How to calculate relative standard deviation

We have Empower 3 software. We use it to control Ion chromatography instrument. We have collected data. We would like to know, how to calculate relative standard deviation for the selected data (from injections,results, channels etc..). Is it possible directly or do we have to create a special template. If so kindly let us know the step by step procedure.


  • You can use either a report method or a custom field. Easier option is use a summary function in the report method. Select the data, right click Preview Publish, and use the option "Currently opened report method Untitled", which brings you to a blank page. Double click this page and you are into the properties. Because you want %RSD of several injections, then an Individual report isn't appropriate. Change to Summary By All. 
    Back in the report method, add a Peak table from the tree on the left, throw in whatever fields you need in the first tab (SampleName, Area, Amount etc) by selecting the appropriate category and double clicking to add to table, tick what peaks you require in the Peaks tab (Knowns, Internal etc), then in the Order By tab pick something like Channel ID and Retention Time ascending etc. Your Data Filter conditions should represent the data you want, is it only unknowns or standards etc. 

    Right click the column that you want %RSD on, for example Area, select column properties and double click the %RSD function on the tree on the left. This will report the %RSD of selected data, and you can pick the precision you want it displayed as for example 1 decimal place, 0 decimal places etc. 

    That should do it. Unless you need the stored %RSD value to calculate another value, the report is favourable over creating a custom field. 
  • Use same labels for injections of interest and process .

    Then in report use table properties and summary functions (see attached)

    Or Create a custom field but a bit pointless with report option

  • Thanks a lot for your support. Got it.
  • We also need one more support regarding system suitability results. We have checked USP system suitability summary results. It is showing RSD, however it is not showing peak tailing,resolution, capacity factor etc...Just blank column is appearing. Do we have to select options somewhere else ?. Or do we have to use any special software ?. Kindly help us.
  • Do you have the system suitability option ticked in the properties of the project? Right click the project< Properties, check the System Suitability option is ticked from the list on the left. 
    If it is ticked, do you have system suit ticked in the processing method- the "Calculate System Suitability Results" option at the top of the "Suitability" tab in the processing method. 
    Check in the Limits tab that you don't have the "Calculate Suitability Results" unticked next to your component(s). If this is not ticked, no suitability results will be calculated for these components. 
    Finally, is it just a case where you haven't added the field into the table in the report method?
  • Look at the Suitability tab of your Processing Method. I'm guessing something is not checked or filled out that needs to be.