This method is for determining trace impurities in high-purity mixed xylenes by gas chromatography. 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 determina-tion of benzene, but it can be determined by UOP Method 543. The range of detection for any single com-ponent is 5 to 500 mass-ppm. Impurities at concentrations above 500 mass-ppm should be determined by UOP Method 744.