Real-time characterization and quantification of aerosol components for open- and Closed-Ended heated tobacco products

[Display omitted] •Aerosol particle phase compositions in HTPs were quantified online for the first time.•Short-lived intermediates during ring opening reactions were observed in gas phase.•Time-mass profile of nicotine release was given within a puff.•Chemical delivery quantity decreased with prolonged puff durations in Close-ended HTPs. To characterize fast and dynamic thermophysical processes of aerosol formation from heated tobacco products (HTPs), a real-time chemical detection and quantification at sub-second time resolution is of great significance. Herein a novel vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometer (PI-TOFMS) was adapted for on-line chemical analysis of gaseous and particulate aerosol fractions formed from two HTP systems of contrasting designs. The two HTP systems used a battery-powered heating mechanism to heat tobacco rods containing granulated tobacco materials, one puffing air to flow through the tobacco bed and the other with no puffing air going through the tobacco section (termed as open-ended and close-ended, respectively). The on-line PIMS analyzer was able to detect a great number of mass peaks, including nicotine (Nic), glycerin (VG) and propylene glycol (PG) etc in the particulate phase, and flavor components such as 2,3-Butanedione and triethyl citrate in both gaseous and particulate phases. In particular, some short-lived intermediates such as ethenol and propen-2-ol from pyrolysis of the tobacco granules were observed and identified on-line. Nic, VG and PG were quantified with a high time resolution of 0.5 s using their standard calibration curves established with PI-TOFMS. The time-resolved evolving mass profiles of Nic, VG and PG were obtained in near real-time, as well as Nic release rate within a single puff for the first time. In addition, the present results clearly revealed that the change in puffing air flow pathway along the tobacco rod from the open-ended to the close-ended configurations significantly altered the Nic delivery pattern, in which a stable Nic delivery profile in the open-ended HTP at prolonged puff durations was reduced in the close-ended HTP. These findings can be utilized to develop suitable HTPs that could mimic the Nic delivery and hence help smokers to quit smoking.