Horizontal chambers

Some beehive ovens, having various improvements and additions of waste heat boilers, thereby allowing heat recovery from the combustion products, may stiU be in operation. Generally, however, the beehive oven has been replaced by waH-heated, horizontal chamber, ie, slot, ovens in which higher temperatures can be achieved as well as a better control over the quality of the coke. Modem slot-type coke ovens are approximately 15 m long, approximately 6 m high, and the width is chosen to suit the carbonization behavior of the coal to be processed. For example, the most common widths are ca 0.5 m, but some ovens may be as narrow as 0.3 m, or as wide as 0.6 m. 

Heterocyclics 252, 260, 299,416 n-Hexadecanol esters 63 Hexaporphyrin 102 Hexitols 426 Hexobarbital 254,255 Hexoses 161,202 Hexuronic acid 158 Histamine 294,296, 355 Homogentisic acid 166,167 Horizontal chamber 127 Hotplates 93 ff -, temperature distribution 95 Hydrazines 269,284 Hydrazone formation 71 ff -with 2,4-dinitrophenylhydrazine 71, 72, 274... 

Chapter 4 discusses the selection and optimization of mobile phases for successful separations in PLC. Chapter 5 details procedures for sample application and development of layers, and Chapter 6 complements Chapter 5 by dealing specifically with the use of horizontal chambers for the development of preparative layers, including linear, continuous, two-dimensional, gradient, circular, and anticircular modes. 

FIGURE 6.9 Horizontal chamber for fully online HPTLC by Nyiredy 1 — evaporator, 2 — diode-array detector, 3 — quartz glass cover plate, 4 — septum, 5 — injector block, 6 — mobile phase, 7 — filter paper, 8 — Teflon chamber, 9 — chromatoplate. (Modified from Nyiredy, Sz., J. Planar Chromatogr. 15, 454-457, 2002.)... 

FIGURE 6.10 The cover of the prepared chromatoplate for gradient development in a fully online horizontal chamber 1 — solvent system inlet, 2 — Silcoflon cover sheet, 3 — chromatoplate, 4 — solvent system outlet, 5 — channel for solvent system. (From Nyiredy, Sz. and Benko, A., Proceedings of the International Symposium on Planar Separations, Planar Chromatography 2004, Nyiredy, Sz., Ed., Research Institute for Medicinal Plants, Budakalasz, 2004, pp. 55-60. With permission.)... 

Isocratic linear development is the most popular mode of chromatogram development in analytical and preparative planar chromatography. It can be easily performed in horizontal chambers of all types. The mobile phase in the reservoir is brought into contact with the adsorbent layer, and then the movement of the eluent front takes place. Chromatogram development is stopped when the mobile phase front reaches the desired position. Usually 20 X 20 cm and 10 X 20 cm plates are applied for preparative separations, and this makes the migration distance equal to about 18 cm. Due to the fact that the migration distance varies with time according to the equation Z, = (Z, c, and t are the distance of the solvent front traveled, constant,... 

As mentioned earlier, the preceding chromatogram development on the full length of the 20-cm plate takes a lot of time. To overcome this problem, the development of chromatogram on a short distance with simultaneous evaporation of the mobile phase from the exposed part of the chromatographic plate can be very conveniently performed by means of horizontal chambers. The mode was introduced by Perry [23] and further popularized by Soczewinski et al. [24,26], using a horizontal equilibrium sandwich chamber. 

The device for continuous gradient elution in horizontal chamber described by Nyiredy [15] and presented in the preceding text, (Figure 6.10) seems to be a very interesting solution both for analytical and preparative applications. 

Most horizontal chambers enable convenient and economical regeneration of the layers. The procedure is as follows (1) press the blotting or chromatographic... 

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