Solvent gradient profile

Fig. 4.3b. Possible gradient profiles showing the blending of solvent...

The fractionation column is operated at conditions effective to form a precipitate on the support. The temperature of the column is lowered to a temperature less than about 40°C at a rate of l-0.5Khr 1. The PE fractions may then be recovered from the fractionation column by displacing a recovery solvent/non-solvent mixture into the column. The relative concentrations of the solvent and the nonsolvent are based on a solvent gradient profile of the PE parent polymer. The temperature of the column is raised to a temperature ranging from about the melting point temperature of the UHMWPE... 

Figure 25-13 Gradient elution of the same mixture of aromatic compounds in Figure 25-12 with the same column, flow rate, and solvents. The upper trace is the segmented gradient profile, so named because it is divided into several different segments.

Figure 10.9 HPLC trace of standard pigments using gradient elution system, (a) standard mixture (1) monitored at 415 nm (b) standard mixture (2) monitored at 490 nm and 590 nm. Conditions column 5 pm ( IS 150 X 4.6 mm, using diode array detection at 450 nm and gradient elution solvent A = 0.02 M ammonium acetate, Solvent B = acetonitrile gradient profile 0 min 95% A, 20 min 50% A, 25 min 95% A flow rate 1.0 ml/min.

A large number of unnatural a-amino acids are commercially available. Many of them are more hydrophobic than natural amino acids. To detect and clearly separate hydrophobic PTH-amino acids using the sequencer, we have extended the elution time from a total of 22 min to 28 min prior to washing the column with 90% solvent B (88% acetonitrile/12% isopropanol, v/v) (Table I). To use the existing software in the protein sequencer to read all 20 PTH-natural amino acids automatically, the first 18 min of the gradient profile is identical to that recommended by the manufacturer. This ensures that the elution profile of natural amino acids remains unchanged. 

Flask A should contain a teflon coated magnetic stir bar and be placed on a magnetic stirrer to ensure adequate mixing of the two solvents. This will provide a smooth gradient profile. Fill in the Vj volume in Activity A-6. 

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