Proc. 9th Internat. Symp. Instr. Chromatogr., Interlaken, April 9.-11., 251-259 (1997). General aspects of quality assurance and validation in connection with TLC and the Camag Video Documentation System (including schematic presentation, flow chart of the validation procedure and a chromatogram of a caffeine standard obtained from the CCD image of the HPTLC).

J. Planar Chromatogr. 28, 241-247 (2015). TLC of (1) citicoline sodium in the presence of its (2) alkaline degradation products in pharmaceutical oral solution on silica gel with ammonia - ethyl acetate - triethylamine 12:7:1. Quantitative determination by absorbance measurement at 272 nm. The hRF value was 35 for (1) and 10 for (2). Linearity for (1) was between 0.6 and 2.2 µg/zone. The intraday precision was 0.2 % and interday precision was 1.2 % for (1). The LOD and LOD of (1) were 41 ng/zone and 237 ng/zone, respectively.

J. Planar Chromatogr. 10, 290-297 (1997). TLC of miltefosine on silica with chloroform - ethanol - p-toluenesulfonic acid (0.25 mol/L) in NH3 25% 7:4:1. Detection by immersion into a copper(II) sulfate solution (10 g copper sulfate were filled up to 100 mL with 8% phosphoric acid) for a few seconds and heated at 180°C for 20 min. Quantification by densitometry at 500 nm. For detection of 1-octadecanol development in dichloromethane - methanol - 25% NH3 (100:1:0.2), followed by immersion into copper sulfate solution. Validation, specificity, linearity, accuracy, detection and quantification limit, precision, robustness, log P determination, method development, experimental details, and results are described in detail. Also published in Proc. 9th Internat. Symp. Instr. Chromatogr., Interlaken, April 9.-11., 289-303 (1997).

J. Planar Chromatogr. 28, 426-435 (2015). HPTLC of methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate and butyl 4-hydroxybenzoate on silica gel with petroleum ether - acetic acid 20:3. Quantitative determination by absorbance measurement at 254 nm. The influence of experimental settings on densitometric evaluation using the TLC Scanner 4 was investigated to assess the impact on signal intensities, peak shape/resolution and quantitative results. Peak positions can shift for up to 0.5 mm for fast scan speeds. For improved quantitative results the scan slit length should be set to 75 % of the band length, the scan speed to 5 or 10 mm/s and data resolution to 25 or 50 μm/step. The resolution mode of the optical system provided higher signal intensities compared to the light mode. Peak broadening was observed for higher scan speeds, whereby the signal height decreased significantly, if compared to the peak area evaluations. The effects of the instrumental settings on the signal intensity were less pronounced for the evaluations via peak area. Hence, peak area evaluations were more robust with regard to the changed settings.

Proc. 9th Internat. Symp. Instr. Chromatogr., Interlaken, April 9.-11., 365-372 (1997). Presentation of the validation of a HPTLC procedure for quantification of caffeine with a Video Documentation System. Validation was performed according to the ICH guidelines, considering the special features of the method. The validation parameters were: selectivity, stability of the analyte, linearity, precision (repeatability and intermediate precision) and robustness. The obtained results were compared with those obtained by the slit-scanning densitometer. HPTLC of caffeine on silica with dichloromethane - methanol 9:1. Evaluation by densitometry at 270 nm. Repeatability 1.59% (densitometer) and 1.21% (CCD camera); intermediate precision 1.22% (densitometer) and 1.12% (CCD camera); robustness 1.47% (densitometer) and 1.37% (CCD camera).

Trends Anal. Chem. 81, 51-62 (2016). Review on aspects to consider during calibration for quantitative chromatographic analysis such as noise and detector response, data acquisition and processing, calibration curve and inverse calibration.

Determination of isoniazid in serum by thin-layer chromatography.) (Chinese). J. Pharm. Anal. (Yaowu Fenxi Zazhi) 17, 116-118 (1997). TLC on silica with chloroform - methanol 9:1. In situ spectra recording of isoniazid and its salicylaldehyde - and benzaldehyde-derivatives. Quantification by densitometry at 225 nm. Validation of the method by investigation of linearity and range, RSD, recovery and detection limits for the compounds.

J. Chromatogr. A 1477, 108-113 (2016). In order to study the kinetics of invertase, a specific fructofuranosidase was cloned from the Leishmania major genome. Determination of the kinetic parameters of the β-D-fructofuranosidase by TLC on silica gel impregnated with sodium bisulfate and citrate, developed successively twice with acetonitrile – water 4:1. Detection of the three carbohydrates sucrose, glucose and fructose by dipping the plates in a solution of 4-aminobenzoic acid. Quantitative determination by UV-densitometry. Description of the hydrolysis of sucrose by the Michaelis-Menten kinetic parameters (KM, Vmax) equal to 63.1 ± 7.6 mM, 0.04 ± 0.001 mM/min using glucose production and 83.0 ± 14.4 mM, 0.03 ± 0.002 mM/min monitoring fructose. Also, comparison of hydrolyses of three alternative substrates, raffinose, stachyose and inulin, and characterization of the regiospecificity of the reaction. The method proved to be suitable for the refined kinetic analysis of different reactions related to the hydrolysis of sugars.