Kinetic studies on the peroxyoxalate chemiluminescence reaction: determination of the cyclization rate constant

Luminescence ◽  
2002 ◽  
Vol 17 (5) ◽  
pp. 313-320 ◽  
Author(s):  
Sandra M. Silva ◽  
F�lvio Casallanovo ◽  
Karen H. Oyamaguchi ◽  
Luiz F. L. M. Ciscato ◽  
Cassius V. Stevani ◽  
...  
Keyword(s):  
Rate Constant ◽  
Kinetic Studies ◽  
Peroxyoxalate Chemiluminescence ◽  
Cyclization Rate

Stability Indicating Liquid Chromatographic Method for the Determination of Fenofibrate and its Application to Kinetic Studies

2013 ◽  
Vol 5 (4) ◽  
pp. 1866-1874
Author(s):  
K. Srinivasa Rao ◽  
Keshar N K ◽  
N Jena ◽  
M.E.B Rao ◽  
A K Patnaik
Keyword(s):  
Degradation Products ◽  
Kinetic Studies ◽  
Pharmaceutical Formulations ◽  
Assay Method ◽  
Pharmaceutical Dosage Form ◽  
Stability Indicating ◽  
Zero Order Kinetics ◽  
Relative Standard ◽  
Liquid Chromatographic

A stability-indicating LC assay method was developed for the quantitative determination of fenofibrate (FFB) in pharmaceutical dosage form in the presence of its degradation products and kinetic determinations were evaluated in acidic, alkaline and peroxide degradation conditions. Chromatographic separation was achieved by use of Zorbax C18 column (250 × 4.0 mm, 5 μm). The mobile phase was established by mixing phosphate buffer (pH adjusted 3 with phosphoric acid) and acetonitrile (30:70 v/v). FFB degraded in acidic, alkaline and hydrogen peroxide conditions, while it was more stable in thermal and photolytic conditions. The described method was linear over a range of 1.0-500 μg/ml for determination of FFB (r= 0.9999). The precision was demonstrated by relative standard deviation (RSD) of intra-day (RSD= 0.56– 0.91) and inter-day studies (RSD= 1.47). The mean recovery was found to be 100.01%. The acid and alkaline degradations of FFB in 1M HCl and 1M NaOH solutions showed an apparent zero-order kinetics with rate constants 0.0736 and 0.0698  min−1 respectively and the peroxide degradation with 5% H2O2 demonstrated an apparent first-order kinetics with rate constant k = 0.0202 per min. The t1/2, t90   values are also determined for all the kinetic studies. The developed method was found to be simple, specific, robust, linear, precise, and accurate for the determination of FFB in pharmaceutical formulations.  

Determination of rate constants of redox reactions of second order from current-less potential-time curves by a simplified graphical-numerical method

1983 ◽  
Vol 48 (5) ◽  
pp. 1358-1367 ◽  
Author(s):  
Antonín Tockstein ◽  
František Skopal
Keyword(s):  
Numerical Method ◽  
Explicit Form ◽  
Rate Constant ◽  
Optimization Algorithm ◽  
Rate Constants ◽  
Redox Reactions ◽  
Second Order ◽  
Wide Region ◽  
Recurrent Formula

A method for constructing curves is proposed that are linear in a wide region and from whose slopes it is possible to determine the rate constant, if a parameter, θ, is calculated numerically from a rapidly converging recurrent formula or from its explicit form. The values of rate constants and parameter θ thus simply found are compared with those found by an optimization algorithm on a computer; the deviations do not exceed ±10%.

Regeneration Mechanism Studied by Potential-Time Response to Sinusoidal Current-Time Function

1997 ◽  
Vol 62 (10) ◽  
pp. 1511-1526
Author(s):  
María-Luisa Alcaraz ◽  
Ángela Molina
Keyword(s):  
Kinetic Parameters ◽  
Rate Constant ◽  
Theoretical Study ◽  
Time Function ◽  
Time Response ◽  
Current Time ◽  
Regeneration Mechanism ◽  
Sinusoidal Current ◽  
Regeneration Processes

