A method includes determining a critical micelle concentration (Ccm assumed) of a sample with an unknown concentration (Cs) of a surfactant based on an assumed surfactant concentration (Cassumed) of the sample, providing a benchmark solution with a known concentration of the surfactant, determining an actual critical micelle concentration (Ccm) of the surfactant from the benchmark solution, and calculating the unknown concentration (Cs) of the surfactant in the sample from the following equation: Cs=Ccm/(Ccm assumed/Cassumed).