Guangdong Provincial Engineering Research Center for Online Source Apportionment System of Air Poll 1 article published in JoVE Chemistry Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry Xue Li*1,2, Dan D. Huang*3, Rui Du1,2, Zhi J. Zhang1, Chak K. Chan3, Zheng X. Huang1,2, Zhen Zhou1,2 1Institute of Mass Spectrometer and Atmospheric Environment, Jinan University, 2Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, 3School of Energy and Environment, City University of Hong Kong A protocol for characterizing chemical composition of exhaled breath in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry is demonstrated.