[en] The experiment MACRO (Monopole, Astrophysics, and Cosmic Ray Observatory), located in the Gran Sasso Laboratory in Italy, will use approximately one million liters of liquid scintillator and will last for five to ten years. We have developed a simple test for the MACRO experiment that determines the concentration of pseudocumene in its scintillator. This test has general applicability for a content analysis of volatile components in any liquid scintillator. (orig.)