In this work, we present a protocol to characterize the exhaled VOCs in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry (Sec-nanoESI-HRMS). 
Sec-nanoESI-HRMS
The homemade Sec-nanoESI source was readily set up based on a commercial nanoESI source. 
Sec-nanoESI source
The homemade Sec-nanoESI source was readily set up based on a commercial nanoESI source. 
nanoESI source