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A thin-layer chromatographic and densitometric method has been developed for the identification and quantitation of gliclazide and its impurities on silica gel, using chloroform–methanol, 19 + 1 (v/v), as mobile phase. UV densitometric measurements were made at λ = 226 nm. The method is characterized by high sensitivity (15 ng), linearity over a wide concentration range (0.06 to 0.30 mg mL 1), and high recovery (100.23%). It was found that the established conditions can be also used for determination of impurities in medicines.

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Molecular interactions have been evaluated in liquid adsorption chromatography with mixed mobile phases. Two equations based on different retention mechanism models were verified experimentally. The parameters of both equations were calculated and interpreted. The parameters described the association phenomenon in analyzed systems. Solvation effects were taken into account. These effects were confirmed by use of two independent theories and two independent equations. The equation parameters were calculated for test substances in four chromatographic systems in which solvation phenomenon was present or not. A linear relationship was found between parameters analyzed. Chromatographic measurements were obtained by use of thin-layer chromatography.

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This report describes the TLC separation of two classes of chiral drug, including β-blocking drugs and non-steroidal anti-inflammatory drugs (NSAID) on molecularly imprinted chiral stationary phases, in the same way as has been performed by HPLC. Several molecularly imprinted polymers (MIP) were prepared using the enantiomers of either the β-blocking drugs, R-(+)-propranolol, R-(+)- or S-(–)-atenolol, or the NSAID, S-(+)-naproxen and S-(+)-ibuprofen, as print molecules. Three different functional monomers, ITA, MAA, and VPD were employed in the imprinting process. The polymers prepared in the presence of MAA or VPD could be coated as thin layers on glass supports, but not those prepared in the presence of ITA. The MIP of R-(+)-propranolol, with 5% acetic acid in acetonitrile as mobile phase, resolved the racemate of propranolol into two spots, but tailing spots were obtained. The MIP prepared from S-(+)-naproxen, with 1% acetic acid in THF–heptane, 1 + 1, as mobile phase, resolved the racemate of ketoprofen into enantiomers, with a good separation factor (α = 5.2).

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Gradient thin-layer chromatography and densitometry have been used for qualitative and quantitative analysis of caffeic acid in some Dipsacaceae family plants. The presence of caffeic acid was determined in complex plant extracts before and after acid hydrolysis.

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By use of pH 6.0 acetate buffer a mixture of Chelidonium majus L. alkaloids has been separated, on a classical silica column, into two groups, tertiary and quaternary alkaloids. The relationships between R F and the concentration of methanol in the acetate buffer suggested it was possible, by gradient elution in which the concentration of methanol in the pH 6.0 aqueous acetate buffer was increased, to separate the quaternary alkaloids further into fractions containing 2 or 3 alkaloids. These fractions were then separated by micropreparative zonal thin-layer chromatography. Sanguinarine and chelerithrine of high purity were obtained.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Joerg Stroka, Thomas Peschel, Günther Tittelbach, Gerhard Weidner, Robert van Otterdijk, and Elke Anklam

A computer-driven office scanner has been modified to enable measurement of the fluorescence of aflatoxins on thin-layer chromatography (TLC) plates. The main modifications were substitution of the light tube with a black light tube and inclusion of a filter. The strategy behind this modification, and its problems, are discussed. The modified scanner can be used to determine aflatoxins at low nanogram levels, which, when used in combination with an appropriate TLC method, enables monitoring of the compounds in food and feed at the levels stipulated in European legislation.

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The chromatographic behavior of calix[4]arene, 4-tert-butylcalix[4]arene tribenzoate, 4-tert-butylcalix[5]arene, and pyrene have been studied. Chromatography was performed on K-60 and RP-18 wettable with water TLC and HPTLC plates under isothermal conditions (303 K). Methanol, ethanol, and acetonitrile and their binary mixtures with water were used as mobile phases. The ranges of mobile-phase compositions in which retardation factor (R F) values were equal to zero were wider for alcohol–water mixtures than for acetonitrile–water mixtures. Plots of R M against the mole fraction of acetonitrile in water (0.19 ≤ X S ≤ 1.00) were linear for all the solutes investigated. The best separation of the calixarenes was obtained by use acetonitrile–water mobile phases and RP18W plates.

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Levels of formaldehyde, formed within the cells of plants, animals, and man, are related to the physiological state of an organism. We have previously reported the possibility of determining the formaldehyde content of human teeth in some physiological states, and it was established that the level of HCHO in carietic teeth is higher than in healthy teeth. The aim of the work described in this paper was the OPLC determination of HCHO levels in teeth suffering from eight different rare pathological disorders. It was shown that significantly different levels of formaldehyde were present in teeth in different pathological states. The highest HCHO content was observed in teeth with acute inflammatory changes. The lowest level was found in teeth with no inflammatory changes.

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