Different Types of Related Substance Analysis

Area Percent.In this approach, the level of an individual related substance is

calculated by the following equation:

%related substance =area related substance/total area× 100%

where the area related substance is the peak area of the individual related substance

and the total area is the peak area (i.e., response) of the drug substance plus

the peak areas of all related substances. This is one of the simplest approaches

for related substance analysis because there is no need for a reference standard.

This is particularly important during the early phase of the project when a highly

purified reference standard is not available. It is the preferred approach as long

as the method performance meets the criteria described below.