Check the column performance

If you installed the 2D-LC Add-on, and you check the system suitability values for a ²D column: Use the transfer time as the void time that you enter in the column parameters. See 2D-LC help for details.

This procedure describes how to adjust the void time and length values used to calculate the column performance. Starting with OpenLab CDS 2.5, you configure these values individually per column.

Prerequisites

• Use a processing method configuration that includes system suitability parameters.

• To be able to carry out the procedure as described, you need the privilege Processing Method > Edit system suitability parameters. Privileges are configured in the Control Panel.

• If the project enforces method approval, the method status must be Generic. For details, see Method approval.

1. In the processing method, select the System Suitability > Properties node.

2. Under Separation performance computation, select the following values:

   Column performance:	Select All peaks.
   Tangent calculation mode:	Select Standard for backward compatibility with results generated with OpenLab CDS 2.5 or lower. With very noisy data, the application may not be able to calculate the number of plates. Select Advanced to use more data points for the tangent calculation. Use this option especially for very noisy data.
   Pharmacopeias:	Select the required pharmacopeia or pharmacopeias.

After selecting a pharmacopeia, the application lists all detectors used in any loaded injection in the column dimensions table.

If column information has been specified in the acquisition method, it is automatically added to the table. By default, the length of the columns is the same as shown in the Acquisition Setpoint (Column parameters tab or Overridden column parameters tab).

For LC systems, the void time needs to measured by determining the retention time of an unretained peak. It can be approximated by dividing the column dead volume (shown in the Acquisition Setpoints window/Column parameters or Overridden column parameters tab) by the pump flow (shown in the Acquisition Setpoints window/Acquisition parameters tab).

If you use a method that has been created with OpenLab CDS version 2.4 or lower, and you have overridden the void time and column length in that method, your new values will be used in the column dimensions table.

3. Check if the correct columns are connected to the correct detectors.

Click in the Column name field, and select the correct column as required.

Select Custom values if no column parameters have been saved during acquisition, or if you need to use different values.

4. For columns with custom values, provide the void time, length, and length unit as required.

5. Reprocess the injection.

The column performance is calculated using the values from the column dimensions table.

6. In the Injection Results window, display the following columns as required (click the Column Chooser symbol in the top left corner to show hidden columns):

   • Asymmetry 10%

   • Capacity factor

   • Plates (EP, JP, USP)

   • Plates pm (EP, JP, USP)

   • Resol. (EP, JP, USP)

   • RRT EP

   • Selectivity

   • Symmetry

   • Tailing

   • Width (10%, 5 sigma, 5%, 50%, tangent)

Selectivity and resolution are not measured for the first peak in a chromatogram because there is no preceding peak to use in the calculation.

For details on the calculation, see Performance test definitions.

See Also

• Override column parameters