In this MSTips, we report the measurement result of Polyphenylene Sulfide (PPS), an engineering plastic with excellent heat and chemical resistance. It is known that differences in the manufacturing process of PPS appear in the end groups, so structure analysis of the end groups is important. However, PPS is difficult to measure by LC-MS because it is insoluble in common solvents. Therefore, the end groups were estimated using FD, which can measure PPS oligomers even when they are dispersed in a solvent.