Sample preparation derivatization scheme

Automated injectors are often used when large numbers of samples are to be run. Most designs involve the use of the loop injector coupled to a robotic needle that draws the samples from vials arranged in a carousel-type auto-sampler. Some designs even allow sample preparation schemes such as extraction and derivatization (chemical reactions) to occur prior to injection. 

The earliest approach to amino acid analysis involved postcolumn reaction. This scheme offers several advantages compared to precolumn reaction. First, it simplifies the sample preparation necessary. Often, precolumn derivatizations require sample cleanup steps to eliminate sample... 

Thin-layer chromatograms are often subjected to various methods of detection for identification purposes. For this, the sample is apphed in a band several cm wide, up to a maximum of 18 cm, and the plate is cut up after development (see also Chapter 6 Derivatization ). Samples are also apphed at maximum width for preparative analysis. Special application schemes for two-dimensional TLC are shown in Section 4.3.2. 

Fulgides (e.g., 53, see Scheme 15) are capable of photochromic reactions. Yokoyama et al. reported the preparation and subsequent photochromic isomerization of a fulgide which was designed to resist enantiotopomerization [103]. A sample of the resolved fulgide was irradiated (405 nm light in toluene solution) and was observed to come to a pss with a ratio of 19 81. Irradiation with visible light (X > 580 nm) led to the complete recovery of the initial conformation. An advance on this system was made by the same authors, who described the process of diastereomeric photochromism, in which a fulgide derivatized with a binaphthyl auxiliary was allowed to thermally equilibrate, and a photocyclization process carried out [104]. As a result of the relative populations of photoreactive... 

After activation of dextran with different concentrations of CDI, DTPA NH2 was coupled to the activated dextran, as shown in the scheme of Fig 4. Four samples were prepared and, in order to obtain higher degrees of derivatization of the dextran with DTPA-NH2, the CDLdextran ratio was extended to 1.5. 

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