Part III. Application of terms describing the separation of homologous series of saturated fatty acids in TLC. J. Planar Chromatogr. 16, 303-307 (2003). HPTLC of 19 fatty acids (from pentanoic to tricosanoic acid) on RP-18, with and without concentrating zones. The best chromatographic conditions for separation were on RP-18 without concentrating zone with methanol - water 9:1, 19:1 and ethanol - water 9:1, and on RP-18 with concentrating zone with methanol - water 9:1 and 19:1, 100% ethanol and ethanol - water 9:1 and 19:1. Visualization by exposure to iodine vapor. Optimization of separation conditions.

(Laminaceae) leaves. J. Planar Chromatogr. 17, 18-21 (2004). TLC of polyphenols and rosmarinic acid on silica gel with 1) toluene - methyl acetate - formic acid 5:4:1; 2) ethyl acetate - methanol - water 77:13:10; 3) ethyl acetate - diethyl ether 8:2. Detection a) at 254 nm, b) in fluorescence after spraying with Neu-PEG reagent, and c) in visible light after spraying with 10 % iron(III) chloride solution. Quantitative determination by densitometry at 254 nm and spectra recording from 200 to 500 nm for identification.

J. Chromatogr. A 1216 (25), 5057-5060 (2009). Paper chromatography of gamma-aminobutyric acid. The method consists of application, separation and detection and is clean, rapid, inexpensive and reproducible compared to the routine paper chromatography. The derivatization procedure with ninhydrin reagent was optimized regarding reagent concentration, derivatization temperature and time and Cu2+ concentration. Quantification of gamma-aminobutyric acid by combination of with Vis spectrophotometry. The limit of detection was 0.05 mg/mL and the linear range was from 0.5 to 20.0 mg/mL. The determination coefficient was r2 = 0.998. The method was accurate (%RSD < 2.6 %), and recoveries were 102.7-103.9 %.

Asian Journal of Chemistry 23(2), 977-979 (2011). Part of the aqueous extract of Orthosiphon stamineus (Lamiaceae) was chromatographed on a silica gel column and eluted with n-hexane - ethyl acetate 3:2. The eluate was concentrated in order to obtain betulinic acid for use as standard solution. TLC on silica gel with n-hexane - ethyl acetate - formic acid 150:100:1. For derivatization the plate was sprayed with anisaldehyde reagent followed by heating at 100 °C for 10 min. Quantification of betulinic acid by densitometric measurement in fluorescence mode at 366 nm. The method was linear in the range of 0.2-500 µg/band. The recovery was 96.1-98.4 %.

Analytical Chemistry - An Indian Journal 9(1) (2009). An HPTLC method has been developed for simultaneous estimation of paracetamol and ibuprofen. HPTLC on silica gel with ethyl acetate - acetone - n-butanol - 25 % ammonia 3:4:3:1. Densitometric quantification at 254 nm. The hRf value of ibuprofen was 32 and of paracetamol 86. The method was linear in the range of 120-600 ng/band for paracetamol and 130-650 ng/band for ibuprofen.

62nd Indian Pharmaceutical Congress Abstract No. F-252 (2010). TLC of alizarin and betulinic acid on silica gel with toluene – ethyl acetate – formic acid 18:3:1. The hRf values were 53 and 58 for betulinic acid and alizarin, respectively. Quantitative determination by absorbance measurement at 287 nm. The method was linear in the range of 60-160 ng/band for alizarin and 300-800 ng/band for betulinic acid. The average recovery was in the range of 99.4-99.6 % for both compounds.

International Journal of PharmTech Research 3(2), 986-999 (2011). TLC of methanolic extracts of Haritaki and gallic acid and rutin as markers on silica gel with toluene - ethyl acetate - formic acid 3:6:1 for gallic acid and chloroform - ethyl acetate - methanol - formic acid 7:10:1:2 for rutin. Quantitative determination by densitometry in absorbance mode at 280 nm for gallic acid and 254 nm for rutin. The method was linear in the range of 100-500 ng/band for gallic acid and 1000-5000 ng/band for rutin. The recovery was 99.1 % for gallic acid and 97.9 % for rutin. The LOD and LOQ of gallic acid was 71 and 213 ng/zone and of rutin 63 and 189 ng/zone.

J. Planar Chromatogr. 26, 336-342 (2013). HPTLC of diosmin (1), hesperidin (2), and ascorbic acid (3) on silica gel with ethyl acetate - methanol - water 15:3:2 for (1) and (2) and ethyl acetate - methanol - water - acetic acid 15:10:2:1 for (3). Quantification by absorbance measurement at 340 nm for (1), 286 nm for (2) and 265 nm for (3). The hRf values for (1), (2) and (3) were 34, 40 and 56, respectively. Linearity was in the range of 100-800 ng/zone for (1) and (2) and 50-400 ng/zone for (3). LOD and LOQ were 6 and 17 ng/zone for (1), 4 and 13 ng/zone for (2) and 4 and 13 ng/zone for (3), respectively. Recoveries were in the range of 98.1-99.3 % for (1), 98.4-99.5 % for (2) and 98.0-99.1 % for (3). Intermediate/interday/intra-day precision was below 2 % (n=6).