volatility characteristics of electronic cigarette aerosols

Volatility Characteristics of

Electronic Cigarette Aerosols

Jacob Swanson1,2, Noah Bock1,2, Will Northrop1

1Dept. of Mechanical Engineering

University of Minnesota – Twin Cities

2Dept. of Integrated Engineering

Minnesota State University – Mankato

2015 Cambridge Particle Meeting

E-Cigarettes (“E-Cigs”) produce an inhalable

aerosol by vaporizing a mixture of liquids

• Nearly all E-cigs use battery to power a heating coil in

contact with a wicking material saturated with E-liquid

• Some are disposable.

2015 Cambridge Particle Meeting 2

Four standard “E-liquid” constituents

• Glycerol, C3H8O3

– Produces aerosol that resembles smoke

• Propylene Glycol, C3H8O2

– Nicotine carrier, reduces viscosity

• Nicotine (0 – 24 mg·mL-1)

– Generally pharma grade

• Flavoring

– FDA approved PG-based food flavoring

Glycerol

Propylene glycol

Nicotine


E-cigs are emerging as a safe

alternative to tobacco cigarettes

• Manufacturers claim E-cigs to be safe

(no “toxic chemicals”)

• User perception of safety: 50% say

“safer” vs 2% say “less safe” in the UK

(http://www.ash.org.uk/)

• 2.5 million E-cig users compared to 45

million smokers in the U.S. (3 mil+ in

the UK)

• 13% of high school students use E-cigs


http://www.ash.org.uk/

5

May, 2015 - http://www.independent.co.uk/


Experimental objectives

• Construct apparatus that allows

continuous, automated use of a typical

E-cig

• Characterize size, concentration, and

composition particles in E-cig aerosol

• Explore the impact of E-liquid

additives and power on E-cig aerosol

• Determine temporal variability of

aerosol properties


Battery powered E-cig apparatus

Air in

Aerosol out

Solenoid

Kanthal (FeCrAl)

heating coil

Cotton wick

Battery

enclosure

20 mm


Battery powered E-cig apparatus

Air in

Aerosol out

Solenoid

Kanthal (FeCrAl)

Heating Coil

Cotton Wick

Battery

Enclosure

20 mm


Primary limitations: battery life and

E-liquid consumption (~ 10 puffs)

E-Smoking Cycle Simulator (E-SCSTM)

+ -4 V

DC Power Supply

Air in

Aerosol out

5 V input signal

Syringe pump


Experimental apparatus and instruments

HEPA MFC

DAQ

E-cig

LII

CS

Vent

DilutionCPC

EEPSThe MFC controller pulses

in synchronization with the

E-cig to simulate a user

taking a puff

20 L/min, 0.1 Hz, 3 s pulse

10 L/min


1500:1

Flavoring and nicotine content have

little impact E-particleTM emissions

1.E+07

1.E+08

1.E+09

1.E+10

5 50 500

dN

/dlo

gD

p,

part

/cm

3

Dp, nm

PG/VG Mix

Flavored No Nicotine

Flavored With Nicotine

Concentrations ~ 1 x 109 particles/cm3 ~ same as tobacco smoke


The following slides all show

“solid particles” measured

downstream of a catalytic stripper


1. Averages of 10 puffs

2. Extended evaluation of the life of

the coil

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

100 102 104 106 108 110

Co

nc

en

tra

tio

n, p

art

/cm

3

Puffs

Puff sequence shows highly repeatable

solid E-particle emissions


Increasing power increases solid particle

emissions; flavoring has little effect

0.E+00

2.E+06

4.E+06

6.E+06

8.E+06

1.E+07

1 10 100

dN

/dlo

gD

p, p

art

/cm

3

Dp (nm)

PG/VG 18 W

PG/VG 13 W


1 10 100

Dp (nm)

Flavor No Nicotine 13 W

Flavor With Nicotine 13 W

PG/VG 13 W

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

0 100 200 300 400

Co

nc

en

tra

tio

n, p

art

/cm

3

Puffs

Small variation likely due to inconsistent wick saturation

400 puffs shows solid particle emissions

are relatively stable over coil life


0.E+00

1.E+06

2.E+06

3.E+06

0 200 400 600

Co

nc

en

tra

tio

n, p

art

/cm

3

Puffs

0 200 400 600

Puffs

Flavored E-liquids with and without nicotine

show similar results to standard PG / VG


Flavor, no nicotine Flavor, with nicotine

LII does not respond to solid E-particles,

suggesting they are not primarily carbon

0

5

10

15

20

25

0 100 200 300

Mass c

on

cen

tra

tio

n,

µg

/m3

Puffs

EEPS LII


Solid E-particles were collected on silver

membrane filters for Laser Induced

Breakdown Spectroscopy (LIBS) analysis

• ~ 3 µg/m3 for 3 seconds @ 2.6 L/min = 0.39 ng/puff

• 350 puffs

• ~ 1 µg of solid particles per cm2 of filter

CSHEPA MFC

DAQ

E-cig

Filter Area = 0.128 cm2


LIBS results not conclusive – only

calcium identified above LOD


0

1000

2000

3000

Ag 328 Ag 338 Ca Cr Rb

Inte

ns

ity (

a.u

.)

Flavored with nicotine Unloaded filter

We thank TSI for loan of the LIBS for this work

Summary

• Semi-volatile E-particles (~ 60 nm in size) are emitted in extremely high concentrations

• 10 nm solid particles are emitted in lower concentrations (1 x 106 part/cm3) and their composition is unknown

• Time (# puffs), E-liquid, flavoring, nicotine all had relatively little impact of solid and semi-volatile E-particle emissions

• Future work includes better LIBS analysis and FTIR detection of gases of interest (HCHO, N2O)


volatility characteristics of electronic cigarette aerosols

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