Calibration curve - factor dilution

Question

Hello everyone, 
 I am quite new to Open Lab CDS 2.5. I made a calibration curve using an ISTD in order to calculate the concentration of my compound. However I feel like my calibration curve is not constant one day to another, I can have more than 1 mg/ml deviation. 
 If I look on chromatograms, I do not have variation of response, so I am wondering if my issue is coming from the data I fill in the sequence. 
 
 For each analysis, I weigh 200mg of my compound solution (20g/L) then I add 200&micro;L of ISTD (10g/L) and I complete with solvent to 10ml. 
 For example : 
 I fill in the exact mass of my compound solution (for example : 202.6 mg) on sample amount box, I fill in the exact volume of my ISTD (200&micro;L) ISTD amount and I also add an dilution factor 0.9872 (200/202.6). 
 Compound response : 92.255 ; ISTD response : 81.839 -> final concentration = 21.323 g/L 
 I repeat the operation with the same sample : 208.1mg on sample amount, 200&micro;L ISTD amount, dilution factor : 0.9611 
 Compound response : 91.996 ; ISTD response 83.530 -> final concentration = 20.280 g/L 
 Chromatograms overlay very well. 
 
 Is the dilution factor impact the ISTD ? What should I do ? 
 
 Thank you for your help

martin.adams · Accepted Answer

Hello, 
 
 Sample Amount is not used unless you have selected to do mass% calculation or are doing some kind of custom calculation utilizing sample amount. You compound weights and IS need to be in the calibration table of the method. If you change your standard weight each run you can enter it in by following the instructions below. You can find more details on your system in the OpenLab help and learning at the link below. 
 
 Marty Adams 
 
 file:///C:/Program%20Files%20(x86)/Agilent%20Technologies/OpenLabHelp/en/index.htm#t=mergedProjects%2FAcquisition%2FSet_compound_amounts.htm%3Frhhlterm%3Dcompound%2520amounts%26rhsyns%3D%2520 
 Set compound amounts in the sequence table 
 You can set up the sequence table to ignore the calibrator compounds defined in your data processing method. The new values entered in the sequence table will be used by the processing method to construct the calibration curve. 
 
 Create a sequence with the Data Analysis processing method. 
 Click Show column chooser . 
 Select Compound amounts , and click OK . The Compound amounts column appears in your sequence table. 
 Click a cell in the Compound amounts column. The Compound amounts window opens below the sequence table, displaying the compounds and amounts defined in the processing method. 
 For each compound where you want to use a different amount, enter the new value in the Amount in sample column. 
 
 After the data is acquired and processed, the new values are used to create the calibration curve and calculate results for the run. The new values can be viewed in the Injection List window of the Data Analysis program.

Calibration curve - factor dilution

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