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Abstract: A highly sensitive and selective thin layer chromatographic (TLC) method was developed for simultaneous determination of catecholamines and their related drugs using a new detection method and digital image processing of chromatographic plates. For the quantitative evaluation of the investigated compounds, the chromatographic separation was followed by spraying the plate with 0.02% solution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH ) in ethanol. The BioDit Thin Layer Chromatography (TLC) Scanner device and advanced specific software (ImageDecipher-TLC, Sorbfil TLC Videodensitometer and JustTLC) were used for the detection and quantification of chromatographic spots. For an accurate determination, the RGB colored images of the bright-white spots detected against a purple background were inverted and processed after their conversion into green scale. The results showed a strongly linear correlation between area (R 2>0.99) and volume (R 2>0.99) of spots and concentration of investigated compounds in all cases. The limit of detection (LOD) and the limit of quantification (LOQ) were below 49.3ng/spot and 69.6ng/spot respectively in all cases. The evaluation of the method was performed using different pharmaceutical samples spiked with the investigated amines and validated with respect to accuracy and precision. [Copyright &y& Elsevier]

Lafutidine (LTD) is a histamine H2 receptor antagonist, with anti-ulcer and mucosal protective activity. A sensitive and selective stability-indicating reversed- phase high-performance thin-layer chromatography (RP-HPTLC)/densitometry method is suggested for the determination of LTD in the presence of its acid, alkaline, oxidative and dry heat degradation products. Stress testing of LTD was done according to the International Conference on Harmonization (ICH) guidelines in order to validate the stability-indicating power of the analytical procedures. Stress testing demonstrated that LTD underwent acid, alkaline, oxidative and dry heat degradation; on the other hand, it showed stability towards neutral and photo degradation. Chromatography was performed on aluminum-backed silica gel 60 RP-18 F254 S plates with methanol:water:triethylamine 8:2:0.5 (v/v) as the mobile phase. Densitometric scanning was performed at 276 nm. The system gave compact bands for LTD (Rf 0.67±0.02). Linear regression analysis data for the calibration plots showed a good linear relationship with r² > 0.99 in the working concentration range 500 to 3000 ng per band. The limits of detection and quantification were 23.51 ng and 71.26 ng, respectively. The developed method can routinely be used for analysis of LTD in bulk and pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

The selected steroid compounds (androsterone, epi-androsterone, dehydroepi-androsterone, testosterone, stigmasterol, β-sitosterol, estradiol, hydrocortisone, and cholesterol) were investigated with the use reversed phase high performance thin layer chromatography on RP18W plates (#1.14296, E. Merck), using methanol-water, acetonitrile-water in different volume compositions as a mobile phases. The chromatographic parameters of lipophilicity (RMW) of the studied steroids were determined. Topological indexes based on the adjacency matrix: Gutman (M, Mν), Randic (oχν, 1χν, oχν, and 1χν), based on distance matrix: Rouvray (R), Wiener (W), and Pyka (A, oB, and 1B), and also based on information theory (ISA and ISA) and theoretical partition coefficients (Alog Ps, IAlog P, Clog P, log PKowwin, xlog P, and miLog P) for investigated steroids were calculated. It was found that lipophilicity determined chromatographically (RMW) correlated best with topological indices oχν, 1χν, R, W, A, and 1B. However, theoretical partition coefficient values (Alog Ps, IAlog P, Clog P, log PKowwin, xlog P, and miLog P) correlated best with topological index ISA. [ABSTRACT FROM AUTHOR]

Selected bile acids: cholic acid (C), glycocholic acid (GC), glycodeoxycholic acid (GDC), chenodeoxycholic acid (CDC), deoxycholic acid (DC), lithocholic acid (LC), and glycolithocholic acid (GLC) were investigated with the use of reversed phase high performance thin-layer chromatography on RP18W (E. Merck, #1.14296), RP18 (E. Merck, #1.05914), RP2 (E. Merck, #1.13726), and CNF 254 (E. Merck, #1.12571) plates using methanol–water, organic mixture (acetonitrile–methanol 50:50, v/v)–water, acetone–water, dioxane–water, and acetonitrile–phosphate buffer (pH 4.60) as mobile phases, in different volume compositions. The obtained separations were carried out on the basis of separation factors values ?R F and R S . None of the applied chromatographic conditions enabled completion of the separation of all examined bile acids. Five neighboring bile acids, i.e., LC/DC, CDC/GLC, GLC/C, C/GDC, GDC/GC, were separated only when CNF 254 plates and the mobile phase acetone–water, 50:50; v/v were used. The biggest problem was to separate DC from CDC. These bile acids were separated only on RP2 plates by using methanol–water, 65:35, v/v as a mobile phase. [ABSTRACT FROM AUTHOR]