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Caption : fig. s1 a chromatogram of nicotine and n-heptadecane. the signal intensity is amplified 200 times for areas with retention times of 5 to 9 minutes to highlight the peaks of nicotine and n-heptadecane.

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Caption : fig. s2 the photoionization mass spectra of aerosol particles generated by (a) 6% nicotine e-liquid, (b) 4.5% nicotine e-liquid, (c) 3.5% nicotine e-liquid, (d) 2.5% nicotine e-liquid, (e) 1.5% nicotine e-liquid, (f) 0.5% nicotine e-liquid, (g) e-cigarette r, (h) e-cigarette y, (i) e-cigarette v, and (j) e-cigarette k.

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Caption : fig. s3 (a) photoionization mass spectrum of the background of the vuv-ams, (b) photoionization mass spectrum of the e-cigarette aerosols after passing the cambridge filter, (c) photoionization mass spectrum of e-cigarette f aerosol particles.

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Caption : fig. s4 the particle size distribution of aerosols produced by e-liquids with different nicotine concentrations. the horizontal axis is logarithmic, and the vertical axis represents the logarithmic distribution of the mass concentration per unit volume of particles.

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Caption : fig. s5 the particle size distribution of aerosols generated by five different commercial e-cigarettes.