Program Wizard/PGM Editor/Flow System - <Timebase>:
Flow/Gradient Options/Multi-Step Gradient

Create user-defined flow and/or % Gradient profiles. The resulting profile is graphically represented.

 Tips: 

The Dionex GP40/GP50, GS50, IP20/IP25, IC20/IC25/IC25A, and IS25 pumps do not deliver flow gradient ramps. Instead, changing the flow rate between one time value and the next immediately changes the flow rate (step change). (Also, see Practical Tips for Device Control  Pump and Flow Control.)

If input fields do not contain a value in the PGM Editor, the related property or command is not explicitly set in the current PGM File. In this case, the previously set value applies for the entire program.

Entering gradients

• Retention – Enter the time (relative to the injection time) of the flow value and/or % value modification.

• Flow – Enter a value in this column, if the flow rate is to change at time t.

• %B, %C, %D – Enter a value in these columns, if the amount of the delivered solvent B, C, or D should change. %A is the difference between the total of the entered values and 100%.

• Curve – Some Dionex pumps support the Curve command: Enter a value to determine whether the pump delivers a linear or curved gradient (see Gradient Curves). Curve 5 (the default) is linear; curves 1 - 4 are convex upward and curves 6 - 9 are concave upward. Chromeleon also supports the Curve functionality for the pumps of the Shimadzu LC-2010 HPLC system. Type the required curve value into the column. Available values are Linear, Convex1–Convex10 and Concave1–Concave10. For details, also refer to Shimadzu LC-2010 HPLC System: Setting Gradient Profiles.

• Insert Line –Adds another line to the table. After the first insertion of a new line, further lines are automatically added. Enable and disable the option with the Autom. Append New Lines command on the context menu. (Note: To open this context menu, right-click in a table.)

• Press the <arrow-down> key on the keyboard to append a new line to the end of the table.

• Delete Line – Removes a line from the table.

• The red coloring in a cell indicates an invalid entry. Correct all invalid entries before closing the window.

• Clean Up – Removes superfluous entries from a previously selected area.

• Invert – Creates an inverse of the analytical gradient of the left pump ('PumpLeft') if a gradient was defined for the analytical pump ('PumpRight') in the PGM and one of the following UltiMate 3000 pump modules is used: DGP-3600RS, DGP-3600SD or DGP-3600BM. Additionally, you can define a delay time for the flow of the inverted gradient to compensate for the time needed by the flow of the analytical gradient ('PumpRight') to pass the column. For further information, also refer to Defining an Inverse Gradient (UltiMate 3000 DGP-3600RS/SD/BM).

   Note: 

  When an inverse gradient is created, the gradient that was defined for the left pump (PumpLeft) will be discarded and replaced by the inverted gradient.

• Interpolate – Calculates missing values between two or more time values. The values are automatically added to the table.

• Select Fill Column on the context menu (or press the F9 key) to fill the cells in the column with the currently selected value. Only the cells below the selected value are filled.

Graphical representation

Each flow and solvent value of the value table is represented as a dot in the graphic. By interpolation between the basic points of a column, an area gradient profile results.

The solvents are displayed in their respective legend color. The flow rate is indicated as a narrow colored line. In Tandem Operation mode, a vertical red line indicates the reconditioning start time.

 Tip:

Try to avoid editing programs for Tandem Operation. If editing is necessary, keep in mind that you have the make the corresponding changes also for the other pump. Any inconsistencies that might occur are displayed on the Consistency Check page. (When Chromeleon detects inconsistencies, this page opens automatically when you exit the PGM Editor and specify that you want to solve the problem(s). As an alternative, you may open this page by clicking the x2 Tandem Operation icon.)