Loading capacity, chromatography

Loading capacities in size exclusion chromatography are very low because all separation occurs within the liquid volume of the column. The small diffusion coefficients of macromolecules also contribute to bandspreading when loads are increased. The mass loading capacities for ovalbumin (MW 45,000) on various sizes of columns can be seen in Table 10.5. The maximum volume that can be injected in size exclusion chromatography before bandspreading occurs is about 2% of the liquid column volume. The maximum injection volumes for columns of different dimensions can also be seen in Table 10.5. 

Fast chromatography involves the use of narrow-bore columns (typically 0.1-mm i.d.) that will require higher inlet pressures compared with the conventional wide-bore capillary columns. These columns require detectors and computing systems capable of fast data acquisition. The main disadvantage is a much-reduced sample loading capacity. Advances in GC column technology, along with many of the GC-related techniques discussed below, were recently reviewed by Eiceman et... 

In preparative chromatography, selectivity and efficiency no longer have the same importance they do in analytical chromatography. A certain selectivity is required in preparative chromatography as everywhere else in order to achieve the separation, but other parameters are at least as important if not more so. These include the loading capacity of the stationary phase and the maximum speed (throughput) of the process. The three main economic criteria for a large scale separation process are... 

The loading capacity of SEC columns is quite modest compared to interactive modes of chromatography. A rule of thumb dictates that the sample volume capacity is about 2% of the column volume. A typical analytical SEC column with dimensions of 8 x 300 mm has a VM of 10 to 11 ml, providing a sample volume limit of about 200 pi. The mass loading limit for such a column is about 1 to 2 mg. Above these volume and mass limits, resolution will be compromised. Sample capacity will scale in proportion to column volumes for different column lengths and diameters. 

Analytical methods can be transferred easily to the preparative scale in polysaccharide-based CSPs, and these compounds have been used in preparative chromatography. Cellulose triacetate, which has good loading capacity, has been used for preparative separation at the industrial scale [70,85]. Moreover, the low cost of cellulose triacetate synthesis makes CTA ideal for preparative chromatography. 

What use would a practical handbook be if it did not tell you what you need and where to put it The guidelines given here are provided purely as an indicative potential of the capacity of a certain column size and the estimated footprint the column and its ancillary equipment will occupy. The capacity of the stationary phase will depend upon the mode of chromatography and the method of operation. For instance, the loading capacity of reversed phase and chiral stationary phases is generally at least half that of a normal phase media. This is not meant to imply that normal phase chromatography is more... 

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