ASTM D7504-23 "Standard Test Method for the Determination of Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas chromatography, CG, and Effective Carbon Number" is designed to determine the type and amount of hydrocarbon impurities that remain in chemical intermediates and solvents such as toluene, mixed Xylene, p-Xylene, o-Xylene, ethylbenzene, benzene, and styrene. This method is suitable for developing product specifications and internal quality control tools. Gas chromatography, CG, is used in the test to determine total non-aromatic and monocyclic aromatic hydrocarbons and to calculate the purity of each component. However, the test may not detect all components and unknown components may be present and need to be treated according to the Correction factor in practice. Use of this International Standard is subject to appropriate safety, health and environment practices and confirms the applicability of regulatory restrictions.