3 Replies Latest reply on Jun 7, 2018 1:55 AM by wydnaa

    Response Factor Calculation

    okolade

      Hello again,

      I had some questions regarding how the response factor is calculated within the OpenLab Chemstation software. I am utilizing the Agilent GC 7890A and whenever I run a sequence the response factor either comes out the same for every run or two numbers will be the same for a sequence with 6+ runs. Using the response factor formula,

                     R = (Area of Compound)/(Area of ISTD) * (Concentration of ISTD)/(Concentration of Compound)

      I was able to calculate the factors manually. The results I got had variation between runs and were entirely different values than the ones produced by intelligent reporting. After trying this, I used the "Compare two Compounds" Option and created a column for each of the variables above. I then created a new column that would directly calculate the response factor using the set and defined variables. The answer it produced was still the same number. For 21 runs of 7 different samples with different areas and concentrations, the response factor was completely identical. I've included some images below, but does anyone know why the software is producing the same number for different runs?

        • Re: Response Factor Calculation
          ryoboyle

          Hello,

           

          I added tags to your post to increase visibility.

           

          The different quantification calculations that OpenLAB ChemStation employs are outlined in the Reference to Operation Principles manual. This manual can be found on disk 2 of your installation media, or at the following link: https://www.agilent.com/cs/library/usermanuals/public/CDS_CS-references.pdf . The section on quantification begins on page 81 (section for the ISTD quantification mode begins on page 90).

          • Re: Response Factor Calculation
            ir_nerd

            Hi Okolade,

             

            Am I guessing right if I suppose you saved your ratio:

            R = (Area of Compound)/(Area of ISTD) * (Concentration of ISTD)/(Concentration of Compound)

             

            in a variable ?

            If yes, you have to consider that in Intelligent reporting a variable can only contain one value. If for example you want to save one variable "Ratio" for each of your peak,

             

            If you save the variable as following:

            Then, when you recall the variable, you will always return the last value which was saved for this variable.

             

             

            If you want to save your variable for each of your peaks. You would need to save it with a unique key value, such as Peak_ID:

             

            In that case you save one value for each peak, and if you recall your variable, every peaks will have its own value.

             

             

            PS: To modify your variable. You will need to remove all expression that uses your variable in every fields where you used it. Then click "report properties", and in the variable tab, delete the variable. Then recreate the variable using the unique key value.

             

             

            Regards,

            Pierre

            • Re: Response Factor Calculation
              wydnaa

              Is your Response Factor column a custom field, in which you are calculating the response factor or is it showing the response factor from the calibration table in your method?  The latter would make it the same for every sample.

               

              /Andy