J. Chinese Modern Med. & Pharm. 18 (1), 40-42 (2011). TLC on silica gel with petroleum ether (60-90 ºC) – ethyl acetate 1:1. Detection under UV 254 nm. Identification by comparison of the fingerprint of the main component, Rehmanniae Radix.

J. Chromatogr. A 1218 (19), 2785-2792 (2011). Examination of the applicability of TLC for the analysis of biodiesel conversion. Biodiesel is a complex mixture which complicates the analytical separation and requires a large set of data for understanding reaction kinetics. A flame ionization detector (FID) and a modified TLC staining procedure were evaluated in comparison with the well-established but time-consuming and expensive GC and HPLC methods. The TLC staining method is suited for quantitative analysis due to no background. Demonstration by using several experimental samples produced by enzymatic conversion of rapeseed oil to biodiesel. It was found that the first reaction step (6 h) resulted in 85–95 % conversion and the second step (after removal of glycerol and water) increased the yield to 97–98 %. All components of the mixtures were separated and quantified. Relation of the biodiesel contents measured by TLC and GC gave the values of 1.03 ± 0.07 (TLC-staining) and 0.95 ± 0.04 (TLC–FID), which indicated the applicability of the TLC methods.

J. Planar Chromatogr. 24, 423-427 (2011). HPTLC of salmeterol xinafoate (as salmeterol base SAL and xinafoic acid XIN) on silica gel with ethyl acetate - methanol - 33 % ammonia 16:3:1 with chamber saturation for 1 h. Detection under UV light at 254 nm. Quantitative determination by densitometry at 300 nm (SAL) and at 250 nm (XIN). The hRf value was 48 for SAL and 36 for XIN. Linearity was betwen 1-6 µg/zone for SAL and 0.5-4 µg/zone for XIN. The recovery (by standard addition) was 100.6 % for SAL and 99.8 % for XIN. The intra-day and inter-day precision, as %RSD, was 0.7 and 1.1 % for SAL, and 0.9 and 1.0 % for XIN. The limit of detection and of quantification was 0.4 and 1.2 µg/zone for SAL and 0.1 and 0.3 µg/zone for XIN.

International Journal of ChemTech Research 1(3), 677-689 (2009). HPTLC of rosuvastatin in raw material and tablet dosage formulation on silica gel with ethyl acetate - toluene - acetonitrile - formic acid 60:35:5:2. The hRf value was 85. Quantitative evaluation by absorbance measurement at 243 nm. The method was found to be linear in the range of 318-3816 ng/band. The mean recovery was 99.7 %. The sample was subjected to different stress conditions and the degradation products were well separated from the main drug.

J. Liq. Chromatogr. Relat. Technol. 32, 1273-1288 (2009). HPTLC of Sudan I (1), II (2), III (3), IV (4), Sudan Red B (5), Sudan Red 7B (6), Sudan Red G (7), Para Red (8), FD&C Orange 2 (9), Butter Yellow (10), Citrus Red 2 (11), Toluidine Red (12), and Disperse Orange 11 (13) in paprika, chili, and curry on RP-18 with acetonitrile - ammonia 25 % 19:1. Quantitative determination by absorbance measurement at absorption maxima of each dye. The hRf values of compounds (1) - (13) were 61, 54, 48, 29, 18, 11, 69, 63, 56, 48, 39, 18 and 11, respectively. Visual detection limits were 3 ppm for most dyes in either matrix, 5 ppm for Sudan I, 13 ppm for Disperse Orange, and 7 ppm for Butter Yellow. The limits of detection by densitometry were lower by a factor of 2 for all dyes and values of 1-3 ppm were reached except for Disperse Orange with a limit of detction of 7 ppm. Average recoveries ranged from 95.0-110.8 %. The HPTLC method is successfully applied in the routine control of illegal dyes in food by surveillance authorities.

J. Planar Chromatogr. 24, 331-336 (2011). HPTLC of pioglitazone (PIO), metformin (MET), and glimepiride (GLI) in pharmaceutical preparations on silica gel, prewashed with methanol, with acetonitrile - methanol - propanol - ammonium acetate solution 7:2:1:1 in a twin trough chamber saturated for 10 min. Quantitative determination by densitometry at 240 nm. The hRf value was 83, 21, and 89 for PIO, MET, and GLI, respectively. Linearity was in the concentration range of 300-1200 ng/band, 10-40 µg/band and 40-160 ng/band with correlation coefficients of 0.995, 0.996, and 0.998 for PIO, MET, and GLI, respectively. The LOD and LOQ was 57 and 171 ng for PIO, 6 µg and 18 µg for MET, and 12 and 36 ng for GLI. The %RSD for method and intermediate precision was below 2 %. The mean recovery (n = 5) was 98.2-99.5 % for PIO, 98.6-99.3 % for MET, and 98.7-99.7 % for GLI with %RSD between 0.4 and 1.3 %.

Planta Med. 74, 352-353 (2008). HPTLC of tetraphyllin, turneradiffusin, beta-arbutin, terniflorin, echinaticin, turneradin and methanolic extracts of Turnera diffusa on silica gel with ethyl acetate - acetic acid - water 190:10:1. Quantitative determination by densitometric absorbance measurement at 254 nm.

CBS 107, 2-4 (2011). To ensure effective cleaning of the reaction vessels in pharmaceutical production wool swabs are used to swipe a defined area of the vessel. The wool swabs are extracted with chloroform and the extracts are applied as rectangles of 4x3 mm. HPTLC on silica gel with toluene - ethyl acetate 3:2 with chamber saturation for 10 minutes. Identification of substances by densitometric spectra recording between 200-350 nm followed by 3-level calibration. Detection by spraying or immersion in methanol - sulfuric acid 9:1 and heating for 5 min at 105 °C. Evaluation under visible light and UV 366 nm.