Column packing, cost

Table 6.3. Cost of column packing. Cost basis mid 2004 ...

Time, Cost, and Equipment Analysis time can vary from several minutes for samples containing only a few constituents to more than an hour for more complex samples. Preliminary sample preparation may substantially increase the analysis time. Instrumentation for gas chromatography ranges in price from inexpensive (a few thousand dollars) to expensive (more than 50,000). The more expensive models are equipped for capillary columns and include a variety of injection options and more sophisticated detectors, such as a mass spectrometer. Packed columns typically cost 50- 200, and the cost of a capillary column is typically 200- 1000. 

A third parameter to consider is the column construction. Thus the sample applicator should provide optimal sample application to give the most performance possible out of the packed bed. Constructions should also allow simple, fast, and reproducible packing of the column. Because costs for repacking of columns are a substantial operating cost item in industrial chromatography, the selection of column construction from this point of view is also important. Some novel column constructions allow very simple procedures both for laboratory and for industrial scale (e.g., INdEX columns, see Section V). 

Few laboratories have developed their own facilities for packing conventional and small bore columns, preferring to rely on commercial manufacturers for their needs. This is understandable since packed columns containing any common phase can be obtained at an acceptable cost and with a guarantee of acceptable performance and stability. Column packing generally requires access to equipment not readily available in all laboratories and... 

Cost of solvent extraction auxiliaries Cost of absorbtion and distillation column packing, supports and distributors Cost of tanks (surge, etc.)... 

Fast gradient separations can be achieved, at a cost of decreased peak capacity, by using short packed columns and simultaneously decreasing the particle size, dp, of the packing material to keep a constant ratio of the column length to the mean particle diameter, lidp, e.g., with a 3 cm column packed with a 3 [im material, or even a 1 cm, 1 pm column for very fast separation instead of a conventional 5 cm, 5 pm or a 10 cm, 10 pm column. At constant Vq/V , and Hdp ratios, the... 

In recent years h.p.l.c. has become a valuable chromatographic tool for analytical and preparative scale work. In this latter area the separation of isomers (structural, diastereoisomeric, and enantiomeric) has been possible by the selection of appropriate column packing material and solvent systems. However, the equipment, operating costs, and column packing materials are more expensive than those in t.l.c., g.l.c. and conventional liquid-solid column chromatography. 

Column packing is as much art as it is science. Even the professionals in the held cannot routinely prepare columns that will give the same plate count column to column. They quality control the columns with a set of standards, and columns that deviate by more than a set amount are either dumped and repacked (not cost effective) or are sold as specialty columns. Columns that exceed QC specifications are almost as bad as poor efficiency columns ... 

Figure 8.7 provides fractionation column internal trays that are to be added to the overall pressure vessel cost. A packed-column internal (random packing) cost is also given as cost per cubic foot of column-packed volume. 

Since the samples run in prep LC are often very crude, it is to be expected that the column packing will become contaminated with chemicals that did not elute. Cleaning can be accomplished with polar solvents like propanol or ethyl acetate (for normal phase systems), or the packing can simply be discarded. The latter alternative may be cheaper, considering the cost of solvents and waste disposal. 

The packing cost, Cp, is a function of the packing volume, Vp, which is in turn a product of the packing depth, Hp, and column cross-sectional area, Ac ... 

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