The case of determination of rosmarinic acid in different matrices. J. Chromatogr. A 1220, 156-161 (2012). Description of a new method for determination of rosmarinic acid in different matrices by HPTLC on silica gel with toluene – ethyl formate – formic acid 6:4:1. Quantification by densitometry in absorbance mode at 330 nm. The influence of the main HPTLC operative parameters was figured out in view of a more stringent validation process. Together with the fundamental HPTLC instrumentation an automatic developing chamber is mandatory as it allows for control of the relative humidity and the saturation conditions and thus assures reproducibility. Several commercial preparations containing rosmarinic acid in different amounts were tested and rosmarinic acid in the range of 132-660 ng/band was found. The %RSD of repeatability and intermediate precision did not exceed 2.

J. AOAC Int. 96, 24-26 (2013). HPTLC of stevioside (1) and rebaudioside-A (2) in the leaves of Stevia rebaudiana on silica gel with ethyl acetate - ethanol - acetone - water 5:1:2:2. Detection by spraying with anisaldehyde - sulfuric acid reagent, followed by heating at 110 °C for 10-15 min. Quantitative determination by absorbance measurement at 580 nm. The hRf values of (1) and (2) were 34 and 28, respectively. Linearity was 1-7 µg/zone for both. LOD and LOQ were 127 and 387 ng/zone for (1) and 393 and 1191 ng/zone for (2). The interday and intra-day precisions were below 1.2 % (n=3). Recovery (by standard addition) ranged 89.6-93.9 % for (1) and 86.7-90.6 % for (2).

J. Anhui Med. & Pharm. 17 (2), 202-203 (2013). Banlangen granule, processed of Radix Isatidis, is a traditional Chinese herbal medicine prescribed clinically to treat sore throat, cheek swelling, acute and chronic tonsillitis and mumps. For quality control a method for the determination of leucine, a main antiviral effective component, is presented. TLC on silica gel with n-butanol – glacial acetic acid – water 19:5:5, detection by spraying with 0.1 % ninhydrin in acetone, heating at 105 °C and viewing in daylight. Quantification by densitometry at 509 nm. Validation of the method by investigation of the linearity range (0.10-0.90 µg/zone, r = 0.998, n=5), precision (%RSD = 2.8 %, n=6), stability (%RSD = 0.8 %, n=6, towards single lane within one hour), and reproducibility (%RSD = 2.0 %, n=6, within plate). The recovery (by standard addition) was 98.8 % (%RSD = 1.1 %, n=6).

Rev. Bras. Farmacogn. 23, 802-810 (2013). HPTLC of quercetin (1) and gallic acid (2) in Adiantum capillus-veneris on silica gel with toluene - ethyl acetate - formic acid 5:4:1. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 53 and 84. Linearity was in the range of 200-1600 ng/zone for both (1) and (2).

J. Planar Chromatogr. 27, 113-119 (2014). HPTLC of sulphadiazine sodium (1) and trimethoprim (2) in medicated fish feed, fish tissues, and in their veterinary pharmaceutical formulation on silica gel with chloroform - toluene - ethanol - glacial acetic acid 9:9:2:2. Quantitative determination by absorbance measurement at 270 nm. The hRF values for (1) and (2) were 48 and 16, respectively. Linearity was in the range of 100-2000 ng/zone for (1) and 100-1000 ng/zone for (2). The intermediate/interday/intra-day precisions were below 3 % (n=3). Mean recoveries for (1) and (2) were 99.6 and 97.9 %, respectively.