I'm not sure if I understand your question. Are you trying to determine the amount of the constituent in your sample based on peak size in the GC/MS profile? If that is the case, all you need do is to run a series of standards of the pure constituent on the instrument, then have the instrument's integrator measure the peak sizes for each constituent concentration. From this, you can prepare a calibration curve (amount vs. peak area). You can then determine the amount of the constituent in your test sample by reference to the calibration curve.