Lipophilicity characterization by reversed-phase liquid chromatography of some furan derivatives

Lipophilicity is one of the properties which influences the partition of a substance in biological media. The present study reports on the chromatographic behaviour of a newly synthesised series of furan derivatives by RP-HPLC and RP-TLC, with methanol-water and acetonitrile-water as mobile phases, in order to establish if the linear relationships between the retention parameters (log k, R(M)) and the concentration of organic modifier in the mobile phase, phi, allows the extrapolation procedure. Good correlations between the retention parameters were obtained by RP-HPLC and RP-TLC, and the concentration of organic modifier (methanol, acetonitrile) in the mobile phase was established for the studied furan derivatives. However, for the discussed compounds, acetonitrile has a lower sensitivity to changes in the structures. A good correspondence was obtained between the extrapolated parameters for the methanol-water mobile phase when using RP-HPLC and RP-TLC. However, stronger interactions occur in RP-TLC between the compounds and the residual silanol groups than in RP-HPLC.     

The influence of the structure of some aromatic heterocyclic derivatives on their retention in reversed-phase high-performance liquid chromatography

The chromatographic behavior of aromatic heterocyclic derivatives in reversed-phase high-performance liquid chromatography was investigated. The retention characteristics of the substances under the conditions of chromatography with water-acetonitrile mobile phases (retention factors, relative retentions, distribution coefficients, Henry adsorption constants, differences in the differential molar energy of sorption, and Gibbs energies of sorption) were determined. It was shown that the chromatographic retention of the sorbates depended on their molecular structure. The influence of the nature of heteroatoms and their number on the sorption of heterocyclic compounds was discussed. Original Russian Text ? S.V. Kurbatova, B.R. Saifutdinov, O.G. Larionov, V.V. Meshkovaya, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 3, pp. 557–564.     

The retention of some azoles in reversed-phase liquid chromatography

The influence of the structure-related physicochemical properties of derivatives of nitrogen-containing heterocyclic compounds on their retention under the conditions of reversed-phase liquid chromatography was studied. The dependence of the chromatographic retention of azole derivatives on the composition of the mobile phase was determined. The presence of azole protonated forms was substantiated by conductometric data.     

Prediction of peptides retention behavior in reversed-phase liquid chromatography based on their hydrophobicity

Hydrophobicity is an important physicochemical property of peptides and proteins. It is responsible for their conformational changes, stability, as well as various chemical intramolecular and intermolecular interactions. Enormous efforts have been invested to study the extent of hydrophobicity and how it could influence various biological processes, in addition to its crucial role in the separation and purification endeavor as well. Here, we have reviewed various studies that were carried out to determine the hydrophobicity starting from (i) simple amino acids solubility behavior, (ii) experimental approach that was undertaken in the reversed-phase liquid chromatography mode, and ending with (iii) some examples of more advanced computational and machine learning models.     

Separation of pyrimidine derivatives by reversed-phase high-performance liquid chromatography

Chromatographic behavior and separation conditions of pyrimidine derivatives were studied by high-performance liquid chromatography using a reversed-phase column and a multiwave UV detector.     

Comparative study of some commercial chemically bonded phases in classical reversed-phase chromatography and in ion-pair reversed-phase liquid chromatography

Summary The behaviour of various octadecyl commercial bonded phases are compared in classical reversed-phase chromatography and in ion-pair reversed-phase chromatography. Great differences are exhibited by the packings studied according to the polarity of the solutes. Whereas hydrocarbonaceous bonded phases show very similar selectivity versus apolar or weakly polar solutes, great differences are observed when analyzing more polar solutes even when ion-pair reversed-phase chromatography is performed.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Retention behavior of dipeptide isomers in reversed-phase high-performance liquid chromatography

Summary The effects of eluent pH and organic modifier concentration on the capacity factor (k) and selectivity of dipeptide isomers were investigated. It has been observed that the variation in the logarithm of the capacity factor of the dipeptide isomers is linearly dependent on the organic modifier concentration (C_b), however, the selectivity is almost independent of it. Both capacity factor and selectivity were seriously affected by the pH of the eluent. Both the capacity factor and the intercept of the ln k vs. C_b plot increased with increasing van der Waals volume of the non-polar amino acid subunit of the dipeptides.     

