This method is for determining trace impurities in high-purity mixed xylenes by gas chromatography (GC). Specific trace impurities determined include non-aromatic hydrocarbons, benzene, toluene and individual C9 and C10 aromatic compounds. C10 or higher non-aromatics, if present, may interfere with the determination of benzene, but it can be determined by UOP Method 543. The lower limit of quantitation for any single component is 1 mg/kg (mass-ppm). Impurities at concentrations above 500 mg/kg should be determined by UOP Method 744.