scholarly journals Two-Dimensional Correlation Analysis in Application to a Kinetic Model of Parallel Reactions

2003 ◽  
Vol 57 (2) ◽  
pp. 168-175 ◽  
Author(s):  
Thou-Long Chin ◽  
King-Chuen Lin
Keyword(s):  
Kinetic Model ◽  
Correlation Analysis ◽  
Absorption Coefficient ◽  
Rate Constant ◽  
Reference Spectrum ◽  
Two Dimensional ◽  
Constant Intensity ◽  
Increase With Increase ◽  
Parallel Reactions ◽  
Coherence Spectrum

By applying generalized two-dimensional (2D) correlation analysis as reported by Noda, we have systematically studied a kinetic model of parallel reactions. Given the related rate constants and absorption coefficients, the correlation between reactant and products are analyzed. The reactant–reactant, reactant–product, and product–product pairs are found to be synchronously correlated, and their intensities increase with increase of the rate constant and the absorption coefficient. On the other hand, only the reactant–product pairs show in the asynchronous spectra. Their intensities also depend proportionally on the rate constant and the absorption coefficient. The influence of signal-to-noise ratio (S/N) and overlapped spectra are further discussed. The resulting synchronous and asynchronous correlation spectra for the kinetic model appear to be weakly influenced by poor quality of the signal when the reference spectrum is set at zero. The ratio of asynchronous to synchronous correlation intensity yields a coherence spectrum. This spectrum remains a constant intensity for all the correlated peaks, being free from the influence of rate constant and absorption coefficient as well as being weakly disturbed by a small S/N ratio. It also provides a way to evaluate the extent of spectral overlap between two peaks. The coherence spectrum is useful to characterize the type of parallel reactions.

Two-Dimensional Correlation Spectroscopy: Effect of Reference Spectrum on Noise-Free and Noisy Spectra

2003 ◽  
Vol 57 (8) ◽  
pp. 991-995 ◽  
Author(s):  
Mirosław A. Czarnecki
Keyword(s):  
Correlation Analysis ◽  
Correlation Spectroscopy ◽  
The Other ◽  
Reference Spectrum ◽  
Two Dimensional ◽  
Data Set ◽  
Noise Effect ◽  
Contour Plots ◽  
Selection Of ◽  
2D Correlation Analysis

It has been shown that for two-dimensional (2D) correlation analysis with a perturbation average, the first or the last spectrum in the data set as a reference provides identical qualitative results. On the other hand, selection of the reference spectrum significantly different from the spectra used for 2D correlation analysis may complicate interpretation of the contour plots and in consequence lead to erroneous results. The effect of noise is relatively small when 2D correlation spectra are calculated without the reference spectrum. For the other reference spectra the magnitude of the noise effect is comparable. In all cases, the asynchronous spectra are more strongly affected by the noise as compared to the synchronous spectra.

Kinetic-Model-Free Analysis of Transient Absorption Spectra Enabled by 2D Correlation Analysis

2021 ◽  
pp. 4148-4153
Author(s):  
Julian Hniopek ◽  
Carolin Müller ◽  
Thomas Bocklitz ◽  
Michael Schmitt ◽  
Benjamin Dietzek ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Correlation Analysis ◽  
Absorption Spectra ◽  
Transient Absorption ◽  
Transient Absorption Spectra ◽  
Model Free ◽  
2D Correlation Analysis

scholarly journals A Novel Stoichio-Kinetic Model for the DPPH• Assay: The Importance of the Side Reaction and Application to Complex Mixtures

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1019
Author(s):  
Lucrezia Angeli ◽  
Sebastian Imperiale ◽  
Yubin Ding ◽  
Matteo Scampicchio ◽  
Ksenia Morozova
Keyword(s):  
Antioxidant Activity ◽  
Kinetic Model ◽  
Rate Constant ◽  
High Resolution Mass Spectrometry ◽  
Sinapic Acid ◽  
Side Reaction ◽  
Main Reaction ◽  
Dpph Assay ◽  
Best Fitting ◽  
The Common

