Preparative chromatography method development

Integration of sample preparation and chromatography by on-line coupling aims at reduction of analysis time. It is apparent from Section 7.1 that these hyphenated techniques are not yet contributing heavily to the overall efficiency of polymer/additive analysis in industry. On-line SFE-SFC requires considerable method development, and MAE-HPLC is off-line. Enhancement of sensitivity for trace analysis requires appropriate sample preparation and preconcentration schemes, as well as improved detection systems. 

Additional details of planar chromatography—methods of descending and radial development, how to prepare TLC plates, tips on how to apply the sample, what to do if the spots are not visible—and the details of preparatory TLC, etc., are beyond our scope. 

Developing an isolation approach is an activity that is frequently overlooked or addressed as an afterthought. However, solubility and stability data may dictate the development of a chromatographic method that requires the elaboration of the isolation, that is, it is more complicated than a simple evaporation of the mobile phase. The development of the chromatographic process should be linked to and interactively codeveloped with the isolation. Ideally, the isolated impurity sample should not contain other compounds or artifacts, such as solvents, mobile-phase additives or particulate matter from the preparative chromatography, as they may interfere with the structure elucidation effort or adversely affect the stability of the impurity during the isolation process. Therefore, it is preferable to avoid or minimize the use of mobile-phase additives. However, should this prove to be impossible, the additive used should be easy to remove. The judicious choice of mobile phase in the HPLC process increases the ability to recover the compound of interest without or with minimum degradation. The most common... 

Osmotic effects play an important role mainly at high injected polymer concentrations. They may selectively affect the retention volumes of smaller polymer species contained in the polymer sample [97], Osmotic effects within porous column packings form the basis of interesting preparative liquid chromatographic method developed by Teraoka and coworkers [98-101] and denoted the high osmotic pressure liquid chromatography. 

You need to decide the goal of an analysis before developing a chromatographic method. The key to successful chromatography is to have a clean sample. Solid-phase microextraction, purge and trap, and thermal desorption can isolate volatile components from complex matrices. After the sample preparation method has been chosen, the remaining decisions for method development are to select a detector, a column, and the injection method, in that order. 

As in gas chromatography (Section 24-5), the first steps in method development are to (1) determine the goal of the analysis, (2) select a method of sample preparation to ensure a clean sample, and (3) choose a detector that allows you to observe the desired analytes in the mixture. The remainder of method development described in the following sections assumes that steps 1 through 3 have been carried out. 

Chi is purified from chloroplast extracts, usually obtained from spinach leaves, by dioxane precipitation method (51) and conventional sugar column chromatography (52). For rapid and easy preparation, the method recently developed by Omata and Murata (53) is satisfactory synthetic (DEAE-) Sepharose is substituted for sugar on the column. Besides using spectroscopic criteria (52), the purity of Chi samples can be checked readily by means of silica-gel thin layer chromatography (54). Colorless contaminations in Chi... 

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