Preparative chromatography equipment

In industry and academia the need often arises to isolate portions of a polymer sample, whether it be to separate low molecular weight material from a sample or to actually fractionate the polymer across its molecular weight distribution. If gram quantities of isolated polymer are needed, true preparative chromatography equipment and techniques are usually necessary. 

A second field of rapid development in the l.c. of carbohydrates is in practical, preparative chromatography. Early preparative systems used large, expensive columns with low resolving power, and hence, were not extensively applied in carbohydrate research. New research is showing that various carbohydrates can be separated on the gram scale, using normal l.c. equipment and large columns home-packed with relatively... 

Preparative chromatography should always be carried out in well-ventilated areas. When using large amounts of electrostatic solvents, e.g., hexane, care should be taken to ground equipment and prevent fires due to electrostatic discharge. Heptane is safer than hexane (seeTable 5.3). 

Gas chromatography equipped with a flame ionization detector (FID) and quadrupole MS have been employed for measuring carbon disulfide concentrations in the breath of workers following exposure to carbon disulfide (Campbell et al. 1985 Wells and Koves 1974). The MS technique is rapid and requires no sample preparation (Campbell et al. 1985). A detection limit of 1.6 ppb (5 pg/m3) of... 

The above two optimization approaches have different effects on the cost of preparative chromatography. Efficiency is increased by decreasing the particle diameter of the stationary phase. However, then the costs of the phase rapidly increase, along with the costs of the equipment, which needs to be more pressure-stable for operation with smaller particle diameters. It is, therefore, worth looking for systems with optimized selectivities. 

The purpose of this chapter is to discuss equipment for preparative chromatography in general and to outline additionally aspects that are typical for the separation of fine chemicals and low-molecular-weight products as well as the separation of biopolymers like proteins. 

Analytical systems do equip almost all laboratories. Many different kinds of particle sizes are used from 20 to 2 [tm (from HPLC to UPLC), using liquid or supercritical fluid mobile phases. An intermediate market is to be considered using 10 mm ID columns for small-scale purifications. The term preparative chromatography is dedicated to purification units using column diameters from 50 up to 1600 mm ID. 

A chromatography equipment is quite complex and many technical failures may happen when operating a preparative device. Most of the time, a technical problem is directly visible or even detected by the system if this one is automated. 

These techniques do not differ only in terms of accuracy and experimental effort. Their application is also limited by the availability of the required equipment. Not all methods are suitable for columns with low efficiency, because peak deformations will affect the isotherm parameters. The actual setup and experimental conditions should be as close as possible to the operating conditions for later production purposes. However, to save time and solutes, the column dimensions are usually only of smaller (analytical) scale, or semipreparative at maximum. Preparative chromatography requires typically the application of adsorbents, with larger particle sizes compared to analytical applications. In isotherm measurements temperature control is crucial, since adsorption may show significant temperature dependence. Sometimes the costs of solutes prohibit the use of methods that need larger amounts of samples. 

Fig. 8. Preparative Anion Exchange Column Chromatography Equipment...

In a comparative study we found that yields of a 100 amino acid-long protein purified with probe 2 are 5-15% and about 10-times those from a conventional multistep purification scheme (13). Under optimized conditions, the entire process of derivatization, cleavage, semi-preparative purification, fraction analysis, probe removal, and further semi-preparative chromatography requires about one week using standard laboratory equipment. 

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