This method is for determining the isomer distribution in C15 through C20 mono-substituted linear alkylbenzenes (LABs). The 6-phenyltridecane and 7-phenyltridecane isomers are not resolved from each other and are determined as a composite. The lower limit of detection for a single component is 0.1 mass-%.

Components other than linear alkylbenzenes are not normally determined by this method, however, an estimate of the total LAB content of the sample may be obtained by measuring the components present in the sample other than the LABs. A calculation is included to determine the number average molecular weight of the LABs in the sample, if needed.