# Auto calculate calibration amount in Openlab CDS

Hi,

I am setting a method in OpenLab CDS where the ISTD (calbration) amount is different for each run. I am wondering if it is possible if we key in the ISTD weight in the sequence table, and the amount could be auto-calculated when I review the chromatogram?

C23:0 is the ISTD and would be spiked into each sample, hence the amount spiked in would be different for each run. The amount of C23:0 =  ISTD amount / 25

Thus my question is, is it possible to let the software auto calculate the amount of C23:0 (which will change the Level amount automatically for each run), by entering the ISTD amount and multiplier?  • Hi

What does your sequence look like?  How do you create the calibration?

What I see from your screenshots doesn't look like ISTD calibration, but a calibration using C23:0 as a reference.  I may be missing something Kindest regards

Andy

• Hi Andy, sorry, it should be more of a one point external calibration, and other curves are referencing to C23:0. Not sure if this is the correct way to create, but most of our methods are created in this way.

Technically there are four compounds to be measured, which are compound 2,3,5 and 6 in below table and the sum of these four compounds will give the result for Total PUFA. Compound 4 is the standard where we spike in for each sample. We would run the sample as calibration standard and clear all calibration every time. Before we run, the sample amount and ISTD amount is keyed in the table. Currently, all multipliers and dilution factors are set as 0. In this case, is there a way to auto-calculate the amount for Level 1 in the first picture by taking the ISTD amount we entered divided by 25.?

• I can't think of a way to do exactly what you describe, but I'm sure that a custom calculation of some sort might achieve the same result.

Kind regards

Andy

• Hi Key, have you found the answer for your question? I am having the similar problem. Right now I am processing the results after completing the sequence. It would be great if I can put the standard concentration before starting the sequence. Thanks

• Hey Kris, I tried doing custom calculations but I could not find the correct parameter to get the correct value. Currently I am still doing manual correction after the sequence has completed.

• Hello,

If you are just trying to change the ISTD concentration you can do that for each injection of the sequence in the table. You may need to turn on the correct columns in the sequence. You can also change external standard values if needed in the sequence for your calibration injections. This can be done in the compound amounts tab if you have a processing method selected.  • Key,

You would probably need to do this calculation with compound custom fields or constants since the multiplier is no accessible in custom calculator. You could use the sample amount and a sample custom field for the C23:0 RF calculation and then use that to calculate the other peaks with the correction factor from the constants file or compound custom fields.

Marty

• Hi Martin, your reply is really useful. Thanks. Once I loaded my processing method, the compound amount is enabled. I am confused with the unit for "amount in sample" and "amount in method".

I have one point calibration standard at 0.1 ug/mL. Should I put 0.1 in the "amount in sample? I cant enter the "amount in method", so should I put 1 in processing method? Thank you :)

Regards

• Kris,

Amount in method is the amount for that level from your method calibration table. The amount in sample is the compound amount in the current injection for the standard level selected. Lets say you calibrate frequently and use the actual weights for your standard as the calibration amounts and thus need to update the method calibration table.  This feature allows you to override the values in the method directly from the sequence so you do not have to update the calibration in the processing method directly.

• Thanks Martin. 