The following two approaches are commonly used for quantitation of extractables:
Approach 1: An external authentic compound is used in a one-point calibration curve or a multi-point calibration curve. If an authentic compound is not available, a surrogate compound can be used
Approach 2: An internal standard is added to the sample. Relative response factors are then used for the quantitation of the extractable compounds. The relative response versus the internal standard is determined for each extractable compound in a separate experiment by using an authentic compound of each compound. If an authentic compound is not available, a surrogate compound of a similar structure can be used. If the structure of the extractable is unknown, an assumption can be made that the response of the unknown extractable is identical to the response of the internal standard, i.e. the relative response factor is assumed to be 1.