Chromatographic analysis advantages

Several quantitative procedures for concentrations above 0.1 vol % are available. Gas chromatographic analysis (78) is particularly useful because it is fast, accurate, and relatively inexpensive. The standard wet-chemical, analytical method (76) takes advantage of the reaction between iodine pentoxide and carbon monoxide at 423 K. 

Of more immediate interest are approaches that permit offline TLC-MS in which the spots are scraped out from the layer and the analytes are either extracted from the sorbent to be transferred to the mass spectrometer as discrete samples or are introduced without sorbent removal into the spectrometer on a direct insertion probe (51). TLC-MS quantification and confirmation efficiency can be further enhanced by submitting the TLC extract to an additional chromatographic separation using a different technique prior to the final MS analysis. Advantages of this approach over direct TLC-MS include extra cleanup through the additional chromatographic separation (52). This has been realized in the TLC-GC-MS analysis of eggs and meat for chloramphenicol residues (49). 

In liquid chromatographic analysis of quinolone antibacterials, most popular is the fluorometric detector due to the inherent fluorescence of these drugs and the advantages in terms of selectivity and sensitivity that this detector offers (Table 29.6). Fluorometric detection after postcolumn derivatization with sulfuric acid has also been reported (203). However, quinolones exhibit also remarkable ultraviolet absorption and are therefore ideal for direct determination without derivatization. Detection can be performed in the wavelength range of 254-295 nm. 

To illustrate the advantage of this technique, compared either to direct chromatographic analysis of the water system or of an organic solvent extract, we may consider the circumstance of hexane as a hypothetical contaminant. This compound is distributed to the extent of 96% into the gas phase. The implications... 

The use fluorescence detection in the chromatographic analysis of biological matrices has found widespread applicability because of its inherent sensitivity and specificity (B25, H5, H7-H9, K23, K29, K32, Yl, Y2). Since fluorescence is more sensitive than UV spectroscopy, it can be used advantageously to analyze for naturally fluorescent compounds in the presence of nonfluorescing, UV-absorbing compounds. In such cases, fluorometric detection is more sensitive while at the same time possible interferences are eliminated. 

Figure 13 illustrates the use of spectrofluorometric detection in the reversed-phase chromatographic analysis of the control serum sample originally shown in Fig. 10. The advantages of fluorometric detection in eliminating background and increasing selectivity are obvious.

A procedure was developed by Hiatt (1983) and Dreisch and Munson (1983) to identify and quantify 1,1-dichloroethane in fish tissue samples by GC/MS, employing a fused-silica capillary column (FSCC) and vacuum distillation (extraction). An advantage of the vacuum extraction is that the system does not require elevated temperatures or the addition of reagents, which could produce unwanted degradation products (Hiatt 1981). The FSCC provides a more attractive approach than packed column for chromatographic analysis of volatile organic compounds, because FSCC can be heated to a higher-temperature (350°C) than that recommended for packed column thereby... 

It is dear that amine CDAs are highly useful in the chromatographic analysis of the enantiomeric composition of chiral carboxylic adds. Since such acids must also be derivatized (with a nonchiral reagent) for analysis on many of the available chiral LC columns, it would seem that the indirect method is advantageous and is likely to remain popular. 

A simple and fast method for identification of bifidobacteria using thin layer chromatographic analysis of short chain fatty acids in a culture broth is proposed (Table 1). This approach has many advantages the total time required to analyze organic acids is approximately 50 min and the identification protocol is simpler, quicker, and more economical than conventional identification methods. 

Figure 3. Relative sensitivity of a rabbit antibody to bentazon and methylated bentazon. A rabbit antisera against an N-derivatized bentazon had better recognition of methylated bentazon than bentazon. Coating antigens were Bz(6)-O-MPAA-BSA and Bz-succ-BSA for methyl bentazon and bentazon respectively. These curves indicate that one may find a much more sensitive assay for a derivative than for the parent compound. As in chromatographic analysis, it may be advantageous to run...

Ion chromatographic analysis methods ensure speed and high precision in the analysis of main components as well as of reaction and decomposition products in electroplating baths. The advantage of ion chromatography relative to the partly unspecific wet chemical methods utilized so far lies in the selectivity of the stationary phases and the detection systems being used. Thus, in most cases sample preparation is limited to a simple dilution with de-ionized water and subsequent filtration. A variety of applications on the basis of electrodeposition and electroless plating is summarized in Table 8-3. 

In the author s opinion, the use of PTH-derivatives for the separation and the identification of free amino acids, as a supplemental procedure to two-dimensional thin-layer chromatographic analysis, has no distinct advantage over the use of DNP-derivatives, but has a number... 

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