The Heat of Vaporization of Nicotine
from Tobacco
Kelley St.Charles 1, Serban Moldoveanu 2
1) Consultant to R.J. Reynolds Tobacco Company 2) R.J. Reynolds Tobacco Company, Winston-Salem, NC
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Introduction
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• Follow up to 2014 TSRC Paper*• Nicotine vapor pressure at 23 ºC measured• Pure nicotine and multiple tobacco types• Vapor pressure since measured at higher
temperatures
*K. St.Charles & S. Moldoveanu, Nicotine activity in tobacco. Paper # 40.
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Introduction
Clausius-Clapeyron Equationln(P) = - ΔHvap /RT + C
P = Vapor Pressure (any pressure units)ΔHvap = Heat of vaporization* (J/mol)R = Gas Constant (8.314 J/K/mol)T = Absolute Temperature (K)C = Unitless constant
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* Enthalpy of Vaporization or Sublimation
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Experimental
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Rearranged Clausius-Clapeyron Eqn.
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ln(P) = (-ΔHvap/R) * 1/T + C
• Vapor P measured at 23, 30, 40 ºC• Linear regression of ln(P) versus 1/T• Slope = -ΔHvap/R• ΔHvap = - Slope * R
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Experimental summary
• Details in 2014 presentation• Used pure nicotine and multiple tobacco types• Samples stored in Al-foil lined gas bags with septum• Diaphragm pump to sample 2 L headspace (HS) from
tobacco• 10 mL gas-tight syringe to sample pure nicotine HS• HS sampled through XAD-4 cartridge similar to ETS
nicotine• Pure nicotine HS also sampled directly in syringe
containing extraction solution
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Experimental summary (cont.)
• Analysis by GC/MS/MS– Ethyl acetate solvent with 5000 ppm triethylamine– Deuterated nicotine (methyl -d3) internal standard– MRM Nicotine m/z 162 → 84 & m/z +3 for internal standard– 30 minute run time
• Calibration from 4.2 – 2140 ng/mL nicotine
• Signal to noise = 240 @ 8.3 ng/mL
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Foil-lined gas bag modified• 1/8” stainless steel Swagelok® union replaced
Restek® polypropylene septum holder– Bulkhead union nut inside bag– PTFE lined septum replaced back ferrule outside bag
• Outer changed to Sorbent Systems bag– 5 mil (127 µm) thick, 4-layer film: PET/PE/Al foil/PE– ~20 x 25 cm (nicotine HS) & 40 x 50 cm (tobacco HS)
• Heavy-duty Al foil (~23.5 µm) inner liner– Added Al tape to reinforce foil at union penetration– Edges double folded and reinforced with Al tape– Tested heavier gauge foil with pure nicotine
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Tobacco headspace sampling
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Needle
XAD-4Cartridge
½ of size 6D Silicone Stopper
4.8 ID x 7.9 OD mm Tubing
4.8 x 7.9 mm Tubing
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Tobacco types
Conditioned to water activity = 0.61Used 50+ g per bagBags filled with nitrogen
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Results
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Pure nicotine vapor pressure
XAD-4 = 62% of in-syringe sampling
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Pure nicotine resultsIn-syringe comparison to published results
A. Harlan & Hixon. Ind Eng Chem. 1928, 20(7): 723–724.
B. Walker et al. Chem Senses. 1990, 15(2): 165-177
C. Norton et al. J Amer Chem Soc. 1940, 62: 261-264.
D. Boldridge & Kelly. 1988. Eqn. 6. http://legacy.library.ucsf.edu/tid/usx83d00/pdf
E. Johnson. 1990, Eqn. 2. http://legacy.library.ucsf.edu/tid/fma51f00/pdf
F. Banyasz. 1999. Eqn. 2. in: Analytical determination of nicotine and related compounds and their metabolites. p.153
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Linear Regression ofln P vs 1/TR2 = 0.9995
ΔHvap = 56.6 kJ/mol
Ref A = 64.4 kJ/molRef D = 72.3 kJ/molRef E = 82.4 kJ/molRef F = 65.0 kJ/mol
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Nicotine vapor from tobacco
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*Activity = Vapor Pressure / Pure Nicotine Vapor Pressure
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Nicotine vapor pressure
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• Pure nicotine vapor pressure – 110 – 240 X > Burley
– 700 – 1100 X > Flue Cured
– 3200 – 7600 X > Oriental
• Vapor P Burley 6–10 X > Flue Cured 4-5 X > Oriental• Vapor P Cigarette blends ≥ Flue Cured• Tobacco nicotine activity slightly with temperature
(i.e. relative vapor pressure increases more than pure nicotine)
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Nicotine activity in tobaccoUn-protonated calculated using:1. Tobacco % nicotine (DWB)2. Tobacco extract pH3. pKa as f(temperature)*
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*Clayton et al. 2013, Anal. Methods, 81-88
Polynomial RegressionY = 14.12 X – 5542 X2
Intercept term not significant
R2 = 0.986Std. Error = 0.04% Activity
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Heat of vaporization - ΔHvap
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No obvious trends with respect to:– Tobacco origin, type, stalk position, or nicotine concentration– Wide range of nicotine activities
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Combined heat of vaporization
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• Mean ΔHvap = 86.7 kJ/mol, SD = 5.6 kJ/mol• 30 kJ/mol more endothermic than pure nicotine
– ΔH for mono-protonated → un-protonated nicotine reported as 34A & 41B kJ/mol*
– Property of nicotine rather than tobacco type
• Supports 2-step vaporization process from tobacco1. Dissociation of mono-protonated to un-protonated nicotine
2. Vaporization of un-protonated nicotine
A. Banyasz.1999 in: Analytical determination of nicotine and related compounds and their metabolites. p.159
B. Clayton et al. 2013, Anal. Methods, 81-88
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Conclusions• Pure nicotine vapor P & ΔHvap similar to literature
(foil lined gas bags + in-syringe extraction)
• Pure nicotine vapor P 110 – 7600 X greater than that from tobacco
• Nicotine activity of Burley > Flue Cured > Oriental• Activity appears a function of un-protonated nicotine
concentration and temperature• Tobacco moisture can also influence nicotine activity
(Observed but not quantified).
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Conclusions – ΔHvap from tobacco
• ΔHvap did not depend on tobacco origin, type, stalk position, nicotine concentration or activity
• ΔHvap depends on the nicotine properties rather than tobacco properties
• Mean ΔHvap = 86.7 kJ/mol, RSD = 6.5%• Supports 2-step vaporization process from tobacco
1. Dissociation of mono-protonated to un-protonated nicotine (~30 kJ/mol)
2. Vaporization of un-protonated nicotine (~57 kJ/mol)
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Thanks to
• R.J. Reynolds Tobacco Company Research and Development
• You for listening
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