62nd Indian Pharmaceutical Congress Abstract No. F-384 (2010). TLC of isotretinoin on silica gel with toluene – ethyl acetate 4:1. The hRf value was 54. Quantitative determination by absorbance measurement at 345 nm. The method was linear in the range of 20-100 ng/band. The sample was analysed by RP-HPLC and the result was comparable with the TLC method.

European Journal of Medicinal Chemistry 45, 3719-3725 (2010). TLC of sulpiride and mebeverine hydrochloride on silica gel with absolute ethanol - methylene chloride - triethylamine 35:15:1. Quantitative determination by absorbance measurement at 221 nm. The method was linear in the range of 0.4-1.4 µg/band for sulpiride and 0.2-1.6 µg/band for mebeverine hydrochloride. The recovery was 100.4-101.0 %. The hRf value of sulpiride was 42 and of mebeverine hydrochloride 62. The results obtained by this TLC method were comparable with those by HPLC.

J. of Chromatogr. A 1248, 169-177 (2012). Purified oligomers of hyalobiuronic acid are indispensable tools to elucidate the physiological and pathophysiological role of hyaluronan degradation by various hyaluronidase isoenzymes. Establishment and validation of a novel sensitive, convenient, rapid, and cost-effective HPTLC method for the qualitative and quantitative analysis of small saturated hyaluronan oligosaccharides consisting of 2–4 hyalobiuronic acid moieties. HPTLC on amino phase with 1-butanol - formic acid - water 3:5:2 or 3:4:1. Detection 1) by spraying with orcinol in various concentrations of sulfuric acid; 2) by dipping into the reagent of orcinol in 10 % sulfuric acid and Morgan–Elson reagent; 3) by illuminating with white light and UV 366 nm after heating. The simple reagent-free in situ derivatization of 3) resulted in a detection limit of 7–19 pmol/band and LOQ of 37–71 pmol/band depending on the analyzed saturated oligosaccharide. Identification of the analytes by TLC-ESI-MS. The validated HPTLC method, as an alternative to sequential techniques such as HPLC and CE, can easily be automated and is applicable to the analysis of multiple samples in parallel.

CBS 108, 12-15 (2012). HPTLC of anthracene (ANT), benzo[b]fluoranthene (BBF), benzo[k]fluoranthene (BKF), pyrene (PYR), acenaphthene (ACE), benzo[a]anthracene (BAA), benzo[a]pyrene (BAP), benzo[ghi]perylene (BPE), chrysene (CHR), dibenzo[a,h]anthracene (DBA), indeno[1,2,3-c,d]pyrene (IND), fuorene(FLU), fuoranthene (FLA), and phenanthrene (PHE) in toys on RP-18 phase with acetonitrile - water 9:1 by three-fold development over 45, 55 and 65 mm using automated multiple development (AMD) under nitrogen. Detection at 254 and 366 nm. Quantitative fluorescence measurement at different excitation wavelengths with cut-off filters: 220 nm/>320 nm for ACE, 250/>320 for ANT, 366/>400 for BAA and BAP, 270/>400 for BBF, BPE, BKF, CHR, DBA, FLA, IDN (after dipping in nitromethane), 250/>320 for FLU and PHE and at 270/>320 for PYR. Polynomial regression with high coefficients of correlation and low standard deviations. Coeffivients of variation for repeatability and reproducibility were below 10 %. This method allows the determination of 14 of the 16 PAHs. With LODs of 0.1-0.2 mg/kg the demands for the German GS mark (label for checked safety) are fulfilled. The results by HPTLC were comparable to results obtained by GC-MS.

J. of Chromatogr. A 1281, 135-141 (2013). The use of detergents for the extraction, solubilization and purification of membrane proteins (MPs) is necessary due to their hydrophobic nature. Detergent quantification is essential to routine analysis because the concentration of amphiphiles is crucial in the crystallization process. HPTLC of detergents (in small quantities, bound to solubilized MPs) on silica gel with dichloromethane – methanol – acetic acid 80:19:1. The optimum HPTLC conditions were investigated using n-dodecyl-beta-D-maltoside (DDM), the most popular detergent for membrane protein crystallization. Quantification by fluorescence measurement at 366 nm using a Hg lamp. The calibration curve was linear in the range of 100-1600 ng of DDM in water and the limit of detection of was 50 ng/zone, which is the best LOD achieved to date for a routine detergent assay (not modified by the addition of NaCl, commonly used in protein buffers). In comparison with other techniques (colorimetry, GC, and FTIR) the HPTLC method has the advantage of no prior sample treatment for concentration or extraction, and no chemical labeling is required. In comparison with TLC, the HPTLC method is 100 times more sensitive. The HPTLC method is suitable for routine analysis, assay results are obtained within 3 hours and only few microliters of sample are needed.

J. Planar Chromatogr. 28, 126-132 (2015). TLC of 17 morphine derivatives on RP phase with 3 different mobile phases, (1) methanol - 0.02 M ammonium hydroxide, (2) methanol - 0.7 M ammonium hydroxide, and (3) methanol - 0.02 M acetic acid. In each case, the individual mobile phases contained 30-90 % (v/v; in 10 % increments) of methanol as an organic modifier. Detection by absorbance measurement at 254 nm. RP-TLC can be used for the characterization of the lipophilicity of semisynthetic derivatives of morphine.

J. Chromatogr. Sci. 54 (5), 842-846 (2016). Development of a new chromatographic method for direct enantioresolution of (RS)-baclofen by ligand-exchange TLC, adopting two different approaches: (A) on plates prepared by mixing the ligand exchange reagents (LER) with silica gel slurry, development with different achiral solvents or solvents without chiral additive; (B) on silica gel without chiral selector and the LER consisting of Cu(II)–L-amino acid complex as chiral mobile phase additive. Preparation of LERs by using Cu(II) acetate and four L-amino acids (L-tryptophan, L-histidine, L-proline and L-phenylalanine). Detection by exposure to iodine vapor. Study of the effect of temperature and the mole ratio of Cu(II)-to-amino acid on enantioresolution. L-tryptophan proved to be a good ligand using a common mobile phase in each case.

J. Planar Chromatogr. 31, 297-308 (2018). HPTLC of zopiclone in the presence of its degradation products, namely, 7-oxo-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazin-5-yl-4-methylpiperazine-1-carboxylate (hydrolytic DEG) and 5H-pyrrolo[3,4-b]pyrazine-5,7(6H)-dione (oxidative DEG) on silica gel with ethyl acetate – methanol – ammonia 33% 17:2:1. Quantitative determination by absorbance measurement at 303 nm. The hRF value for zopiclone was 44. Linearity was between 0.1 and 2 μg/zone. LOD and LOQ were 30 and 80 ng/zone. The intermediate precision was <2 % (n=3). Average recovery was 99.5 %.