Dear Naziruddin

As said by Mr. Neshat, you can use the same calibration run for each sample. You can add another internal standard inside you sample if you want to see the stability of the sample too. But for the same compound, you can definitely use the same calibration run, with the same method.

Dear Naziruddin

No, It is not necessary to perform a calibration run for each sample. You can do it once and analyze all of your results.

Dear Naziruddin

As said by Mr. Neshat, you can use the same calibration run for each sample. You can add another internal standard inside you sample if you want to see the stability of the sample too. But for the same compound, you can definitely use the same calibration run, with the same method.

Yes and no.  Yes; The response factor of the detector for each molecule can be different.  No; the chemistry and structure are similar, therefore the response factor is similar.  However, you have to PROVE it!

Thank you for your answer Mr.Neshat, Mr.Mathieu and Mr.Bruce. I will do the calibration curve as suggested. 

Maybe Yes maybe No, it depends. If the the nature of the samples are not same, you need to validate it, for each kind of samples (urine, blood, tablet, capsule etc). Calibration curve must be performed for each series of analysis (maybe each day etc), If you turn-off the HPLC, you need to have new calibration curve. According to Eurachem 2014, to prove the used-method "still valid" for the routine  application, you need to inject QC samples  for every 20 samples (5 % of total samples), KInd regards

Based on your explanation, you can use one calibration curve of a compound (a styrene monomer) for all samples with the same method. The calibration curve should be obtained from intra-day and inter-day experiments at least three repetitions of each. Best regards.

According to ICH guidelines you have to prepare fresh samples. then only you can able to report and that is also minimum in triplicates.

Best Regards

You are better off using known addition as your quantification method when you have diverse matrices unless your prep method eliminates all interferences from the matrices (hard to prove up). Known addition will compensate for the changing matrices.

I am assuming your samples are in different matrices. If possible I prefer to build the standard to match the sample. If that is not possible then I like to do a standard addition. This is very important if solid phase extraction is being done. At the very minimum it is imperative to ensure that there are no interferences in the sample matrix.