The 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assay is widely used to determine the antioxidant activity of food products and extracts. However, the common DPPH• protocol uses a two-point measurement and does not give information about the kinetics of the reaction. A novel stoichio-kinetic model applied in this study monitors the consumption of DPPH• by common antioxidants following the second order reaction. The fitting of such decay yields the rate constant k1, which describes the main reaction between antioxidants and DPPH•, and the rate constant k2, which is attributed to a slower side reaction considering the products generated between the transient radicals (AO•) and another molecule of DPPH•. The model was first applied to antioxidant standards. Sinapic acid, Trolox and ascorbic and chlorogenic acids did not show any side reaction. Instead gallic, ferulic and caffeic acids achieved the best fitting with k2. The products of the side reaction for these compounds were confirmed and identified with high-resolution mass spectrometry. Finally, the kinetic model was applied to evaluate the antioxidant activity of eight herbal extracts. This study suggests a new kinetic approach to standardize the common DPPH• assay for the determination of antioxidant activity.

THEORETICAL MODEL FOR THE CALCULATION OF OPTICAL PROPERTIES OF GOLD NANOPARTICLES

2010 ◽  
Vol 19 (03) ◽  
pp. 427-436
Author(s):  
A. MENDOZA-GARCÍA ◽  
A. ROMERO-DEPABLOS ◽  
M. A. ORTEGA ◽  
J. L. PAZ ◽  
L. ECHEVARRÍA
Keyword(s):  
Gold Nanoparticles ◽  
Refractive Index ◽  
Optical Properties ◽  
Theoretical Model ◽  
Absorption Coefficient ◽  
Molecular System ◽  
Two Dimensional ◽  
Box Models ◽  
Solvent Environment ◽  
Absorption And Dispersion

We have developed an analytical method to describe the optical properties of nanoparticles, whose results are in agreement with the observed experimental behavior according to the size of the nanoparticle under analysis. Our considerations to describe plasmonic absorption and dispersion are based on the combination of the two-level molecular system and the two-dimensional quantum box models. Employing the optical stochastic Bloch equations, we have determined the system's coherence, from which we have calculated expressions for the absorption coefficient and refractive index. The innovation of this methodology is that it allows us to take into account the solvent environment, which induce quantum effects not considered by classical treatments.

scholarly journals Central Composite Design, Kinetic Model, Thermodynamics, and Chemical Composition of Pomelo (Citrus Maxima (Burm.) Merr.) Essential Oil Extraction by Steam Distillation

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2075
Author(s):  
Tan Phat Dao ◽  
Thanh Viet Nguyen ◽  
Thi Yen Nhi Tran ◽  
Xuan Tien Le ◽  
Ton Nu Thuy An ◽  
...  
Keyword(s):  
Activation Energy ◽  
Kinetic Model ◽  
Essential Oil ◽  
Rate Constant ◽  
Flow Rate ◽  
Steam Distillation ◽  
Extraction Process ◽  
Oil Extraction ◽  
Extraction Time ◽  
Pomelo Peel

Pomelo peel-derived essential oils have been gaining popularity due to greater demand for stress relief therapy or hair care therapy. In this study, we first performed optimization of parameters in the pomelo essential oil extraction process on a pilot scale to gain better insights for application in larger scale production. Then extraction kinetics, activation energy, thermodynamics, and essential oil quality during the extraction process were investigated during the steam distillation process. Three experimental conditions including material mass, steam flow rate, and extraction time were taken into consideration in response surface methodology (RSM) optimization. The optimal conditions were found as follows: sample weight of 422 g for one distillation batch, steam flow rate of 2.16 mL/min and extraction time of 106 min with the coefficient of determination R2 of 0.9812. The nonlinear kinetics demonstrated the compatibility of the kinetic model with simultaneous washing and unhindered diffusion with a washing rate constant of 0.1515 min−1 and a diffusion rate constant of 0.0236 min−1. The activation energy of the washing and diffusion process was 167.43 kJ.mol−1 and 96.25 kJ.mol−1, respectively. The thermodynamic value obtained at the ΔG° value was −35.02 kJ.mol−1. The quality of pomelo peel essential oil obtained by steam distillation was characterized by its high limonene content (96.996%), determined by GC-MS.

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