Development of a highly sensitive analytical technique for surfactants by time-of-flight secondary ion mass spectrometry

We have developed a highly sensitive analytical technique for detecting the distribution of surfactants existing on a polymer surface. We studied the chemical modification of surfactants with the hydroxyl group by using amine-containing compounds in the gaseous phase at 23 °C; then, we performed measurements by using time-of-flight secondary ion mass spectrometry (TOF-SIMS). We found that 4-(dimethylamino) phenyl isocyanate as a modification reagent is capable of modifying the hydroxyl group when 1,8-diazabicyclo5,4,0]undec-7-ene (DBU) is used as a catalytic agent. We demonstrated this modification with stearyl alcohol on a polymer material surface. The signal sensitivity of stearyl alcohol after the modification increased considerably in comparison with that of the unmodified stearyl alcohol. Moreover, we confirmed that this modification method can be used for the distribution analysis of surfactants. The distribution conditions of traces of surfactants with the hydroxyl group can be observed clearly by using this modification method.