Obtaining Material for TLC and Sample Preparation

Marcel Dekxer, Inc. 270 Madison Avenue. New York, New York 10016 

Moreover, animals such as frogs, cockroaches, and snails are usually para- 

---

As indicated previously (see Section 1.2) pyrolysis must be associated with an analytical technique in order to provide information on a sample. Several common analytical techniques such as GC, GC/MS or GC/FTIR have been utilized either hyphenated with pyrolysis or off-line and were described previously. Less frequently, techniques such as HPLC, preparative LC, TLC, SFE/SFC, or NMR also have been used for the analysis of pyrolysates. These types of techniques are commonly applied off-line. They are used mainly for obtaining information on that part of the pyrolysate that is difficult to transfer directly to an analytical system such as a GC or for the analysis of materials associated with the char. However, the analysis of the non-volatile part of pyrolysates is frequently neglected, although this leads to an incomplete picture regarding the chemical composition of pyrolysates. 

TLC can provide other information critical in compound identification. Colors from selective chemical detection reactions, behavior in ultraviolet light, absorbance and/or fluorescence spectra obtained directly on the chromatogram by use of a spectrodensitometer or in solution after elution and Rp values of derivatives prepared by reaction before, during, or after development can be combined with the R p values of the sample to increase the degree of probability of correct identification [67,68]. Infrared (IR) and mass spectrometry combined with chromatography can provide unequivocal identification if sufficient sample is available. This is often not the case in trace analysis where nanogram amounts of material may be separated and detected by TLC, whereas microgram quantities are needed for conventional IR spectrometric confirmation of the trace substances. 

---