High-performance TLC plate

FIGURE 6.19 Circular chromatography of dyes on precoated silica gel high-performance TLC plate lipophilic dyes, mobile phase hexane-chloroform-NH3, 70 30. (From Ripphahn, J. and Halpaap, H., HPTLC High Performance Thin Layer Chromatography, Zlatkis, A. and Kaiser, R. E., Eds., Elsevier, Amsterdam, 1977, pp. 189-221. With permission.)... 

Fig. 1 Camag chromatogram immersion device set for a 10-cm dipping depth with high-performance TLC plates. Vertical dipping and removal rates and the residence time in the reagent can be preselected. [Photograph (left) supplied by D. Jaenchen, Camag, Muttenz, Switzerland schematic diagram (right) reprinted from Handbook of Thin Layer Chromatography (J. Sherma and B. Freid, eds.), p. 146, with permission of Marcel Dekker, Inc.]...

Layers often require heating after applying the reagent in order to complete the reaction upon which detection is based and ensure optimum color development. Typical conditions are 10-15 min at 105-110°C. If a laboratory oven is used, the plate should be supported on a solid metal tray to help ensure uniform heat distribution. A plate heater (Fig. 2), which contains a 20 X 20-cm flat, evenly heated surface, a grid to facilitate proper positioning of TLC and high-performance TLC plates, programmable temperature between 25°C and... 

The simultaneous analysis of multiple samples on a single plate leads to higher sample throughput (lower analysis time) and less cost per sample. Up to 36 tracks are available for samples and standards on a 10-cm x 20-cm high-performance TLC plate. 

Subsequently, thin layer chromatography (TLC) methods have been extensively evaluated to optimize the detection of laxatives/ The most important findings for the successful detection of laxatives by TLC were (1) the skill and experience of the operator, (2) the choice of the mobile phase (ethyl acetate toluene glacial acetic acid [4 16 1] and hexane toluene glacial acetic acid [3 1 1] gave the best results), and (3) use of high-performance TLC plates with a concentrating zone. 

A. Ascending Ascending chromatography is the most frequent development mode in TLC. Following sample application, a plate is placed in an appropriate chamber so that the solvent is below the point of sample application. The solvent is allowed to rise by capillary action usually from 10 to 18 cm above the origin on a 20 X 20 cm TLC plate and from 3 to 7 cm on a smaller, high-performance TLC plate. 

An adaptation of the USP TLC procedure for the determination of ordinary impurities in naphazoline hydrochloride allowed for the detection of 1-naphthylacetylethylenediamine in the presence of naphazoline. Using silica gel 60 high-performance TLC plates (20 X 20 cm) and a mobile ph of methanol-glacial acetic add-purified water (8 1 1, v/v/v), spots were visible after spraying with ninhydrin naphazoline Rf - 0.54 1-naphthylacetyl-ethylenediamine Rf - 0.63. A similar method has been described in the European Pharmacopoeia for 1-naphthylacetylethylenediamine in naphazoline nitrate S. 

Chromatographic analysis was performed on 10 X 20 cm silica gel F254 high-performance TLC plates by eluting with chloroform-methanol-formic acid (44 3.5 2.5). " ... 

This experiment (in two parts, A and B) is an introduction to the TLC separation of steroids on high-performance TLC plates. It is adapted from Whatman s TLC Technical Series, Volume 2. In A, estriol, estradiol, and estrone are separated. In B, estriol, estrone, 17-hydroxy-progesterone, pregnenolone, and progesterone are separated. 

While many practical TLC systems have been devised that utilise the principle of reversed-phase partition in the separation process, they have generally proved inconvenient and of doubtful reproducibility in use. The newer pre-coated high-performance TLC plates of this kind are much better. 

TLC plate. The majority of TLC experiments are now carried out on ready-made plates, consisting of the absorbent (silica, alumina or alkyl-bonded silica), the support and an inert binder. Conventional TLC plates are normally 20 cm X 20 cm in size, have an absorbent layer of 100-250 jxm thickness, and are coated with 20 jiim particle-size material which can be obtained in differing pore sizes (important to polymer separation). Typically 1-5 p.1 of sample are applied. More recently, high-performance TLC plates have been developed which are smaller in size (10 cm x 10 cm) and are coated with smaller particle-size absorbants (5-15 p.m) to increase separating power. When such plates are used, sample loadings can be as little as 0.1-0.2 il. 

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