Preparative Chromatography - Preparative Chromatography Apparatus > Pumps > Page 24
The solvent reservoir is usually made of glass or stainless steel and should have an appropriate capacity, normally several gallons. Due to the large volumes of solvent that are often employed, the reservoirs should be closed and fitted with an appropriate 'breathing' device. In general, most of the parts of a preparative chromatograph are made from stainless steel, however for biologically sensitive, or labile substances, biocompatible materials may be necessary for certain parts of the apparatus. To fabricate the bulky preparative components (e.g. the column) from titanium that have sufficient strength can become inordinately expensive and plated base metal (e.g. using gold or some other suitable biocompatible metal) may be a more economic alternative.
The pump must have adequate capacity, and for columns up to 1 in. diameter, pumping rates of at least 150 ml/min. should be available. For larger columns, pumping rates of 500 ml to 1 liter per min. may be necessary. Owing to the limited strength of large diameter columns pressures much above 6000 p.s.i. are rarely required. Any glands involved in the pump should be made from appropriately inert material (e.g. 'Teflon' or 'loaded' 'Teflon', polytetrafluoroethylene,). In preparative chromatography, the sample is often placed on the column with a separate pump having its own sample reservoir, usually 1–2 l capacity depending on the size of the sample load and the solubility of the materials in the mobile phase. The required volume of sample is often placed on the column by pumping the sample solution at a known rate, for a defined time. In addition to the column and other parts of the apparatus, as the sample pump and reservoir may carry biosensitive materials, it may also need to be constructed of biocompatible materials.