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

1Tobacco Science Research Conference, Naples, FL, Sept. 20-23, 2015

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Introduction

2Tobacco Science Research Conference, Naples, FL, Sept. 20-23, 2015

• 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

Questions ?21Tobacco Science Research Conference, Naples, FL, Sept. 20-23, 2015

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