IPC 56th 2004, Abstract No. CP-32. A stability indicating HPTLC method has been developed for the analysis of solid dosage forms containing beta-carotene. HPTLC of beta-carotene on silica gel with petrol ether (40-60 °C) - methanol - toluene 4:8:1. Rf value of beta-carotene was 0.65-0.70. Quantification by densitometric evaluation at 460 nm. The method was validated for accuracy, precision, linearity, and stability, and can be adopted for routine analysis of beta-carotene in formulations.

J. Planar Chromatogr. 18, 73-77 (2005). HPTLC of isoflavonoids (puerarin, 3’-methoxypuerarin, daidzin, and daidzein) from Kudzu samples (a perennial leguminous plant of the genus Pueraria) on silica gel with chloroform - methanol - ethyl acetate- water 81:94:260:15. Quantitative determination by absorbance measurement at 254 nm. Repeatability and accuracy of HPLC compared with HPTLC are better, but separation of isoflavonoids by HPLC is time consuming and difficult. HPTLC is simple and rapid without tedious isolation of isoflavonoids. Separation and quantification of isoflavonoids from stem and leaf samples of kudzu is only achieved by HPTLC.

J. AOAC Int. 88, 1555-1561 (2005). HPTLC of chloramphenicol on silica gel in a horizontal developing chamber (36 applications per plate) using n-hexane -ethyl acetate 7:13. Quantitative determination by absorbance measurement at 280 nm. Mean recovery was 95.8 %, and the coefficient of variation was 5.8 %. The detection limit was 3 ng, and the quantitation limit 10 ng.

J. Planar Chromatogr. 18, 377-379 (2005). HPTLC of 2-azaanthraquinone from plant extracts on silica gel with toluene - ethyl acetate - methanol 40:9:1. Quantitative determination by absorbance measurement at 310 nm. Calibration was linear in the range of 10-100 µg/mL. The method was repeatable and precise with RSD between 0.98 and 1.59 % intra-day and between 3.41 and 5.56 % inter-day. Limits of detection and quantification were 3 and 6 µg/mL.

Hosp. Pharm. (Zhongguo Yiyuan Yaoxue Zazhi) 25 (9), 894-896 (2005). TLC of the extracts on silica gel plates with acetone - ethanol - hydrochloric acid 10:6:1. Detection by spraying with potassium iodobismuthate solution. Identification by comparison with the standard. Quantification by densitometry at 510 nm. Validation of the method by investigation of linearity range (2.2 µg - 10.8 µg, r = 0.9994); precision (RSD = 1.05 %, n = 5); reproducibility of five time assay towards the same sample (RSD = 0.31 %); and standard addition recovery (98.1 %, RSD = 2.15 %, n = 5). The results for five real life samples are given.

J. Planar Chromatogr. 18, 34 -38 (2005). Considering the latest technical and methodological developments, modern high-performance thin-layer chromatography, also known as planar chromatography, is a reliable and powerful analytical technique, in full compliance with current good-manufacturing practice (cGMP). With the proper equipment TLC is the method of choice when many samples must be analysed at low cost per sample. Advantages of HPTLC are shown in the analysis of botanicals: 1) Identification (separation of Stephania tetrandra root extracts with tetrandrine as standard on silica gel with toluene - ethyl acetate - methanol -ammonia 100:100:50:3; detection under UV at 254 and 366 nm, under white light after derivatization with iodine, and under UV at 366 nm after derivatization with anisaldehyde. 2) Semi-quantitative assessments in process control and stability tests (separation of fatty acids of Saw Palmetto products on RP-18 by two fold development with dichloromethane - acetic acid - acetone 2:4:5. 3) Quantitfication of marker compounds, like curcumin measured at 366 nm/>400 nm on silica gel with toluene - acetic acid 4:1. 4) Choice of stationary phase (separation of flavonoids on conventional TLC plates and on HPTLC plates with formic acid - water - ethyl methyl ketone - ethyl acetate 10:10:30:50 and detection with natural products reagent; switching to HPTLC reduced analysis time to a quarter and gave sharper bands). 5) Choice of mobile phase; 6) Derivatization and 7) Chromatogram evaluation.

J. Planar Chromatogr. 18, 160-163 (2005). TLC of rare earths (La(III), Ce(III), Pr(III), Sm(III), Gd(III), Er(III)) on silica gel and silica gel impregnated with 2.5 M ammonium nitrate with different mixed mobile phases containing di(2-ethylhexyl)dithiophosphoric acid as a complexing agent. The best results were obtained by use of ethyl methyl ketone - tetrahydrofuran - 1 M di(2-ethylhexyl)dithiophosphoric acid 17:8:1. Double development was used to obtain better separation of consecutive rare earths.

J. AOAC Int. 89, 1-7 (2006). TLC of masticadienonic and 3-hydroxymasticadienonic acid on silica gel with hexane - acetone - formic acid - acetic acid 30:10:1:1. Quantitation by determination of the absorption at 200 nm. Detection by dipping into anisaldehyde - sulfuric acid reagent for 1 sec and heating at 100 °C for 5 min. Limit of detection was 0.1-0.2 µg/mL.