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The chromatographic behavior of some phenolic compounds has been studied with the objective of understanding the role of cyano groups in the processes of chromatographic separation on thin layers of CN-silica gel. For this purpose separations were performed on thin layers of CN-silica gel, unmodified silica gel, and polyacrylonitrile adsorbent (PANS) using fourteen mobile phases, nine of which resulted in normal-phase systems. On the basis of the results obtained the effect of compound structure (i.e. properties of ortho substituents of the compounds separated) on their retention is discussed. The dependence of the order of retention of the phenols on the properties of the adsorbent was also considered. Plots of retention data ( R M against R M ) determined by use of different chromatographic systems were used to characterize the systems used. The results enabled hypotheses to be formulated about possible mechanisms involved in the separations of the phenols on these adsorbents.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors:
Mirjana Aleksić
,
Jadranka Odović
,
Dušanka Milojković-Opsenica
, and
Živoslav Tešić

The chromatographic behavior of five myorelaxant drugs has been studied under the conditions used for salting-out thin-layer chromatography (SOTLC) on cellulose and alumina. For this purpose, aqueous ammonium sulfate solutions of different concentration were used as mobile phases. It was established that hR F values always decreased in parallel to increasing salt concentrations. When cellulose was used as adsorbent, a linear relationship was observed between the R M values and the ammonium sulfate content of the mobile phase. Regression data of the plots obtained were used to determine the lipophilicity parameters R M 0 and C 0 . Lipophilicity determined in this way correlated with calculated log P values.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors:
Dušanka Milojković-Opsenica
,
Kristina Lazarević
,
Vojkan Ivačković
, and
Živoslav Tešić

The chromatographic behavior of nine frequently used water-soluble food dyes has been studied by TLC on RP-18 silica gel. Reversed-phase chromatographic separations were performed with mobile phases containing ammonium sulfate and water with ethanol or acetone as organic modifiers. The effect of mobile phase composition on retention, and the selectivity of the chromatographic systems, are discussed, and on the basis of the results obtained separation mechanisms are proposed. It was established that ammonium sulfate as a component of the mobile phase significantly increased the reversed-phase behavior of the chromatographic systems used.

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The behavior of five ACE inhibitors and their active degradation products in salting-out thin-layer chromatography (SO TLC) has been examined on silica gel, cellulose, and polyacrylonitrile (PAN) with aqueous ammonium sulfate solutions of different concentration as mobile phases. It was found that increasing the concentration of the salt in the mobile phase led to increased R M values for all the substances. Linear relationships were established between salt concentration and R M values and regression data of the plots obtained were used to determine the lipophilicity R M 0 and C 0 . Lipophilicity determined in this way was correlated with calculated log P values. For comparison of these results with chromatographic behavior in conventional RP TLC, the examined substances were subjected to thin-layer chromatography on RP-18 silica gel with methanol-water mobile phases.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors:
Jelena Veličković
,
Deana Andrić
,
Goran Roglić
,
Živoslav Tešić
, and
Dušanka Milojković-Opsenica

The chromatographic behavior of fourteen 1-arylpiperazine derivatives has been studied by thin-layer chromatography on both silica gel and RP-18 silica gel. Unmodified silica gel was used as polar stationary phase in combination with monocomponent and binary non-polar mobile phases. Binary mobile phases comprising mixtures of methanol, acetone, or dioxane (as organic modifiers) and water were used with RP-18 silica for studies of the chromatographic behavior of the compounds under reversed-phase conditions. An approximately linear relationship was obtained between R M values and the amount of organic modifier in the mobile phases employed. The effect of mobile phase composition on the retention of the substances is discussed, as is the selectivity of the chromatographic systems used. Separation mechanisms are proposed on the basis of the results obtained.

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Experimental R M values for a series of functionalized 2-alkylidene-4-oxothiazolidines and 1,2-dithioles have been determined by reversed-phase TLC on RP-18 silica plates. Binary mixtures of methanol and water, tetrahydrofuran and water, and acetone and water were used as mobile phases. R M 0 values were determined for these mobile phase mixtures by linear extrapolation to 0% ( v/v ) organic modifier. The lipophilicity, C 0 , was calculated as the ratio of the intercept and slope values. Chromatographically obtained lipophilicity data correlated well with calculated log P values.

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Experimental R M values for two series of β-diketonato complexes, M(acac) 3- n (phacphac) n and M(acac) 3- n (phSacphSac) n , where M represents cobalt(III) or chromium(III), have been determined by reversed-phase thin-layer chromatography on RP-18 silica with binary tetrahydrofuran-water, acetonitrile-water, and acetone-water mobile phases. R M 0 values were determined for the different mobile phase mixtures by linear extrapolation to 0% ( v/v ) organic modifier. Lipophilicity C 0 was calculated as the ratio of the intercept and slope values. Chromatographically obtained lipophilicity was correlated with calculated C log P values.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors:
Tomislav Tosti
,
Katica Drljević
,
Dušanka Milojković-Opsenica
, and
Živoslav Tešić

The chromatographic behavior of roxithromycin, midecamycin, erythromycin, azithromycin, and erythromycin ethylsuccinate has been studied by salting-out thin-layer chromatography (SOTLC) with cellulose as a adsorbent and aqueous ammonium sulfate solutions of different concentration as mobile phases. Hydrophobicity was determined from the linear relationships between solute R M values and the ammonium sulfate content of the mobile phase. Hydrophobicity values R M 0 and C 0 were calculated on the basis of the results obtained. Lipophilicity determined in this way was correlated with calculated log P values.

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An overview of the adsorption characteristics of 3-cyanopropylsiloxane-bonded silica gel as a specific, moderately polar sorbent which can be used for separation of different classes of organic and inorganic substances in both normal- and reversed-phase chromatography is presented. The most important separation mechanisms that govern the retention on this sorbent are underlined. In addition, some recently published applications of 3-cyanopropylsiloxane-bonded silica gel as a sorbent in thin-layer chromatography are listed.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors:
Tomislav Tosti
,
Gordana Rakić
,
Maja Natić
,
Dušanka Milojković-Opsenica
,
Suren Husinec
,
Vladimir Savić
, and
Živoslav Tešić

The chromatographic behavior of three biocidal technical materials, rodenticide active ingredients brodifacoum, bromadiolone, and coumatetralyl, and impurities present in the technical material was investigated by both normal-phase (NP) and reversed-phase (RP) planar chromatography. The research was carried out using thinlayers of silica gel, alumina, cellulose, and C 18 silica. Several solvents on their own or in various combinations and proportions were used for separation. The optimum chromatographic systems for separation of the substances from each other and from their impurities were selected. Under reversed-phase chromatographic (RPC) conditions a linear correlation between R M values and mobile phase composition was established. From results obtained, the lipophilicity R M ° and C 0 were determined. Possible separation mechanisms are discussed on the basis of the established retention behavior.

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