Separation of pantothenic acid derivatives by reversed-phase high-performance liquid chromatography

A variant of the use of reversed-phase high-performance liquid chromatography is described which permits the separation of pantothenic acid derivatives. The stationary phase used was a μBondapak-C₁₈ (4.1 × 250 mm column; 4.6 × 50 nm precolumn). Elution was performed in the isocratic regime using as mobile phase 20 M potassium phosphate buffer (pH 5.0)-methanol (91.5:8.5). The rate of elution was 1 ml/min. Retention times in the column for phosphopantothenate, pantothenate, phosphopantetheine, CoA, and dephosphoCoA were about 3.5, 6, 10.5, 16, and 42 min, respectively. This method, with radioactive detection, can be used for the analysis of pantothenic acid derivatives in liver extracts. One hour after white rats had been injected with [¹⁴C]pantothenic acid, the abovementioned components (with the exception of dephosphoCoA) contained the label in a ratio of 4:18:54:24. Institute of Biochemistry, Academy of Sciences of the Belorussian SSR, Grodno. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 855–858, November–December, 1988.     

Retention prediction of phenylthiohydantoin amino acid derivatives in reversed-phase liquid chromatography

Summary The concept of retention prediction for the separation of phenylthiohydatoin-amino acid derivatives in isocratic reversed-phase liquid chromatography is described. A novel retention-solubility parameter, R, is defined, for the retention prediction strategy and the performance of this R value is evaluated by comparing measured and predicted retention data. Excellent agreement between these values were observed. It is concluded that the R value has a very high potential in describing the retention of phenylthiohydantopinamino acid derivatives withdifferent types of separation systems consisting of C-18, C-8 and phenethyl bonded stationary phases and various mobile phases.     

Retention prediction of o-phthalaldehyde amino acid derivatives in reversed-phase liquid chromatography

Summary Retention prediction of o-phthalaldehyde amino acid derivatives in reversed-phase liquid chromatography has been investigated. The retention of all derivatives could be predicted within about 10% relative error under the appropriate separation conditions in both isocratic and gradient-elution modes.     

Separation of pantothenic acid derivatives by reversed-phase high-performance liquid chromatography

A variant of the use of reversed-phase high-performance liquid chromatography is described which permits the separation of pantothenic acid derivatives. The stationary phase used was a Bondapak-C₁₈ (4.1 × 250 mm column; 4.6 × 50 nm precolumn). Elution was performed in the isocratic regime using as mobile phase 20 M potassium phosphate buffer (pH 5.0)-methanol (91.5:8.5). The rate of elution was 1 ml/min. Retention times in the column for phosphopantothenate, pantothenate, phosphopantetheine, CoA, and dephosphoCoA were about 3.5, 6, 10.5, 16, and 42 min, respectively. This method, with radioactive detection, can be used for the analysis of pantothenic acid derivatives in liver extracts. One hour after white rats had been injected with [¹⁴C]pantothenic acid, the abovementioned components (with the exception of dephosphoCoA) contained the label in a ratio of 4:18:54:24.Institute of Biochemistry, Academy of Sciences of the Belorussian SSR, Grodno. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 855–858, November–December, 1988.     

Development of some stationary phases for reversed-phase high-performance liquid chromatography

The availability of a variety of stable organic stationary phases for columns has been a key factor in the development of HPLC as a major scientific tool. This paper explores the history and rationale used in the development of some important stationary phases and attempts to identify some of the strengths and limitations of these materials. Some of the author's experiences in stationary phase development illustrate approaches leading to present-day columns that exhibit a broad range of selectivity coupled with a high degree of reproducibility. Suggestions also are made for additional stationary phases that may be needed to complete column selectivity potential for HPLC separations.     

