Chromatographic fingerprinting

Data analysis is one aspect of multidimensional analyses that must be optimized in the future. The analysis of chromatographic data beyond one dimension is still exceedingly problematic, especially in the analyses of highly complex mixtures. Better software may need to be developed in order to analyze two- and three-dimensional peaks due to their complexity. Three-dimensional data is only useful today in terms of fingerprinting and often that even requires extensive data analysis. A great deal of research must still be carried out to make the interpretation and quantification of multidimensional data easier. 

Additional support for this suggestion came from a study of L. distichophylla J. Agardh collected off the northeastern coast of New Zealand by Blunt et al. (1984). These workers examined the sesquiterpene chemistry of plants collected at three depths (1) low intertidal to upper subtidal (2) mid-intertidal and (3) upper intertidal. Chromatographic fingerprints of the latter two collections were identical, but the profile of fhe deep-gathered planfs differed in botti ttie number of compounds... 

While earlier papers cited buffer systems or aqueous o-phosphoric acid to achieve satisfactory peak resolution, most recent investigations involved acetic acid or formic acid systems. " Representative examples are 0.2% and 1% HCOOH for betacyanins and betaxanthins, respectively, the latter requiring a lower pH for chromatographic resolution. Methanol or acetonitrile are most commonly used as modifiers, either undiluted or diluted with purified water at ratios of 60 40 or 80 20 (v/v), respectively. - Typical HPLC fingerprints for yellow and red beet juice are shown in Figure 6.4.1. 

Also, a chromatographic profile or fingerprint of trace unknowns can be established and monitored, so that if product performance unexpectedly changes, there will be a starting point for troubleshooting. The effects of experimental variables on sample recoveries should be measured directly by controlled variation of an experimental factor, using the reference standard, or suitable external standards, or spiked addition of an external standard to the reference standard. A detailed example of the use of internal and external standards is presented in Chapter 4. 

Figure 6 High-speed tryptic fingerprint. Horse cytochrome c was digested with trypsin and the peptide chromatographed in acetonitrile water 0.1% TFA at various temperatures and flow rates on a 15 x 0.2-cm PS-DVB column packed with 3-p, 300-A particles, (a) 26°C and 0.5 ml/min. (b) 42°C and 0.7 ml/min. (c) 70°C and 1.1 ml/min. Detection at 220 nm. Note that the resolution rises with the speed of separation.89 (From Swadesh, ]., BioTechniques, 9, 626, 1990. With permission.)...

Ehret-Henry et al. [220] have shown that H NMR spectra can be used without chromatographic analysis, to shorten the total identification time necessary, and as a fingerprint of all the extractable nonvolatile compounds present in food packaging material (safety control). Figure 5.10 shows a H NMR spectrum (in CDCI3 with TMS as internal standard) of a Soxhlet extract of a 35 pirn PP film (after solvent evaporation). The assignments of the resonances of Irgafos 168 and its decomposition products were confirmed by a 31P- H 2D correlation NMR experiment [220],... 

Electrospray (ESI) ionization mass spectrometry also plays in important role in bacterial characterization. Because it typically includes a chromatographic separation step, the approach is not considered as rapid as MALDI approaches, which do not incorporate a separation. However, compared to the times needed to grow bacteria in culture prior to analysis, the time frame is not lengthy, and the addition of chromatographic separation provides many opportunities to increase specificity. ESI/MS has been used to characterize cellular biomarkers for metabolic, genomic, and proteomics fingerprinting of bacteria, and these approaches are reported in two chapters. 

Otto M, Bandemer H (1986a) Pattern recognition based on fuzzy observations for spectroscopic quality control and chromatographic fingerprinting. Anal Chim Acta 184 21... 

The sulfur compounds that are present in minor quantities in petroleum products also exhibit a typical gas chromatographic fingerprint easily obtained by flame photometric detection. This fingerprint has been introduced to complement the flame ionisation detection chromatogram with the aim of resolving the ambiguities or increasing the reliability in the identification of the pollutants [74]. 

Interpretation/report The GC retention time of a naphthalene standard and the mass spectrum of this peak confirm its presence. Because of the complexity of the chromatograms of the petroleum products and the pesticide sample, you find it impossible to examine the chromatogram of each. However, a comparison of the GC fingerprints (i.e., the matching of chromatographic peaks and comparison of peak ratios) clearly shows that the sample consists of naphthalene dissolved in kerosene. 

The chromatographic results (fingerprint) of five hydrocarbon samples are tabulated in Table 4.8 and graphically illustrated in Figure 4.12. These LNAPL samples were... 

F. Gong, Y.-Z. Liang, P.-S. Xie and F.-T. Chau, Information theory applied to chromatographic fingerprint of herbal medicine for quality control. J. Chromatogr.A 1002 (2003) 25 40. 

Fig. 2.47. Chromatographic fingerprints from Rhizoma chuanxiong using gradient elution 1 (a) and 2 (b). Chromatographic fingerprints of a standard extract (c), one extract (d) and one product (e) of Gingko biloba at 360 nm. Peak 1 represents luteolin. Reprinted with permission from F. Gong el al. [147].

Furthermore, as a fuel evaporates or biodegrades, its pattern can change so radically that identification becomes difficult. Consequently, a gas chromatographic fingerprint is not a conclusive diagnostic tool. The methods used for total petroleum hydrocarbon analysis must stress calibration and quality control, whereas pattern recognition methods stress detail and comparability. 

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