CBS 93, 10-12 (2004). HPTLC of progesterone on silica gel prewashed by development in AMD2 first with chloroform - methanol 1:1 and then with the mobile phase, followed by drying at 80 °C for 15 min. Development in AMD2 with toluene - 2-propanol 10:1 without preconditioning over 60 mm. Quantitative determination by absorbance measurement at 252 nm followed by spectra recording from 200 to 360 nm. The linear working range is 25.7-154.5 ng/zone. Repeatability (standard deviation calculated from the amounts of seven simulated progesterone samples determined on the same plate at three concentration levels in the lower, middle and upper range) is 0.26-1.29 %. Recovery is 99.88-100.97 %. Reproducibility was performed with recycled HPTLC plates.

Indian Drugs 41 (6), 354-357 (2004). HPTLC on silica gel with toluene - methanol - acetone - 10 % ammonia 80:40:20:1. Quantitative determination by absorbance measurement at 254 nm. The Rf value of pioglitazone hydrochloride was found to lie between 0.49-0.55. The linear dynamic response was found to be 2.0-4.0 µg/spot for pioglitazone hydrochloride. The results of the analysis have been validated statistically and by recovery studies. A simple, fast, specific and precise HPTLC method has been developed for the estimation of pioglitazone hydrochloride in its tablet dosage form.

CBS 94, 14-15 (2005). HPTLC of sucralose on amino phases with acetonitrile - water 4:1 over 70 mm. Stability of sucralose in Burfi, a milk-based confection, was determined over a defined time period. The 2 products of hydrolysis have been monitored as well. Detection by heating for 20 min at 190° C. Quantitative determination by fluorescence measurement under UV 366. Limit of quantitation in the lower ng range.

J. Planar Chromatogr. 17, 355-359 (2004). HPTLC of aristolochic acid A, B, and C and numerous plant extracts on silica gel in a saturated twin-trough chamber using the upper phase of the mixture toluene - ethyl acetate - water - formic acid 20:10:1:1. Quantitative determination by fluorescence measurement at 366 nm after derivatization with tin(II) chloride reagent. The working range and linearity, LOD and LOQ (based on the calibration plot), and precision (n = 6), were validated with methods described by K. Ferenczi-Fodor et al., J. AOAC Int. 84 (2001) 1265-1276. The stability of the analyte during chromatography was established by two dimensional chromatography. The new method enables visual detection of the acids with certainty at very low levels (400 pg absolute of aristolochic acid A) in plant material and can therefore be used for screening Chinese drugs to ensure their safety on the basis of absence of aristolochic acid.

Part I. J. Planar Chromatogr. 17, 275-279 (2004). HPTLC of nicotinic acid and selected derivatives (methyl nicotinate, ethyl nicotinate, isopropyl nicotinate, butyl nicotinate, hexyl nicotinate, benzyl nicotinate, nicotinamide, N-methyl nicotinamide) on RP-18 with methanol - water in different volume proportions after chamber saturation for 30 min. Detection under UV light at 254 nm. Investigation of the lipophilicity by TLC and use of the data for quantitative structure-activity relationships.

Chromatographia 58 (11-12), 781-788 (2003). Ten urea herbicides and fungicides have been separated by use of two-dimensional thin-layer chromatography. The largest differences are obtained by combination of normal-phase (NP) system and reversed-phase (RP) system on cyanopropyl-bonded polar adsorbents and on two-adsorbent layer containing a narrow zone of octadecyl silica and adjacent a wide zone of silica (or vice versa). The greatest spread of points was obtained for combination of nonaqueous NP systems with ethyl acetate on silica and RP systems comprising a polar solvent (methanol) in water on octadecyl silica adsorbent wettable with water (RP-18W). A good spread of points was also obtained for pairs of normal-phase systems with heptane-ethyl acetate mobile phases and reversed-phase systems with water-dioxane mobile phases, both on cyanopropyl-bonded polar adsorbents. The correlations of Rf values in NP/RP systems were utilized in practical separation of a mixture of ten urea pesticides using 2D-TLC on these adsorbents. The plates were scanned and videoscanned showing the real pictures of TLC chromatograms.

J. Planar Chromatogr. 18, 221-223 (2005). HPTLC of horminone on silica gel in a twin-trough chamber with hexane - dioxane 9:1. Absorbance measurement at 271 nm. For fluorescence analysis the plates were dipped in 1 % diphenylboryloxyethylamine in ethyl acetete for 2 s, followed by drying and dipping in a solution of 5 % PEG 8000 in dichloromethane for 2 s. After 15 min fluorescent zones of horminone were scanned at 366/>400 nm. Use of the fluorescence reagent successfully reduced the limits of detection and quantification to 0.75 ng/spot and 1.51 ng/spot, respectively. Linearity range was from 60-300 ng/spot.

J. Planar Chromatogr. 18, 39-43 (2005). Micropreparative TLC of 10 pesticides (isoproturon, diuron, momolinuron, desmetryn, methiocarb, atrazine, fenitrothion, terbutryn, bromopropylate, aziprotryne) for preliminary fractionation on silica gel in horizontal DS chambers with tetrahydrofuran - n-heptane 1:4; detection under UV at 254 nm. HPTLC of the separated fractions on RP-18 W with methanol - water 3:2 and acetonitrile - water 3:2; densitometry at 254 nm.