Peak-shaving, preparative

The recycling techniques have been used for preparative chromatography using lower-resolution columns packed with larger particle sizes. The application is usually a binary separation. In this case, it is possible to extract the sides of the bands during each run to obtain the pure compounds. This technique is called peak shaving. The center of the band is recycled as usual. Thus the load on the column continuously decreases, and the width of the band can be controlled. With this method it is possible to obtain high-resolution prepara-... 

An additional example of the technique of recycling, which includes a procedure called peak shaving, is the preparative separation of the enantiomers of 5-methyl-5-phenylhydantoin. The recycling and peak shaving procedure is depicted in figure 12.8. The column was 30 cm long, 2 in. I.D., packed with 10 m particles carrying Vancomycin as the chiral stationary phase. The mobile phase was ethanol and the flow rate 100 ml/minute. The sample load was 400 mg dissolved in 5 ml of ethanol. 

This experiment will use the recycle mode to shave the peaks for purity as one would do in a preparative situation. 

Since the shaving technique is being used, this prepares the instrument for collection of the next peak. Refer to Figure 10-3. 

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