Effect of the concentration of organic modifier in an aqueous-ethanol mobile phase on the chromatographic retention and thermodynamic characteristics of the adsorption of enantiomers of α-phenylcarboxylic acids on silica gel with immobilized eremomycin antibiotic

2014 ◽  
Vol 88 (10) ◽  
pp. 1778-1784 ◽  
Author(s):  
A. S. Blinov ◽  
E. N. Reshetova
Keyword(s):  
Silica Gel ◽  
Mobile Phase ◽  
Aqueous Ethanol ◽  
Thermodynamic Characteristics ◽  
Chromatographic Retention ◽  
Organic Modifier ◽  
Phenylcarboxylic Acids

Development of HPLC Method for the Purity Test by Design of Experiments and Determination of Activation Energy of Hydrolytic Degradation Reactions of Sofosbuvir

2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša
Keyword(s):  
Activation Energy ◽  
Design Of Experiments ◽  
Mobile Phase ◽  
Hydrolytic Degradation ◽  
Isoconversional Method ◽  
Hplc Method ◽  
Organic Modifier ◽  
Calculation Methods ◽  
Degradation Reactions

Background: The present study was focused on the development of HPLC method for purity testing of sofosbuvir by the Design of Experiments and determination of the activation energy of hydrolytic degradation reactions of sofosbuvir using HPLC based on the kinetics of sofosbuvir degradation. Methods: Following four factors for the Design of Experiments were selected, stationary phase, an organic modifier of the mobile phase, column temperature and pH of the mobile phase. These factors were examined in two or three level experimental design using Modde 11.0 (Umetrics) software. The chromatographic parameters like resolution, USP tailing and discrimination factor were calculated and analysed by partial least squares. The chromatography was performed based on Design of Experiments results with the mobile phase containing ammonium phosphate buffer pH 2.5 and methanol as an organic modifier. Separation was achieved using gradient elution on XBridge BEH C8 at 50 °C and a flow rate of 0.8 mL/min. UV detection was performed at 220 nm. The activation energy of hydrolytic degradation reactions of sofosbuvir was evaluated using two different calculation methods. The first method is based on the slope of dependence of natural logarithm of the rate constant on inverted thermodynamic temperature and the second approach is the isoconversional method. Results and Conclusion: Calculated activation energies were 77.9 ± 1.1 kJ/mol for the first method and 79.5 ± 3.2 kJ/mol for the isoconversional method. The results can be considered to be identical, therefore both calculation methods are suitable for the determination of the activation energy of degradation reactions.

scholarly journals Gradient HPLC in the determination of drug lipophilicity and acidity

2001 ◽  
Vol 73 (9) ◽  
pp. 1465-1475 ◽  
Author(s):  
Roman Kaliszan ◽  
Piotr Haber ◽  
Tomasz Baczek ◽  
Danuta Siluk
Keyword(s):  
Mobile Phase ◽  
High Performance ◽  
Standard Procedure ◽  
Gradient Elution ◽  
Log P ◽  
Retention Data ◽  
Organic Modifier ◽  
Wide Range ◽  
Aqueous Component ◽  
Initial Ph

The linear-solvent strength (LSS) model of gradient elution in high-performance liquid chromatography (HPLC) has been demonstrated to provide parameters of lipophilicity and acidity of analytes. pKa and log kw values are determined in three gradient runs. The first two experiments use an aqueous buffered eluent with a wide-range organic modifier gradient at pH of buffer, providing suppression of ionization of the analyte. That experiment allows an estimate of contents of the organic modifier in the mobile phase (%B), producing requested retention coefficient, k, for the nonionized form of the analyte. The next experiment is carried out with the latter %B and a pH-gradient of the aqueous component of the eluent that is sufficient to overlap possible pKa value of the analyte. The initial pH of the buffer used to make the mobile phase is selected to insure that the analyte is in nonionized form. The resulting retention time allows an estimate of pKa in a solvent of the given %B.The log kw parameter obtained correlated well with the corresponding value obtained by the standard procedure of extrapolation of retention data determined in a series of isocratic measurements. The correlation between log kw and the reference parameter of lipophilicity, log P, was very good for a series of test analytes. The values of pKa were found to correlate with the literature pKa data determined in water for a set of aniline derivatives studied.

The Presence of Disparlure, the Sex Pheromone of the Gypsy Moth, in the Female Nun Moth

1975 ◽  
Vol 30 (9-10) ◽  
pp. 672-675 ◽  
Author(s):  
B. A. Bierl ◽  
Morton Beroza ◽  
V. E. Adler ◽  
G. Kasang ◽  
D. Schneider ◽  
...  
Keyword(s):  
Sex Pheromone ◽  
Silver Nitrate ◽  
Silica Gel ◽  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Mass Spectra ◽  
Sex Attractant ◽  
Chromatographic Retention ◽  
Nun Moth ◽  
Physical And Chemical

Disparlure, (cis-7,8-epoxy-2-methyloctadecane) the sex attractant of the gypsy moth, Porthetria (Lymantria) dispar, attracts the male nun moth, Lymantria monacha, in the field and is a highly effective olfactory stimulus in electroantennogram (EAG) and single-cell recordings. We have now analyzed the extract of 2000 abdominal tips of the female nun moth. Physical and chemical tests, which included gas-chromatographic retention times, elution volumes from silica gel and silica gel-silver nitrate columns, mass spectra, epoxide functionality, EAG-activity of chromatographic fractions with gypsy moth antennae, presence of disparlure precursor, all indicated that disparlure is present in the extract of nun moth sex glands. The optical activity of the natural disparlure of the two species has not yet been determined. Several authors have reported 1-0 that disparlure,

Direct Reaction of Silica Gel with Butyllithium

2007 ◽  
Vol 2007 (9) ◽  
pp. 538-540
Author(s):  
Robert D. Guthrie
Keyword(s):  
Silica Gel ◽  
Silica Surface ◽  
Cold Water ◽  
Polar Compounds ◽  
Chromatographic Retention ◽  
Direct Reaction ◽  
Modified Silica Gel ◽  
Surface Areas ◽  
Butyl Group ◽  
Unmodified Silica

Silica gel with a variety of surface areas is found to react directly (no SOCl2 treatment required) with butyllithium to give a product with butyl groups attached. The extent of butyl group incorporation depends on available silica surface. With dehydrated 230–400 mesh silica gel, 7.4 mmoles of BuLi per g in pentane added in hexane gave silica with 2.5 mmoles of butyl groups per g provided that the silica gel was washed three times with cold water. It was found that water washing removes some unbutylated silicate increasing the apparent butyl group incorporation. The butyl-modified silica gel showed no chromatographic retention of 3-aminoquinoline in 50:50 hexane: dichloromethane or of thymol in hexane in contrast to unmodified silica gel which is known to strongly retain polar compounds, particularly basic ones. This contrast is demonstrated.

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