- Part 1. Fundamentals of systematic quantitative errors. J. Planar Chromatogr. 18, 51-56 (2005). First part of a series covering systematic errors arising in separation systems, evaluation and calibration errors, nonlinear separation and quantitation techniques, the sf4-procedure for finding total systematic errors, systematic errors caused by regulations, and conclusions and proposals for quantitative planar liquid chromatography (PLC). 1) Nonsystematic errors: 1.1 Finding systematic errors hidden in nonsystematic errors, 1.2 Are random errors unstable? 1.3 Errors caused by (false) statements. 2) The main sources of systematic errors in quantitative PLC: 2.1 Chromatography, 2.2 Physics (baseline - baseplane; practical example). 2.3 Mathematics (detectability limit of the systematic error and the standard certainty STC). 3) Sampling chromatography.

J. Planar Chromatogr. 18, 364-367 (2005). HPTLC of ephedrine on silica gel in a presaturated twin-trough chamber with toluene - diethyl acetate - diethylamine 7:2:1. Quantitative determination by absorbance measurement at 200 nm. Also HPTLC of methanolic extracts of roots and aerial parts of different Sida species with toluene - chloroform - ethanol 13:30:7. Common and distinguishing bands were observed.

J. Planar Chromatogr. 18, 61-66 (2005). TLC of three antidiabetic agents (pioglitazone, rosiglitazone, and repaglinide) on silica gel RP-8 with buffer - organic modifier binary mobile phases of widely different compositon in horizontal chambers; visualization under UV light at 254 nm. Peak-purity tests by recording the in-situ spectra in the wavelength range of 200 to 400 nm.

J. Planar Chromatogr. 18, 326-329 (2005). HPTLC of levonorgestrel on silica gel (prewashed with chloroform - methanol 1:1 and once with the mobile phase, dried and activated at 100 °C for 15 min) with toluene - 2-propanol 9:1 in an automatic multiple development chamber without chamber saturation. Visual examination under UV light at 254 nm; quantitation by densitometry at 250 nm.

J. Chromatogr. B 823 (2), 152-157 (2005). HPTLC of lamotrigine (extracted from serum by ethyl acetate) on silica with toluene - acetone - ammonia 14:6:1. Densitometric measurement at 312 nm, hRf of lamotrigine at 54. The analytical method has excellent linearity (r = 0.998) in the range of 20–300 ng/spot. This assay range is adequate for analyzing human serum, as it corresponds to lamotrigine concentrations measured in human serum from epileptic patients. The method was validated for sensitivity, selectivity, extraction efficiency, accuracy and intra and inter-day reproducibility. The limit of detection and limit of quantification were found to be 6.4 and 10.2 ng, respectively. Good accuracy and high precision (CV) is reported, i.e. in the range of 92.1-97.1 % and 0.5-2.6 % respectively. The method was applied for determination of serum lamotrigine levels in epileptic patients and in pharmacokinetic study of lamotrigine administered orally to rabbits.

leaf powder by high-performance thin-layer chromatography. J. Planar Chromatogr. 18, 305-307 (2005). HPTLC of methanolic extracts of Cinnnamomum tamala leaves and eugenol on silica gel with toluene - ethyl acetate - formic acid 90:10:0.1. Detection and quantitation by densitometry at 280 nm.

whole-plant powder by High-Performance Thin-layer Chromatography. J. Planar Chromatogr. 19, 68-72 (2006). HPTLC of oleanolic acid on silica gel with dichloromethane - toluene - acetone - methanol 30:40:15:3. Detection by spraying with Liebermann-Burchard reagent; quantification by densitometry at 529 nm. Detection and quantitation limits were 0.1 µg and 0.5 µg, respectively. Oleanolic acid response was linear over the range 1 to 9 µg. The validated HPTLC method can be used for routine quality-control analysis of Oldenlandia corymbosa L. whole-plant powder and for quantitative determination of oleanolic acid.

Indian Drugs 42 (8), 511-515 (2005). HPTLC carvedilol in tablets on silica gel with toluene - methanol - ethyl acetate - ammonia 40:10:5:1. Quantitative determination by absorbance measurement at 254 nm. The method was linear in the range of 50-250 µg/µL with recovery of 98.5-100.2 %. Stability was studied during and after development. Accuracy, precision, and specificity of the method were established.