Automated Developing Chamber

Szabady, B. Fater, Z. Nyiredy, S. Comparative study of automated development chambers. J. Planar Chromatogr.-Mod. TLC 1999,12, 82-88. 

Coupled spectroscopic methods such as TLC-UV (ultraviolet) and visible spectroscopy, TLC-mass spectrometry, and TLC-FTIR (Fourier transform infrared) have been developed to overcome this difficulty [7]. Their future application in the TLC analysis of natural pigments will markedly increase the information content of this simple and interesting separation technique. The automation of the various steps of TLC analysis (sample application, automated developing chambers, TLC scanners, etc.) greatly increased the reliability of the method, making it suitable for official control and legislative purposes [8]. 

Interesting advances have been made in TLC such as an automated development chamber which improves reproducibility, a cutting technology which can be used with pre-coated plates, a densitometer for quantitative evaluation of plates, as well as new computerised application databases [36]. TLC plates are getting smaller in size (surface) which leads to an increase in elution speed and to a decrease in solvent consumption. 

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.

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

Beesley21 has described some special development chambers designed for nonconventional TLC operation. Camag has produced an automated radial system whose operation closely approximates that used in column LC. A syringe pumps mobile phase into the center of a plate, and a sample is injected into the flowing stream and is separated as concentric circles on the plate. 

Another device for automated development is the chamber constructed by Tyihak [4], in which the adsorbent layer is placed between two plates and the mobile phase flows under increased applied pressure. It can be operated in the linear or radial mode. Another automated device is the UMRC (Ultra Micro Rotation Chromatograph), where the eluent is delivered to the center of a rotating TLC plate [5]. A simple device was constructed by Delvorde and Postaire [6] in which the liquid is pumped out (by vacuum) which causes the flow of the mobile phase and decreases the vapor pressure. 

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). 

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.

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... 

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