Dear Ezealisjii,
In my opinion, it is better for you to use the internal standard (IS) for analyzing drug concentration in pharmacokinetic study because there are some extraction procedures. You will need the internal standard because it can be a correction factor when you calculate the concentration, so you will not calculate the area, but you will calculate the peak area ratio (PAR) between the drug and IS. PAR is used for making calibration curve.
Calibration curve is required to calculate the concentration and content. While internal standard is added to to remove zero errors.
Calibration curve is required for both the external standard and internal standard procedure. Please see the link below which explain you in brief with example.
http://www.chromatographyonline.com/when-should-internal-standard-be-used-0
Yes calibration is required for both Internal & external standards
Big thanks to all of you, the points are very much clear now.
Hi Kenneth, the internal standard is used to calibrate the errors from experiments (pipetting, extraction process...) and instrument responses. If you want to do relative quantification (to compare the concentrations among your samples), you don't have to use calibration curve. But if want to know the absolute quantification of your interest compound, the calibration curve is necessary then.
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