J. Chromatogr. A 1217 (43), 6600-6609 (2010). A review on hyphenations of planar chromatography and its most important subcategory HPTLC. Examples from the field of natural product search, food, and lipid analysis point out the hyphenation with effect-directed analysis and mass spectrometry and illustrate the efficiency gain. Depending on the task at hand, hyphenations can readily be selected, for example with MS, bioassays etc. as required to reach the relevant information about the sample. At the same time, information is obtained for many samples in parallel. The flexibility and the unrivalled features through the planar format valuably assist separation scientists.

CBS 118, 1-4 (2017). Screening of steroids and selective androgen receptor modulators (SARMs) in bodybuilding supplements by HPTLC of methanedienone, ibutamoren, and ostarine on silica gel with n-heptane – ethyl acetate 1:1 (steroids) and dichloromethane – methanol 9:1 (SARMs) to the migration distance of 70 mm. Detection by immersion into (1) toluene sulfonic acid reagent (10 % in ethanol) followed by heating at 150 °C for 3 min, or (2) Seebach reagent (5 g phosphomolybdic acid, 2 g cerium sulfate and 12 mL sulfuric acid made up to a volume of 200 mL with water) followed by heating at 110 °C for 5 min. Detection under UV 254 nm, 366 nm and under white light. Densitometric evaluation by multi-wavelength scan at the respective absorption maxima. For example for the steroid testosterone the LOD was 8 ng/zone (absorbance measurement at 250 nm). Direct elution of target zones into the MS and analysis in positive ionization mode.

J. Planar Chromatogr. 2, 77-79 (1989). HPTLC of urine extracts on silica with ethyl acetate - methanol - NH3 25% 85:10:5. Doping control by post-chromatographic derivatization. Esidrex and similar drugs as well as their metabolites are converted into azo dyes. Drug monitoring by densitometry. Determination limit of the method described is 0.2 mg/L and the sensitivity limit is 0.1 mg/L. The procedure allows the analysis of a large number of samples in a short period of time with minimal operating costs.

J. Planar Chromatogr. 6, 415-418 (1993). TLC of 4 drug mixtures (hydroxyethyltheophylline/sulfadimidine, hydroflumethiazide/theophylline, carprofen/flunixin, frusemide/caffeine) and 11 corticosteroids on silica with 5 different mobile phases (ethyl acetate - methanol 0.880 NH3 80:25:10; dichloromethane - dioxan - water 100:50:50; lower layer; chloroform - methanol 95:5; toluene - ether - acetic acid - water 120:60:18:1. Detection and/or quantification by densitometry (no details).

J. Planar Chromatogr. 8, 388 - 392 (1995). HPTLC of MDA.HCl, MDMA.HCl, MDE.HCl, BDB.HCl, MBDB.HCl, LSD, and atropine on silica with dichloromethane - methanol 200:3 in the presence of NH3 in a separate 10 mL glass vessel for LSD, ethyl acetate - acetone - methanol - 25% NH3 50:50:20:1 for MBDB, acetone - ethanol - 25% NH3 90:7:3 for atropine. Identification by in situ FTIR measurement.

J. Chinese Trad. and Herb. Drugs (Zhongcaoyao), 36 (2), 222-224 (2005). TLC on silica gel with chloroform - methanol - water 70:35:4. Detection by spraying with 10 % H2SO4 in ethanol and heating at 105 °C for 5 min. Identification by fingerprint technique. Quantification by densitometry at 530 nm. Validation of the method by investigation of linearity (0.458 µg - 2.748 µg, r = 0.998); precision (RSD = 2.48 %, n = 5 within plate and RSD = 4.69 % plate to plate); reproducibility of five time assay towards the same sample (RSD = 2.41 %); and standard addition recovery (96.11 %, RSD = 1.91 %, n = 5). The results for real life samples are given.

Chromatographia 67 (5-6), 441-447 (2008). HPTLC of forskolinon on silica gel aluminium foil with benzene - methanol 9:1. Quantitative determination by densitometry in the absorbance mode at 545 nm after spraying with anisaldehyde sulphuric acid reagent. The method was validated: linearity was between 100 and 1000 ng/spot (r = 0.994) and the limits of detection and quantification were 8 and 27 ng/spot respectively. Application of the proposed method for determination of forskolin in Coleus forskohlii root and in capsule dosage forms, which showed 0.18 and 0.57 % w/w of forskolin, which was subjected to acid and alkali hydrolysis, oxidation, photodegradation and heat degradation. The method shows good repeatability, selectivity and accuracy, and effectively separates forskolin from components of C. forskohlii root, from excipients of capsule as well as the degradation products of forskolin. It can be used for routine analysis and as a stability-indicating method.

Chinese J. Hosp. Pharm. (Zhongguo Yiyuan yaoxue Zazhi) 25 (1), 90-92 (2005). TLC on silica gel with chloroform - ethyl acetate - formic acid 2:2:1. Detection under UV light. Identification by fingerprint technique. Quantification by densitometry at 325 nm. Validation of the method by investigation of linearity (0.52 µg - 4.68 µg, r = 0.9992); precision (RSD = 2.20 %, n = 5); reproducibility of five time assay towards the same sample (RSD = 3.10 %); standard addition recovery (99.0 %, RSD = 0.26 %, n = 5). The results for three real life samples are given.