This method is for determining trace paraffins and naphthenes by carbon number from C3 through C10 in olefin-free C6, C7 or C8 aromatics or mixtures thereof (see Note 1). The range of detection for C3 to C8 paraffins or naphthenes is 2 to 2,000 mass-ppm. The range of detection for C9 and C10 paraffins and naphthenes is 100 to 2,000 mass-ppm.