A theoretical study of the potential-time response to sinusoidal current applied to static and dynamic electrodes for regeneration processes is presented. Methods for determination of the regeneration fraction, rate constant of the chemical reaction and heterogeneous kinetic parameters are proposed.

scholarly journals Lifetime predictions of non-ionic and ionic biopolymers: kinetic studies by non-isothermal thermogravimetric analysis

2021 ◽  
Author(s):  
Martina Maria Calvino ◽  
Lorenzo Lisuzzo ◽  
Giuseppe Cavallaro ◽  
Giuseppe Lazzara ◽  
Stefana Milioto
Keyword(s):  
Degradation Kinetics ◽  
Kinetic Studies ◽  
Ionic Polymers ◽  
Heating Rates ◽  
Exponential Factor ◽  
Master Plot ◽  
Plot Analysis ◽  
Sustainable Polymers ◽  
Master Plot Analysis

AbstractIn this paper, films based on sustainable polymers with variable charge have been investigated by non-isothermal thermogravimetry in order to predict their lifetime, which is a key parameter for their potential use in numerous technological and biomedical applications. Specifically, chitosan has been selected as positively charged biopolymer, while alginate has been chosen as negatively charged biopolymer. Among non-ionic polymers, methylcellulose has been investigated. Thermogravimetric measurements at variable heating rates (5, 10, 15 and 20 °C min−1) have been performed for all the polymers to study their degradation kinetics by using isoconversional procedures combined with ‘Master plot’ analyses. Both integral (KAS and Starink methods) and differential (Friedman method) isoconversional procedures have shown that chitosan possesses the highest energetic barrier to decomposition. Based on the Master plot analysis, the decomposition of ionic polymers can be described by the R2 kinetic model (contracted cylindrical geometry), while the degradation of methylcellulose reflects the D2 mechanism (two-dimensional diffusion). The determination of both the decomposition mechanism and the kinetic parameters (activation energy and pre-exponential factor) has been used to determine the decay time functions of the several biopolymers. The obtained insights can be helpful for the development of durable films based on sustainable polymers with variable electrostatic characteristics. Graphical abstract

Direct determination of the rate constant for the reaction CO + N2O → CO2 + N2

1985 ◽  
Vol 122 (5) ◽  
pp. 489-492 ◽  
Author(s):  
Nobuyuki Fujii ◽  
Tomohisa Kakuda ◽  
Takeo Sugiyama ◽  
Hajime Miyama
Keyword(s):  
Rate Constant ◽  
Direct Determination

scholarly journals Micellar Electrokinetic Chromatographic Study of the Separation of an Aromatase Inhibitor and a Tryciclic Antidepressant in the Breast Cancer Treatment

2008 ◽  
Vol 3 ◽  
pp. ACI.S939 ◽  
Author(s):  
J. Rodríguez Flores ◽  
A.M. Contento Salcedo ◽  
L. Muñoz Fernández
Keyword(s):  
Micellar Electrokinetic Chromatography ◽  
Solid Phase ◽  
Background Electrolyte ◽  
Kinetic Studies ◽  
Breast Cancer Treatment ◽  
Chromatographic Study ◽  
Optimal Conditions ◽  
Sodium Dodecylsulphate ◽  
Experimental Parameters

Micellar electrokinetic chromatography (MEKC) was investigated for the simultaneous determination of letrozole, imipramine and their metabolites in human urine samples over a concentration range of therapeutic interest. Experimental parameters such as pH of the running electrolyte, sodium dodecylsulphate (SDS) concentration, borate concentration, voltage, etc were investigated. Under optimal conditions of 25 mM SDS, 15 mM borate buffer (pH 9.2), 15% 2-propanol, as background electrolyte; 28 kV and 40 °C, as voltage and cartridge temperature, respectively; resolution between the peaks was greater than 1.7. Before the determination, a solid phase extraction (SPE) procedure with a C18 cartridge was optimized. Good linearity, accuracy, precision, robustness and ruggedness were achieved and detection limits of 12.5 ng/mL for letrozole and its metabolite and 37.5 ng/mL, were obtained for imipramine and their metabolites. Real determinations of these analytes in two patient urines were carried out. Sensitivity achieved in this method is sufficient to perform kinetic studies in humans.

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