Hinge Point Gradient Development

If neither binary gradient nor three-solvent isocratics are successful, some systems will next try to perform a three-solvent gradient optimization. This development is very difficult to visualize. Assuming simultaneous optimization of %B, %C, and flow rate hinge points, it takes a long, computation-intensive time to carry out. It would be nearly impossible to carry out manually. The key is continually to use the rule of one change only one variable at a time and to carefully select limits for evaluation. 

These last changes are probably of academic interest only. Most separations can be achieved nicely with either a two-solvent isocratic or a binary gradient. 

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Figure 12.5 Gradient methods development, (a) Initial gradient (b) hinge points adjustments.

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