Developing chambers automated multiple development

Automated multiple development (chamber) (2) Atmospheric mass detector (3) Advanced method development... 

Figure 6.11. Schematic diagram of the automated multiple development chamber. Identification 1 = developing chamber 2 = solvent reservoirs 3 = solvent selection valve 4 = solvent mixer 5 = wash bottle for preparation of the gas phase for layer conditioning 6 = gas phase reservoir 7 = vacuum pump and 8 = solvent waste reservoir.

To estimate the content of dihydro-2,5-dihydroxy-6-methyl-4//-pyran-4-one (DDMP) saponin and saponin B in selected pea cultivars, an HPTLC method was developed [35]. Silica gel 60 F254 plates were prewashed with methanol and activated at 100°C prior to development in automated multiple development chamber AMD2 using chloroform-methanol-water (55 37 8, v/v). Densitometry, after postchromato-graphic derivatization with anisaldehyde-sulfuric acid, revealed the prevalence of saponin B over DDMP saponin in all pea cultivars. The identities of the two com-ponnds were determined by coupling HPTLC directly to ESI-MS and additionally by offline MALDI-TOF/TOF-MS by application of a purified extract/matrix mixture onto a standard steel MALDI plate. HPTLC plates intended for MS analysis were developed with a modified developing solvent chloroform-methanol-water (6.5 3.5 0.9, v/v). The analytes were eluted from the plates with 0.1% formic acid-acetonitrile (40 60, v/v) by means of TLC-MS interface (CAMAG) and transferred into the ESI-MS system, which operated in positive-ion mode. 

Figure 23 HPTLC-FTIR transmission spectra (A) and chromatogram (B) of cobaIt(III)-EDTA (edetic acid) complex AMD (automated multiple development) chamber (CAMAG) with ammontacal methanol-dichloromethane solvent gradient.

Fig. 2 The steps in the process of thin-layer chromatography that have been instrumentalized and automated to a large degree in the recent past. PMD = Programmed Multiple Development, AMD = Automated Multiple Development, DC-Mat or ADC = Automatic Development Chamber.

A technique that can achieve the maximum attainable resolution in TLC on a given separation distance without forced flow is automated multiple development (AMD). This step-gradient technique was developed by Burger. With respect to peak capacity the technique can be compared to HPLC, but it still maintains all benefits of planar chromatography. The heart of the instrument is a specially designed vacuum-tight chamber. Following sample application... 

Important new instruments were developed after the UM chamber, aimed at increasing the efficiency of TLC through improvement of the separation mechanism. Programmed multiple-development TLC as elaborated by Perry (12) combines the techniques of continuous multiple development and evaporation. Recently this technique was improved by Burger (13). In this system the chomato-plate is developed several times in the same direction with various eluents of decreasing elution power. Between developments the chromatoplate is dried by vacuum. This method is termed automated multiple development (AMD) (14). High-performance TLC (HPTLC) is based on the use of chromatoplates coated with fine particles of narrow particle size distribution sorbent and is carried out with sophisticated instrumentation (15,16). 

Steroids have been extensively investigated using instrumental techniques such as overpressured layer chromatography (2,4,17,34,55), parallel development TLC (56), programmed multiple development [57], and automated multiple development/AMD (58). Each technique has been reported to furnish a significant improvement in separation selectivity in comparison with development in conventional TLC chamber systems. 

Chloitetracycline, 468-472 Cholecalciferol (vitamin Da), 1061 Chromatogram development, 135-140 automated multiple development, 138-140 automatic chromatogram development, 138 general aspects of development, 135-137 horizontal developing chamber, 138 in a tank, 137-138 Chromatorods, 362 Chromatostrips, 362... 

This method utili2BS a fiilly automated developmg chamber that consists of a sensor to optically detect the solvent fiont position, a mechanism to lift the plate out of the developing chamber, multiple solvent reservoirs, a solvent pump, and an integrated fen to dry the plate and remove solvent vapor. Modem systems contain microprocessor-controlled programming to vary solvent composition after each run. Multiple development dramatically increases separation power, improves reproducibility and precision, and can be set up to run without continuous supervisioa This apparatus can also be used in conjunction wife a TLC plate scanner feat will detect UV-active bands. This can be interfaced wife a PC and linked to a printer for hard copy. An excellent example of an AMD device is fee CAMAG AMD system (Merck). 

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