Chromatography Forum

Hello,

I'm very new to chromatography and want to create a custom calculation to calculate the standard agreement between two standards in my sample set. the calculation we use is
(WS-std1 area/CS-std2 area)x(CS-std2 wt/WS-std1 wt)x100

How would I set this up in empower

This is very easy to set up and just requires certain labels in your sample set. Label the working standard as WS and control sample as CS, and in your processing method under CConst1 and CConst2- put the control sample weight value into CConst1 and the working standard weight into CConst2.

Then create a peak, real custom field, search order Result Set Only, Peak and Sample Type set to All, and the formula is:

(WS.%.(Area)/CS.%.(Area))/((CConst1/CConst2))*100

Then process a sample set to generate a result set and your result will appear in the result set.

Okay that makes sense. So if i have multiple of each type would i just calculate the avg by typing
(WS.%.AVE(Area)/CS.%.AVE(Area))/((CConst1/CConst2))*100

Hello,

By Multiple of each type, do you mean multiple injections of the WS and CS? If so, then yes you have to add in AVE but there needs to be 3 dots in the formula, so it becomes:

(WS.%..AVE(Area)/CS.%..AVE(Area))/((CConst1/CConst2))*100

Also, add the function Summarize Custom Fields as the last line in your sample set (you need this because of the AVE function in formula) and make sure the Processing column for this function is set to Normal and not Dont Process or Report. Then process a sample set to generate a result set and the result will be calculated in your result set.

Got it. Thanks! So i Can understand, why is the naming scheme the way it is? I.e the 3 dots and such.

Its to do with the syntax that Empower requires between an intersample calculation without summary, such as Std.%.(Area)/Control.%.(Area) and one with a summary for example Std.%..AVE(Area) or Control.%..MAX(Height). 2 dots no summary 3 dots with summary. There is a lot of background information on custom fields which explain this better. If you google Empower 3 intersample custom fields you will get a lot of slide packs which explain this very well and will be helpful to you when you create custom fields for your laboratory.