Abstract: The objective of the study was to establish a method to determine the gas/particle nicotine in mainstream cigarette smoke with denuder technology. The mainstream smoke from a lit cigarette was passed through a coated denuder in laminar flow by a pump and the remaining smoke was collected by a Cambridge filter pad attached to the exit of the denuder. The interior of the denuder and the filter were extracted by dichloromethane before internal standards were added. The extracts were analyzed by gas chromatography-mass spectrometry. The results show that the gas phase nicotine proportion (f_gas) increased with the exit smoke temperature (ranging from 293 K to 323 K). The determined fraction (f_gas) was ca. 0.094 8% at 308 K. The method can be used to understand potential effects of gas/particle nicotine partitioning from cigarette designs, next generation nicotine and tobacco products such as electronic cigarettes and tobacco heating products.