BL matrix, but the periods of the oscillatory evolution as well as the preoscillatory period (tau(1)) and the duration from the beginning of the reaction to the end of the oscillatory state (tau(end)). All experimental results are simulated satisfactory

Quantitative Determination of Some Water-Soluble B Vitamins by Kinetic Analytical Method Based on the Perturbation of an Oscillatory Reaction

A novel procedure for kinetic determination of some water-soluble vitamins of the B-group (thiamine (B-1), riboflavin (B-2), niacin (B-3) and pyridoxine (B-6)) by the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory chemical system involving the catalytic decomposition of hydrogen peroxide in the presence of both hydrogen and iodate ions is proposed and validated. The method uses a Pt electrode for potentiometric monitoring of the concentration perturbations of the BL matrix in a stable non-equilibrium stationary state close to the bifurcation point. The proposed method relies on the linear relationship between maximal potential displacements, Delta E-m, caused by the additional known quantities of a B species. Under the optimal established analytical conditions, linear calibration curves were obtained over the range of 0.01-1.0, 0.016-0.128, 5.0-50.0 and 0.05-2.5 mu mol with the limits of detection of 0.01, 0.018, 2.6 and 0.03 mu mol, as well as analytical throughput of 30, 5, 12 and 20 determinations per hour, for B-1, B-2, B-3 and B-6, respectively. The used technical approach also provides simple, effective and convenient method to assay the pharmaceutical formulations containing B-1 together with other active principles such as nicotinamide and vitamin B-12 as well as B-3

Doprinos razvoju nove mikrozapreminske/mikro-koncentracione kvantitativne analize - određivanje morfina

The results of investigation of a new kinetic analytical method for microquantitative (microconcentration/microvolume) determination of morphine is given. This method is based on potentiometric monitoring of the concentration perturbations of the Bray-Liebhafsky reaction as the oscillatory reaction system being in a stable non-equilibrium stationary state close to a bifurcation point. The experiments are carried out in an open reactor at T=310 K. The response of the matrix system to perturbations by different concentrations of morphine ethanolic solutions is followed by a Pt-electrode. In the concentration range from 0.11 to 2.90 μg mL-1 (3.14´10-7 - 7.65´10-6 mol dm-3) of morphine, a linear response of the maximal potential shift versus the logarithm concentrations of morphine is found. The average relative standard deviation of morphine determination in 5% ethanol solution is 5,4%. The detection limit of the morphine concentration is 41 ng mL-1. The accuracy of the method is 98.5%. The method is simple, reliable and cheap.Daju se rezultati istraživanja nove kinetičke metode mikrozapreminskog/mikrokoncentracionog određivanja morfina. Ona se zasniva na potenciometrijskom praćenju odgovora analitičke matrice - nelinearnog reakcionog sistema Bray-Liebhafsky u neravnotežnom stacionarnom stanju u blizini bifurkacione tačke na impulsne perturbacije različitim količinama alkoholnog rastvora alkaloida morfina. U uslovima korišćene izotermalne (T=310 K) analitičke matrice, koja je realizovana u protočnom dobromešajućem reaktoru, promena potencijala Pt-oksidoredukcione elektrode izazvana perturbacijom sa morfinom u odnosu na potencijal koji karakteriše neravnotežno stacionarno stanje neperturbovane analitičke matrice, pokazuje linearnu zavisnost od logaritma količine morfina u području od 0,11-2,90 μg mL-1 (3,14x10-7 do 7,65x10-6 mol dm-3) morfina. Pri tome je srednja relativna standardna devijacija određivanja morfina u 5% alkoholnom rastvoru 5,4%, detekcioni limit 41 ng mL-1, a tačnost 98,5%. Metoda je jednostavna pouzdana i jeftina

Determination of critical micelle concentration of cetyltrimethylammonium bromide: Different procedures for analysis of experimental data

Conductivity of two micellar systems was measured in order to determine critical micelle concentration (CMC) of cetyltrimethylammonium bromide (CTAB). Those systems were: CTin water and CTin binary mixture acetonitrile (ACN)-water. Conductivity (κ)-concentration (c) data were treated by four different methods: conventional method, differential methods (first and second derivative) and method of integration (methods A-D, respectively). As CTin water micellar system shows a sharp transition between premicellar and postmicellar part of the κ/c curve, any of the applied methods gives reliable CMC values and there is no statistically significant difference between them. However, for CTin ACN-water mixture micellar system the integration method for CMC determination is recommended due to a weak curvature of κ/c plot

Kinetic determination of morphine by means of Bray-Liebhafsky oscillatory reaction system using analyte pulse perturbation technique

A novel kinetic method for micro-quantitative determinations of morphine (MH) is proposed and validated. The method is based on the potentiometric monitoring of the concentration perturbations of the oscillatory reaction system being in a stable non-equilibrium stationary state close to the bifurcation point between stable and oscillatory state. The response of the Bray-Liebhafsky (BL) oscillatory reaction as a matrix system, to the perturbations by different concentrations of morphine, is followed by a Pt-electrode. The proposed method relies on the linear relationship between maximal potential shift, Delta E-m, and the logarithm of the added morphine amounts in the range of 0.004-0.18 mu mol. Under optimum conditions, the sensitivity of the proposed method (as the limit of detection) is 0.001 mu mol and the method is featured by good precision (R.S.D. = 1.6%) as well as the excellent sample throughput (45 samples h(-1)). In addition to standard solution analysis, this approach was successfully applied for quantitative determination of morphine in a typical pharmaceutical dosage form. Some aspects of the possible mechanism of morphine action on the BL oscillating chemical system are discussed in detail

Performance and Efficiency of Anionic Dishwashing Liquids with Amphoteric and Nonionic Surfactants

Performance and efficiency of anionic [sodium lauryl ether sulfate (SLES) and sodium alpha-olefin sulfonate (AOS)] and amphoteric [cocamidopropyl betaine (CAB)] as well as nonionic [cocodiethanol amide (DEA), various ethoxylated alcohols (C-12-C-15-7EO, C-10-7EO and C-9-C-11-7EO) and lauramine oxide (AO)] surfactants in various dishwashing liquid mixed micelle systems have been studied at different temperatures (17.0, 23.0 and 42.0 degrees C). The investigated parameters were critical micelle concentration (CMC), surface tension (gamma), cleaning performance and, foaming, biodegradability and irritability of anionic (SLES/AOS) and anionic/amphoteric/nonionic (SLES/AOS/CAB/AO) as well as anionic/nonionic (SLES/AOS/DEA/AO, SLES/AOS/C-12-C-15-7EO/AO, SLES/AOS/C-10-7EO/AO and SLES/AOS/C-9-C-11-7EO/AO) dishwashing surfactant mixtures. In comparison to the starting binary SLES/AOS surfactant mixture, addition of various nonionic surfactants promoted CMC and gamma lowering, enhanced cleaning performance and foaming, but did not significantly affect biodegradability and irritability of dishwashing formulations. The anionic/nonionic formulation SLES/AOS/C-9-C-11-7EO/AO shows both the lowest CMC and gamma as well as the best cleaning performance, compared to the other examined dishwashing formulations. However, the results in this study reveal that synergistic behavior of anionic/nonionic SLES/AOS/ethoxylated alcohols/AO formulations significantly improves dishwashing performance and efficiency at both low and regular dishwashing temperatures (17.0 and 42.0 degrees C) and lead to better application properties