A contribution to evaluation of influence of medium in electronic and infrared spectroscopy

1982 ◽  
Vol 47 (4) ◽  
pp. 1060-1068 ◽  
Author(s):  
Vojtěch Bekárek ◽  
Jan Juřina
Keyword(s):  
Refractive Index ◽  
Infrared Spectroscopy ◽  
Correlation Coefficient ◽  
Solvent Effects ◽  
Electronic Spectra ◽  
Relative Permittivity ◽  
Solvent Parameters

Dependence of ET(30) of solvent parameters on relative permittivity (ε) and refractive index (n) of solvent has been found for forty solvents in the form ET(30)=29.87 + 72.03 (ε - 1/(2ε + 1)-29.16(ε - 1) (n 2 - 1)/(2ε + 1) (2n2 + 1), the correlation coefficient being 0.958. Relation has been discussed between ET(30) and π solvent parameters and significance of the term (ε - 1). (n2 - 1)/(2ε + 1) (2n2 + 1) has been tested for evaluation of solvent effects in electronic spectra.>

A test of the role of refractive index in correlations between solvent effects on electronic spectra and solvent effects on reaction equilibria and rates

1984 ◽  
Vol 49 (10) ◽  
pp. 2332-2341 ◽  
Author(s):  
Vojtěch Bekárek
Keyword(s):  
Refractive Index ◽  
Solvent Effects ◽  
Electronic Spectra ◽  
Kinetic Data ◽  
Fluorescence Spectra ◽  
Simple Relation ◽  
Absorption And Fluorescence Spectra ◽  
Induced Changes ◽  
Better Than

80 correlations have been carried out between the medium-induced changes in equilibrium and kinetic data (Y) and the medium-induced changes in positions of maxima in electronic (both absorption and fluorescence) spectra (Δν) of the Kamlet-Taft type indicators. The correlations have been carried out by means of the equations Y=Y0 + k . Δν and Y=Y0 + k' . Δν/f(n2) using only the Kamlet-Taft select solvents (SSS). The equation involving the function of refreactive index (n), f(n2) = (n2 - 1)/(2n2 + 1), is better than the simple relation between Y and Δν in 93% of the systems studied. The problem of HBD acidity of nitromethane and the relation of the A and B solvent characteristics by Swain and the characteristics of dipolarity of medium by Kamlet-Taft are discussed.

On the problem of empirical characteristics of a medium and their mutual relations

1983 ◽  
Vol 48 (5) ◽  
pp. 1237-1240 ◽  
Author(s):  
Vojtěch Bekárek ◽  
Marie Stolařová
Keyword(s):  
Free Energy ◽  
Refractive Index ◽  
Solvent Effects ◽  
Hyperfine Splitting ◽  
Ion Pairs ◽  
Life Time ◽  
Reaction Rates ◽  
Epr Spectra ◽  
Solvent Parameters ◽  
Mutual Relations

New parameters of polarity, acidity, and basicity of a medium, which are more suitable to characterize nonspectral solvent effects, were derived by dividing the Taft-Kamlet solvent parameters π*, α, and β by a function of the refractive index n, f(n) = (n2 - 1)/(2n2 + 1). The new parameters were used in evaluating the effect of the medium on reaction rates, equilibria, solubilities, hyperfine splitting constants in EPR spectra, fluorescence life time, free energy of dissolution of ions and ion pairs, and on the Snyder solvent factors of the elution strength in chromatography.

Measurement of the Ratio of Tea Polyphenols to Amino Acids in Green Tea Infusion Based on near Infrared Spectroscopy

2011 ◽  
Vol 301-303 ◽  
pp. 1093-1097 ◽  
Author(s):  
Shi Rong Ai ◽  
Rui Mei Wu ◽  
Lin Yuan Yan ◽  
Yan Hong Wu
Keyword(s):  
Amino Acids ◽  
Infrared Spectroscopy ◽  
Correlation Coefficient ◽  
Green Tea ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Tea Polyphenols ◽  
Strong Absorption ◽  
Tea Infusion

This study attempted the feasibility to determine the ratio of tea polyphenols to amino acids in green tea infusion using near infrared (NIR) spectroscopy combined with synergy interval PLS (siPLS) algorithms. First, SNV was used to preprocess the original spectra of tea infusion; then, siPLS was used to select the efficient spectra regions from the preprocessed spectra. Experimental results showed that the spectra regions [7 8 18] were selected, which were out of the strong absorption of H2O. The optimal PLS model was developed with the selected regions when 6 PCs components were contained. The RMSEP value was equal to 0.316 and the correlation coefficient (R) was equal to 0.8727 in prediction set. The results demonstrated that NIR can be successfully used to determinate the ration of tea polyphenols to amino acids in green tea infusion.

scholarly journals The Kinetic Model of the Peel Brittleness of Stored Cucumis Melons Based on Visible/Near-Infrared Spectroscopy

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Defang Xu ◽  
Huamin Zhao ◽  
Shujuan Zhang ◽  
Chengji Li ◽  
Fei Zhao
Keyword(s):  
Infrared Spectroscopy ◽  
Kinetic Model ◽  
Correlation Coefficient ◽  
Root Mean Square ◽  
Near Infrared Spectroscopy ◽  
Storage Time ◽  
Near Infrared ◽  
Mean Square ◽  
Zero Order Reaction ◽  
Variation Tendency

A kinetic model based on visible/near-infrared spectroscopy of the peel brittleness of “Xintian-125” Cucumis melons, the research object, stored under room temperature, was established in order to realize real-time monitoring of the peel brittleness of Cucumis melons and for prediction of storage time. The NIR and peel brittleness of melons stored for 1, 4, and 7 days were collected and measured. SG was confirmed to be the best pretreatment by comparing the PLS models established with 4 pretreatment methods, and the differences of the prediction set determination coefficient and root-mean-square were 0.818 and 23.755, respectively. CARS and SPA were adopted to extract the feature wavelengths and establish the peel brittleness of PLS prediction model. The model’s prediction accuracy was 0.919, and the prediction root-mean-square was 25.413, indicating that NIR is able to realize the prediction of the peel brittleness of Cucumis melons. As a result, a NIR-based peel brittleness kinetic model was created. The P value of the regression model was less than 0.001, and the model’s correlation coefficient was 0.8503, showing that the model is of extreme significance and high precision. The zero-order reaction equation was overfitted according to the variation tendency of the average peel brittleness of stored melons. The model’s correlation coefficient was 0.981, the standard error was 4.624, and the linear relation between the stored period and NIR was established based on it. The research proves that the NIR-based technology is able to realize quick and loss-free inspection of melons’ peel brittleness and prediction of the stored period.

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