S. M. Petrović

High-performance liquid chromatography of some digitalis glycosides and their aglycones on chemically bonded phases

Abstract The retention behaviour of some glycosides their aglycones was studied as a function of the composition of the acetonitrile—water eluent. The relationship between the retention constant (log k′) and the volume fraction of acetonitrile in the eluent was parabolic and of shape indicating a “dual” retention mechanism for all solutes studied. This behaviour is discussed in terms of the nature of the solute, eluent and stationary phase.

Utilization of the functional group contribution concept in liquid chromatography on chemically bonded reversed phases

The possibilities of utilizing the UNIFAC group model of activity coefficients for the prediction of reversed-phase liquid chromatographic retention data are discussed. Provided that the retention of a solute i is due to liquid—liquid partition, the retention constant (ln ki) is related to the activity coefficient of the solute in the mobile phase (ln γim) by ln ki = ln γim + constant. By comparison of experimentally observed ki and calculated γim values, it is shown that for certain solutes the UNIFAC concept can be used for the calculation of changes in solute retention with alterations in mobile phase composition, and for a rough estimation of absolute retention indices. By correlating ki and γim values, it is possible to calculate the phase ratio of the chromatographic system and the activity coefficient of a solute in the stationary phase.

Correlation between retention and the C18 silica surface coverage in reversed-phase liquid chromatography

SummaryMembers of three homologous series and five non-homologous solutes with various functional groups were chromatographed on a series of well-characterized C18 reversed stationary phases with a range of methanol-water mobile phases. Measured capacity factors of solutes were correlated with the concentration of C18 ligands on the stationary phase. A linear relationship with the slope depending on a solute molecular structure and the volume fraction of methanol in the mobile phase was obtained. A method for the evaluation of phase ratio is also proposed.

Effect of pH on the acid hydrolysis of Jerusalem artichoke inulin

Abstract The effect of pH on the simultaneous dehydration of fructose and hydrolysis of the Jerusalem artichoke inulin was investigated. Between pH 1 and 2 the extent of dehydration of fructose varied linearly with time and pH but was minimal at pH 2. The complete hydrolysis of the Jerusalem artichoke inulin was therefore attained at pH 2 after 2·5 h and at 100°C with minimum fructose dehydration.

HPLC behavior and hydrophobic parameters of some anilides

SummaryThe chromatographic behavior ofpara substituted anilides of 2,2-dimethylpropanoic, benzoic and α-phenyl acetic acid has been studied by reversed-phase high performance liquid chromatography. HPLC was performed on a C-18 column with various aqueous methanol mobile phases. The influence on the retention of anilide type and additional substituents in the molecule is discussed.Several chromatographic hydrophobicity parameters (CHP) have been calculated by linear correlation between logk of the investigated compounds and the concentration of methanol in the mobile phase. The chromatographic hydrophobicity parameters were compared with the logP values calculated by Rekkers fragmental method. The results show moderate correlations of CHP with logP. Thus, multiple linear regressions have been applied. It was found that besides logP even the electronic effects of individual polar groups capable of hydrogen bonding proced to be very important in hydrophobic characterization of the molecule.

High-performance liquid chromatography of some estrogens on chemically bonded phases

SummaryThe chromatographic behaviour of 30 estradiol and estrone derivatives has been studied on diol, amino- and cyanopropyl silica gel stationary phases with non-aqueous mobile phases. The slopes of linear relationships between the logarithm of the retention factor and logarithm of the volume fractions of the polar components of the binary eluents have been calculated and are discussed in relation to the characteristics of the solute, eluent and stationary phase. An equation for testing the separation efficiency of stationary phases has been derived.

Reversed phase liquid chromatography of some benzimidazole derivatives

SummaryThe 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.

Thin-layer chromatography of metal ions on a new carbamide-formaldehyde polymer

SummaryA number of metal ions were systematically chromatographed on thin-layer of a newly synthesized carbamide-formaldehyde polymer using neutral and acidic eluents. For comparison, metal ions were also chromatographed on cellulose layers with the same eluents.

Retention behaviour and molecular structure of the solute in thin-layer chromatography

SummaryDual retention behaviour on cellulose, silica and alumina in thin-layer chromatography, that is, the separation of solutes either in normal phase or in reversed phase mode is discussed as a function of the mobile phase polarity utilizing the solubility parameter theory and then correlated with the molecular structure of the solute.

Thin-layer chromatography of benzamides on cellulose and unconventional starch and aminoplast supports

SummaryThe retention behaviour and separation ability of cellulose, starch and aminoplast thin-layers with aqueous and non-aqueous mobile phases has been studied by measuring the retention of a homologous series of benzamides. The retention behaviour and separation ability are discussed in terms of the nature of the solute, support and eluent.