Preparing the Column

Based on the requirements of the separation, media of suitable pore size, particle size, and surface properties are selected as well as column dimensions and column material. In some cases a suitable combination of media type and column dimensions may be available as a prepacked column. In most cases, this is a more expensive alternative to preparing the column yourself but will provide a consistent quality as assured by the manufacturing and testing procedures of the vendor. The consistent quality may be critical in obtaining reproducible results and may thus be a cost-effective solution. Also, the fact that smaller particle-sized media are more difficult to pack and require special, and expensive, equipment has resulted in that gel filtration media of small particle size, e.g. smaller than 15 /zm, are predominantly supplied as prepacked columns. 

Conditioning the column. This step prepares the column to absorb the analytes and also pre-washes the column with the solvents that are used for the cleanup. 

Preparing the Column Compounds on the Column Visualization and Collection... 

System (1) has been adopted by the USP [71] for the assay of cortisone acetate and its official pharmaceutical formulations (either sterile suspension or tablets). The standard is prepared by transferring about 12 mg of cortisone acetate RS, accurately weighed, into a glass-stoppered 50-mL conical flask. 25.0 mL of internal standard solution is added, and the solution sonicated for 5 minutes. Approximately 1 mL of this solution is combined with 3 mL of mobile phase to obtain the standard preparation. The column is any 25 cm x 4.6 mm column that contains packing L3. The... 

The new chemistry is based on a Sr-90/Y-90 separation using a-hydroxyisobutyric acid (a-HIB) and cation exchange chromatography (5). Once the activities are loaded onto the column, the steps to prepare the column for the a-HIB elution remove several of the possibile contaminants including rubidium and cobalt. Finally, the a-HIB elution also removes a wide range of other elements as well, leaving strontium on the ion exchange column (6). 

The Amberlyst (NH4+) resin column is prepared as follows Amberlyst 15 (H+) (56 g, 100 mL dry, Rohm Haas Co.) is suspended in an open beaker containing methanol (100 mL). [Caution the slurry exotherms to ca. 40CC without external cooling, and expands to ca. 1.5 times its initial volume.] The slurry is poured into a 2.5 x 30-cm column and is eluted with 1 M methanolic ammonia (ca. 1 L) until a sample of the eluent diluted 1 1 with water is basic. The resin is then eluted with methanol (ca. 0.5 L) until a sample of the eluent diluted 1 1 with water is neutral. Once prepared, the column can be reused multiple times. 

Note that following any of the maintenance procedures listed above, reequilibrated the column must be to the original mobile phase, probably involving more time than would be needed for the normal change from water to the methanol solution routinely used to prepare the column for overnight storage. 

A carbon column was initially presented by Jensen and Sundstrom [137] for separation of non-planar and planar PCBs. It is often applied in the cleanup of PCDDs and PCDFs as presented by Smith et al. [138], Kuehl et al. [116] used a carbon-glass column to separate non-planar and planar compounds. They prepared the column by blending AMOCO PX-21 carbon (50 mg) with a shredded glass filter pad (600 mg) in dichloromethane and packed this slurry into a glass column. The sample was fractionated by eluting with dichloromethane (50 ml), dichloromethane benzene (1 1 50 ml), and finally in reverse with toluene (50 ml). Non-planar compounds, loosely bound planar compounds, and tightly bound planar compounds were isolated in these three fractions. PCDEs have been reported to elute in the same fraction as PCDDs and PCDFs on activated carbon [36]. 

Prepare the column sample by mixing 0.1 ml bromophenol blue (step 5-26) and 0.5 ml blue dextran solution (step 5-27). 

Prepare the column exactly as described above using activity III alumina. Then add a solution of 0.4 g of a 50 50 mixture of acetylferrocene (Caution toxic) and ferrocene that has been dissolved in the minimum quantity of dichloromethane, following the above procedure for adding the sample. 

The advantages of CLC are consequences of its miniaturization [9]. Due to its miniaturized size, it requires much less stationary phase than does ordinary HPLC and, as a consequence, more expensive phases can be used to prepare the columns. This includes chiral phases, experimental new materials, expensive biocompounds, and so forth. In the same way, the amount of mobile phase is very small, thus leading to a savings in buying, storing, and discarding the solvent, allowing... 

When washing is used for preparing the column for personnel entry, it is important to avoid trapping undesirable materials in valve bonnets, piping, and dead pockets. All valves should be opened, all dead pockets and valve bonnets should be flushed, and... 

Prepare the columns separately in a vacuum box. Sterilize the single inlets with 1% sodium hypochlorite or equivalent solution. 

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