Quantitation of polyamines in cultured cells and tissue homogenates by reversed-phase high-performance liquid chromatography of their benzoyl derivatives

A rapid and simple method, originally described by Redmond and Tseng [J. Chromatogr., 170 (1979) 479] was applied to the analysis of di- and polyamines in cultured human tumour cells and human tumour xenografts. Optimization of the procedures and evaluation of the characteristic features of the assay are described. The (modified) procedure employs precolumn derivatization with benzoyl chloride, extraction of the derivatives by chloroform, separation by reversed-phase high-performance liquid chromatography under isocratic conditions and detection by ultraviolet absorbance measurement at 229 nm. The complete analysis was accomplished within 10 min per sample. The detection limit was ca. 1 pmol. The intra- and inter-assay coefficients of variation were 2.5-4.4% and 3.4-13.1%, respectively. The presence of well known inhibitors of polyamine biosynthesis, such as DL-alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone), did not interfere with the assay, and disturbance by cyclohexylamine could be avoided by changing the polarity of the mobile phase. The method proved to be very suitable because it is rapid, simple, requires a minimum of sample pretreatment, and still provides sufficient sensitivity to quantitate polyamines in relatively small amounts of cells (10(5) cells) or tumour tissues (less than 1 mg), even after treatment with inhibitors of polyamine biosynthesis.     

Unexpected behavior of digoxin at elevated temperatures in reversed-phase liquid chromatography

Summary Increased retention of digoxin has been observed at elevated temperatures on both 10 nm and 30 nm porediamter, RP-18 packing. This result is the opposite effect compared with the decreased retention under the same conditions with digoxin aglycon-digoxigenin. Rotation around the C−C σ-bonds in the digoxin molecule is presumed; the rod-like molecules of the newlyobtained digoxin penetrate stationary phase pores more easily thus increasing retention.     

The influence of the eluent composition on the retention of derivatives of some aromatic heterocyclic compounds in reversed-phase high-performance liquid chromatography

The influence of the composition of water-acetonitrile eluents on the retention of derivatives of aromatic heterocyclic compounds in reversed-phase high-performance liquid chromatography was studied. The coefficients of the displacement of acetonitrile molecules from the adsorption layer and equilibrium constants of quasi-chemical reactions of sorption and solvation of sorbate molecules were determined. For the investigated chromatographic systems, the applicability scope of the basic adsorption retention models are discussed. Original Russian Text ? S.V. Kurbatova, B.R. Saifutdinov, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 7, pp. 1377–1383.     

Reversed phase liquid chromatography of some benzimidazole derivatives

Summary The retention behaviour of a series of benzimidazole derivatives has been studied as a function of the water content of aqueous methanol and aqueous acetonitrile eluents. The relationship between the retention constant (log k) and the pH of the aqueous phase was linear, with slope values depending on the composition of the aqueous phase, the molecular structure of the compound, and the type of C-18 bonded stationary phase. The type of organic modifier significantly affected the shape of the relationship between log k and the volume fraction of organic modifier in the mobile phase.     

Determination of nitrophenol derivatives in various crops by reversed-phase ion-pair high-performance liquid chromatography

A method for the determination of nitrophenol derivatives in various crops and soil is described. The sample is extracted with dichloromethane; the extract is evaporated to dryness and the residue is dissolved in an alkaline methanol/water mixture. After filtration this solution is injected. The eluent contains methanol, water, a phosphate buffer and hexadecyltrimethylammonium as the pairing ion. Blank chromatograms for various crops do not show interfering peaks with detection at 365 or 405 nm. The limit of detection is usually around 0.01 mg kg^-1; recoveries generally exceed 80% (coefficient of variation, 5–10%). For 2,4-dinitrophenylthiocyanate and dinocap, recoveries are somewhat lower.     

The retention of selenium chains in reversed-phase liquid chromatography

Summary Organic polyselenides in which the selenium chains are terminated at both ends by ethyl-thio, butyl-thio, phenylthio, or phenyl groups were prepared. Their chromatographic behavior in HPLC on a bonded octadecyl phase with entirely or mainly methanolic eluents was investigated and compared with the corresponding polysulphides. The retention increment per Se atom is greater than that for S atoms. The ratio of Se to S increments is equal to the ratio of surface area increments. The S−Se bond does not have an appreciable influence on retention. Bonded to phenyl, selenium increases retention to the same extent as sulphur does. Some of the RSSe_nSR solutes were identified by mass spectrometry and other techniques.