J. Planar Chromatogr. 25, 262-268 (2012). HPTLC of paraquat (1), diquat (2), difenzoquat (3), mepiquat (4), and chloromequat (5) in water on silica gel with 1-propanol - methanol - 2.5 N NaCl 1:1:3. Quantitative determination by absorbance measurement between 500 and 535 nm. The hRf values of compounds (1) to (5) were 21, 30 36, 52 and 56, respectively. Limits of quantification were 5 ng/zone for (1), 2 ng/zone for (2), 25 ng/zone for (3), 15 ng/zone for (4) and 9 ng/zone for (5). Recovery rates for compounds (1) to (5) were 50.7, 65.2, 59.6, 45.1 and 33.7 %, respectively.

J. Planar Chromatogr. 25, 575-580 (2012). HPTLC of echioidinin-5-O-beta-D-glucopyranoside in Andrographis echioides on silica gel with chloroform - methanol 31:9. Quantitative determination by absorbance measurement at 254 nm. Linearity was in the range of 200-1400 ng/zone. Limits of detection and quantification were found to be 54 and 68 ng/zone, respectively. Recovery (by standard addition) was 96.7 %.

J. Ethnopharmacol. 138, 755-771 (2012). HPTLC studies of Harpagophytum procumbens such as the quantification of harpagoside were reviewed. HPTLC of harpagoside in the roots of Harpagophytum procumbens on silica gel with dichloromethane – methanol – acetic acid 79:20:1. Detection by dipping into anisaldehyde – methanol – acetic acid – sulphuric acid 1:170:20:10, followed by heating at 120 °C for 5 min. Quantitative determination by absorbance measurement at 285 nm. HPTLC provides comparable results with HPLC but is less time consuming.

J. Liq. Chromatogr. Relat. Technol. 35, 2396-2407 (2012). HPTLC of vanillin in the roots of Decalepis hamiltonii Wight and Arn on silica gel with toluene - ethyl acetate 9:1. Quantitative determination by absorbance measurement at 254 nm. The hRf value of vanillin was 42. Linearity was in the range of 2-12 µg/zone. Limits of detection and quantification were 1.3 and 3.9 µg/zone. The intermediate/inter-day/intra-day precision was 1.3 % (n=3), respectively. Recovery was between 99.4 and 100.3 %.

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. Planar Chromatogr. 25, 117-121 (2012). HPTLC of octachlorodipropyl ether on silica gel with toluene - acetic acid - water 20:20:1. Detection by spraying with 2 N alcoholic potassium hydroxide, followed by heating at 120 °C for 30 min, overspraying with 1 % silver nitrate in 30 % nitric acid and then exposed to unfiltered UV illumination for approximately 15 min. Quantitative determination by absorbance measurement at 399 nm. The hRf values of octachlorodipropyl ether and photodegradation products O1 and O2 were 93, 19 and 82, respectively.

Chinese J. of Med. Guide 2 (9), 109-110 (2012). Coptis chinensis is a herbal TCM drug for relieving internal heat or fever. High speed countercurrent chromatography (HSCCC) is frequently applied to analyse the alkaloids of Coptis chinensis. To optimize the solvent system of HSCCC the method for determination of the partition coefficient of Coptis chinensis alkaloids was done by TLC and fluorescence spectrophotometry. The major alkaloids are coptisine, berberine, palmatine and epiberberine. The crude drug was extracted with ethanol and contained 9.2 % coptisine, 18.5 % berberine, 4.0 % palmatine and 3.5 % epiberberine. TLC on silica gel with cyclohexane – ethyl acetate – isopropanol – methanol – water – triethylamine 6:7:2:3:1 with chamber saturation for 20 min with ammonia vapors, detection at UV 366 nm. The zones were quantitatively scraped off the layer and eluted with ethanol for fluorescence spectrophotometry at UV 366 nm. Quantification by external standard calibration over the linearity range of 0.5-2.5 g/L for coptisine, berberine and epiberberine with standard addition recovery of 98.3 % (%RSD = 1.9 %, n=6), 95.3 % (%RSD = 3.4 %, n=6), 103.9 % (%RSD = 2.6 %, n=6), respectively; and 1.0-3.0 g/L for palmatine with standard addition recovery of 97.6 % (%RSD = 3.7 %, n=6). Calculation of the partition coefficient, i.e. the ratio of observed values of the analytes from the two phases, respectively, with the results for coptisine 2.20, berberine 0.29, palmatine 0.21 and epiberberine 0.61.

J. AOAC Int. 95, 1614-1617 (2012). HPTLC of (E)-4-(3,4-dimethoxyphenyl)butadiene (DMPBD) in the rhizome of Zingiber cassumunar on silica gel with hexane - dichloromethane 3:2. Quantitative determination by absorbance measurement at 289 nm. The hRf value of DMPBD was 30. Linearity was between 130 and 703 ng/zone. LOD and LOQ were 40 and 10 ng/zone, respectively. The interday and intra-day precisions were 0.9 and 0.3 % (n=3). Average recovery (by standard addition) was 103.1 %.