Determination of Critical Micelle Concentration of Surfactants by Headspace Gas Chromatography

This paper presents a new method for the determination of the critical micelle concentration (CMC) of surfactants in water at elevated temperatures using headspace gas chromatography (HS‐GC). A volatile compound (e.g., toluene) was spiked into the studied solution. At a given temperature, the concentration of volatile species in the vapor phase (measured by HS‐GC) is proportional to the surfactant concentration in the liquid phase in a closed vial. This tendency will change after the solution is saturated with surfactant. By plotting the GC signal of the vapor species vs the concentration of the surfactant concentration in the solution, a breakpoint, i.e., corresponding to the CMC of the surfactant. The present method has good precision (RSD < 10%) and good accuracy. It is also very simple and can be used as an automated method for determining the critical micelle concentration of surfactants at the temperature of interest.