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  • Author or Editor: Małgorzata Tatarczak x
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The chromatographic lipophilicity ( R M0 , ϕ 0 , S ) of eleven new 1,2,4-triazole derivatives has been determined by RP-TLC with methanol-water mobile phases containing sodium salts of the monovalent anions H 2 PO 4 , Cl , I , NO 3 , CF 3 COO , ClO 4 , and PF 6 . Addition of iodide anions to the mobile phase proved a key factor in obtaining lipophilicity indexes which correlated better with the log P G scale for all the solutes investigated. Addition of neutral or strong chaotropic salts (chlorides, hexafluorophosphates), according to the Hofmeister classification, improved the correlations between R M0 and S and between R M0 and ϕ 0 . Experimental log P TLC values were also established on the basis of calibration plots. These values were also correlated with the calculated lipophilicity log P G . Highly significant improvement of this correlation was achieved for mobile phases modified with sodium iodide. The results obtained are discussed in connection with the known physicochemical properties of anions in solution — lyotropic number, Jones-Dole B coefficient, entropy of hydration, surface tension increment, and effective anion polarizability.

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High-performance thin-layer chromatography (HPTLC) on silica gel 60 F 254 TLC plates, with ethyl acetate-methanol-acetone-acetic acid, 5 + 2 + 2 + 1, as mobile phase, has been used for simultaneous determination of rifampicin and isoniazid. Quantitative analysis was accomplished by UV-visible densitometric scanning.

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The retention behavior of amino acids on cellulose layers has been determined. With organic-aqueous mobile phases, linear second order relationships were established between volume fraction of organic solvent (tetrahydrofuran, acetonitrile, and 2-propanol) in water and retention, R M , for all the solutes investigated. The results obtained experimentally were compared with those calculated by use of polynomial and Soczewinski-Wachtmeister models of retention. Multiple development techniques (UMD and IMD) were also used. Predicted and experimentally obtained results were compared and assessed statistically. Chromatographic systems with the best separation selectivity were used for analysis of amino acids in reference solutions used for testing blood plasma.

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The purpose of this paper was to assess the suitability of thin-layer chromatography (TLC) as a pilot method for high-performance liquid chromatography (HPLC). The new 1,2,4-triazole and thiosemicarbazide derivatives were analyzed by use of reversed-phase (RP)-TLC and RP-HPLC techniques, applying octadecyl silica adsorbents and aqueous-organic mobile phases. Organic modifiers: methanol and acetonitrile were used at appropriate concentrations providing optimal retention factors. For both techniques, retention coefficient k in column chromatography and the retardation factor R F expressing retention in TLC were determined. The experimentally measured parameters were presented in a logarithmic scale as log k and R M, respectively. The constructed relationships between log k and R M allowed determining the possibility of TLC for anticipating HPLC retention behavior.

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We report the chromatographic behavior of the antitubercular drugs isoniazid (INH), pyrazinamide (PYR), ethambutol (ETB), and p -aminosalicylic acid (PAS) in reversed-phase TLC with organic aqueous mobile phases modified with Cu(II) chloride. The spectra of the free ligands and complexes formed during chromatography were measured densitometrically by use of a scanner equipped with a diode-array detector and compared in the range 200–700 nm. The complexes of Cu(II) with isoniazid and ethambutol were isolated on a micropreparative scale. The structures of the INH-Cu and EMB-Cu complexes were analyzed by electron paramagnetic resonance (EPR) spectroscopy and illustrated graphically by molecular modeling using GaussView software.

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