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Five dyes as new visualizing reagents, namely gentian violet, methylene violet, methylene blue, malachite green, and Janus blue, have been used to detect estradiol on neutral aluminum oxide 60F 254 and on neutral aluminum oxide 150F 254 . Barton's reagent, rhodamine B, and sulphuric acid were used as the comparative visualizing reagents. Limit of detection (detectability), detection index, modified broadening index, modified contrast index, and linearity range were determined for estradiol following use of these visualizing reagents. It was stated, that the proposed modified contrast index is the objective parameter describing the applied visualizing reagents. The influence of a solid support on obtained visualizing effects was found. The angles (a) between the tangents at the inflection points to the curves of the densitometric peaks are more compact on neutral aluminum oxide 60F 254 than on neutral aluminum oxide 150F 254 . This observation indicates that the utility of any particular visualizing reagent depends on the type of chromatographic support used. For the quantitative research of estradiol investigated, relatively good properties had sulphuric acid (VI), Barton's reagent, gentian violet, and methylene violet.

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Vitamin K 1 (phylloquinone) was investigated with the use of reversed phase thin layer chromatography (RP-TLC) on RP8F 254s , and RP18F 254s (E. Merck) plates, using methanol as a mobile phase. It was stated that a larger amount of the bands on a chromatogram were obtained on RP8F 254s plates than on RP18F 254s plates. Six densitometric bands on RP8F 254s plates were observed, where vitamin K 1 had R F ¼ 0.45 and k max ¼ 254 nm; however, the impurities had the R F values equal to 0.27, 0.54, 0.59, 0.62, and 0.75, respectively. It was stated that RP-TLC with densitometry and spectrodensitometry is a good method for the analysis of the qualitative composition of vitamin K 1 .