This standard provides a method for the determination of trace monocyclic aromatic hydrocarbon impurities in toluene, mixed Xylene and p-Xylene by Gas chromatography, CG. It is mainly used to set product specifications and internal quality control. The method is capable of detecting total aliphatic hydrocarbons of 1 to 10 carbon atoms and monocyclic aromatic hydrocarbon impurities of 6 to 10 carbon atoms. Although the method is effective in analyzing impurities, there are limitations for the detection of absolute purity of unknown components. Note that the test results may have deviations from similar methods in Miscellaneous, so the results should be compared with caution.