To maximize standard accuracy, it is highly recommended that you calibrate with methane for
the flame ionization detector and isobutylene for the photoionization detector. Almost all
published response factors for FIDs and PIDs are based upon methane and isobutylene,
respectively. By employing a multipoint calibration for these compounds, you will improve the
accuracy of each detector over the entire dynamic range. Response factors/curves can then be
employed for correcting the detector’s response to different compounds. However, once a
multipoint calibration has been employed, any response curve must characterize only the relative
response at each concentration, excluding curvature of the calibrated compound. Thus ,
use of both multipoint calibration and response curves at the same time is difficult, and is not
recommended.