Tubular TLC

A variation of this technique involves the use of quartz tubes coated on the inner surface with silica gel or silica gel -f CuO instead of adsorbent-coated glass rods. In the tubular TLC (TTLC) method, fractionation on the chromatotubes is carried out as in conventional TLC, followed by drying of solvent by... 

The technique of TLC using chromatotubes, also termed tubular TLC (2,3,7), was later modified by using different principles of vaporization of the fractions, e.g. combustion in situ on an adsorbent containing cupric oxide and detection of the carbon dioxide formed in a TCD with the aid of helium as carrier gas (8,9). The techniques of pyrolysis/evaporation on an adsorbent, such as silica gel, and combustion on an adsorbent containing cupric oxide have been subsequently integrated into a single instrumental system using the more sensitive vapor phase detector, i.e. FID, as will be described later. 

The following discussion is devoted to a description of the techniques of tubular TLC and coated rod TLC in conjunction with FID and the application of these techniques. 

Figure 1 Scheme showing the working principle of the tubular TLC-FID scanner. (Reproduced in part from Ref. 14 with permission of Elsevier Publishing Co., Amsterdam, The Netherlands.)... 

Before using the coated rods for analysis they must be meticulously cleaned free of any organic matter that produces signals in the FID. This is done conveniently, in a similar manner as in tubular TLC, by driving the rods through the flame jet of the FID in the TLC scanner (Figure 2). 

Similar considerations concerning the choice of the developing solvents and the precautions to be taken in order to prevent contamination by foreign organic matter apply to coated rod TLC as to tubular TLC. Reusability of the Chromarods is excellent provided proper care is exerted in their handling and storage as indicated in supplier s manual and in a monograph (16). 

The tubular TLC-FID systems have been used so far mainly for the analysis of lipids and related substances listed in Table 1. In this context it should be of interest to note that tubular TLC systems have also been coupled with vapor phase radiation detectors (2,9) and with a mass spectrometer (31,32). 

Toxopherols. See Lipophilic vitamins, vitamin E Triacetylcellulose thin-layer plates, enantiomeric separation on, 630-631 Triazines, 774-779 Troleandomycin, 463-468 Tubular TLC-FID systems, 362-364 applications, 365... 

---