Fingerprinting chromatograms

Advantages and disadvantages of HS-GC over regular GC are summarised in Table. 4.26. HS-GC fingerprinting chromatograms obviously include only the volatile components present and do not provide a complete picture of sample composition on the other hand, when solvent extraction is used, all the soluble sample constituents are removed, including also those having no appreciable vapour pressure at the equilibration temperature. Headspace analysis enhances the peaks of volatile trace components. 

Jeltes and Van Tonkelaar [20] investigated problems of oil pollution, the nature of the contaminants and the chemical methods used for their detection. In particular, the use of gas chromatography to obtain fingerprint chromatograms of oil pollutants in water, and of infrared spectrophotometry to determine the oil contents of soils and sediments, is discussed. 

It is well known for example in the saturated LDPE polymer chains that a certain number of double bounds exist which can be measured with IR spectroscopy. By extraction with non-polar solvents and GC separation, numerous alkanes and alkenes can be identified which are dissolved in small concentrations in the PE. The odor thresholds of these compounds are in general so high that these hydrocarbons play no sensory role. As a result no correlation can be made between the total amount of volatile compounds isolated from PE or the fingerprint chromatogram from a GC separation and the sensory properties of a sample. The relevant sensory compounds as a rule are the (order of magnitude) less concentrated oxygenated compounds in the... 

Following the separation of pyrolysates, the detection can be done using common procedures for GC such as thermal conductivity detection, flame ionization detection (FID), etc. However, nonselective detectors without the identification capability are less common than mass spectrometric detection. While a GC separation with FID detection can provide only a fingerprint chromatogram for a specific polymer pyrolysate, mass spectrometry allows, at least in principle, the identification of pyrolysate components. 

Most of the alphatic fractions were separated into normal and branched alkane fractions after the removal of unsaturated hydrocarbon. Most of these subfractions were analysed by GO to give fingerprint chromatograms. These analyses were used to provide data that allowed carbon preference indices, pristane/phytane ratios etc. to be measured. Also, the relative amounts of (17 H, 21/ H 17/3 H, 21 oCH and 17 H, 21(3 H) hopanes, steranes, 4-methyl steranes, carotenoid and other related compounds were assessed from gas chromatograms and reconstructed ion chromatograms. A large number of Kovats Retention Indices (0V-101) were measured and tabulated for these compounds also (10). 

Identity tests, qualitative determination of relevant substances of the plants (e.g. fingerprint chromatograms). 

If an herbal medicinal product contains several herbal drugs or preparations of several herbal drugs and if it is not possible to determine the stability of each active substance, the stability of the medicinal product should be determined by appropriate fingerprint chromatograms, appropriate overall methods of assay and physical and sensory tests, or other appropriate tests. The appropriateness of the tests should be justified by the applicant. 

As the herbal substance or herbal preparation in its entirety is regarded as the active substance, a mere determination of the stability of the constituents with known therapeutic activity will not suffice. The stability of other substances present in the herbal substance or in the herbal preparation, should, as far as possible, also be demonstrated, for example, by means of appropriate fingerprint chromatograms. It should also be demonstrated that their proportional content remains constant. 

Fig. (I). HPLC fingerprint chromatogram of a hydroalcoholic extract of St. John s Wort...

R 672 Y. Zheng and F. Wu, Advanced Studies on Fingerprint Chromatogram of Traditional Chinese Medicine , Tianran Chanwu Yanjiu Yu Kaifa, 2003,15, 55... 

Fingerprint chromatograms obtained by LC coupled to one or more detectors can be considered as characteristic profiles that together reflect... 

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