Determination of e-cigarette aerosol pH using ISFET pH ... · ‐Easy, but incorrect, use of CDC...

Determination of e-cigarette aerosol pH using ISFET pH electrode and

nicotine absorption by saliva using a glassmouth and saliva pH change

John H. Lauterbach, Ph.D., DABT

Lauterbach & Associates, LLC

211 Old Club Court, Macon, GA 31210 USA

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Outline for presentation • Introduction • Determining pH in aqueous and nonaqueous systems • Importance of pH-values for e-liquids and aerosols generated

from e-liquids – chemical and toxicological perspectives • Why e-cigarette aerosols are different from mainstream

cigarette aerosols – a big difference some try to ignore • Approaches for determination of e-cigarette aerosol pH-values • Experimental • Results from most recent experimental work • Use of the glassmouth for estimating changes in saliva pH after

exposure to e-cigarette aerosols • Results from experiments with the glassmouth • Conclusions 2016 CORESTA ST46 LAUTERBACH & ASSOCIATES, LLC 2

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Introduction • Numerous reports on determination of pH-values on main-

stream cigarette smoke (MSS) now just tobacco-science history • US FDA draft guidance on PMTA for ENDS recommends pH-tests

‐ “In addition to the constituents, FDA recommends that you report the pH of the e-liquids tested and the resulting aerosol.” (Lines 1060-61)

‐ No methods given for making the pH determinations • Others have also made pH of e-liquids an issue

‐ Stepanov & Fujioka, Tob Control, Epub 2014 May 14 ‐ Lisko et al., Nicotine Tob Res, Epub 2015 Jan 30 ‐ Both articles used US CDC method designed for smokeless tobacco • With e-liquids it results in pH drift and mentholated e-liquids give cloudy mixture • Henderson-Hasselbalch improperly applied to partially nonaqueous system to

estimate percentage unprotonated nicotine (Lisko et al.) • Our objective is to put better science in to e-liquid pH research

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Like pushing a wet rope up hill • Determining pH-values of e-liquids and e-cigarette aerosols is

like pushing a wet rope uphill – everything works against you ‐ Most pH (glass) electrodes designed for aqueous solutions • Need flow of electrolyte from inside electrode across glass membrane • Organic solvents can slow electrode response and yield pH values that are

different than they would be in true aqueous solution • E-liquids are mostly VG and/or PG and glass pH electrodes do not work well • Problems recently summarized by St. Charles et al., 70th TSRC, Paper #77

‐ MSS more like a suspension of insoluble organic matter in an aqueous mixture; this is why glass electrode works for MSS pH determinations • Technique developed by Sensabaugh and Cundiff, Tob. Sci., 1967 • Health-Canada Method T-113

• Nonstandard pH electrodes work better for e-liquids and aerosols – designed for low-water situations such as bread dough, denim fabric, emulsions, fats, and leather


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Why are pH-values of e-liquids important? • Regulators have said they are important • Chemical importance of pH

‐ Use of pH to control product stability • Minimize microbial spoilage • Flavorful aldehydes can form acetals with PG and VG at less than neutral pH • Acetal formation would decrease flavor amplitude

‐ Potential reactions between e‐liquids and materials in contact with e‐liquids and/or aerosols at other than neutral pH

• Toxicological importance of pH ‐ Potential adverse health effects from mechanical transfer of e‐liquids to

users or others who may come into contact with e-liquids • Spills during filling of devices • Bubbling of e‐liquids from cartomizers

‐ Potential adverse health effects from inhaled aerosols with high pH (Stepanov & Fujioka, 2014)


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One more time: e-cigarette aerosols ≠ MSS • pH-values of e-liquids and e-cigarette aerosols are an attractive

target for those wanting to restrict e-vapor use ‐ Easy, but incorrect, analogy to now-debunked claims of ammonia and

“free-base” nicotine in MSS ‐ Easy, but incorrect, use of CDC method to measure e-liquid pH and

assume aerosol pH is analogous to e-liquid pH • Most e-liquids are solutions, liquid phase of e-cigarette aerosol

likely a solution, gas-vapor phase likely same as ambient air • MSS TPM is mixture of water and water-insoluble materials, gas-

vapor phase is air, water-vapor, CO2, and many other species • Clearly there is a big difference, but we need to be prepared for

the eventuality that others may put good politics ahead of good science


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Approaches for the determination aerosol pH • A pH meter with a flat-bottom electrode (on sale on Amazon)

got the work started • Yes, we could have gotten a pH meter with conventional glass

electrode, but something different was intriguing • After having pH-values of e-cigarette aerosols determined with

by Health-Canada Method T-113 using conventional glass electrode (67 TSRC 78), it was time to do it in-house

• Since 2013, we looked at several approaches for e-cigarette pH ‐ Use of Health-Canada T-113 smoke traps (two configurations) ‐ Several electrode and pH-meter combinations ‐ Use of glassmouth in addition to T-113 trap

• pH-values may not be reflective of human uptake so we are evaluating saliva pH change as a better measure of aerosol pH


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Experimental – 1 • L&ALLC Model IIIb μ‐processor-controlled, constant‐vacuum,

square‐wave e-cigarette puffing system • Puffing regimen of 55/3/30

‐ Flow control by Swagelok SS‐4MG‐SL 10‐turn metering valve acting as critical flow orifice

‐ Flow checked with Sigma‐Aldrich 20414 500-mL bubble meter with Cerulean SC#59138 Restrictor 10CSM (calibrated)(1 kPa)

• pH-Instrumentation – Hach H260G meter with HI 1413B (flat bottom), HI 1053B (conical), and Hach PHW77‐SS (ISFET) probes

• Smoke traps – HC T‐113 normal flow (bottom aerosol inlet for HI probes),reverse flow (side aerosol inlet for ISFET electrode)

• Saliva exposure conducted in glassmouth (Honeycutt, 1985) with depression (≈ 5 mL) for saliva and top port for pH probe


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Experimental – 2


Smoke trap with good aerosol density

Reverse smoke trap with ISFET electrode

Glassmouth in action with typical cigalike

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Results from most recent experimental work– 1


Effects of adding nicotine to water and water/PG/VG solutions

No added nicotine Nicotine added at ≈ 1%

Ratio Water/PG/VG Run 1 Run 2 Run 3 Run 1 Run 2 Run 3

100/0/0 6.27 6.24 6.18 9.11 9.21 9.21

90/5/5 6.68 6.42 6.43 9.16 9.25 9.17

80/10/10 7.08 6.85 6.81 9.27 9.21 9.18

70/15/15 6.58 6.37 6.34 8.93 8.81 8.86

60/20/20 6.39 6.25 6.31 8.84 8.86 8.84

50/25/25 6.49 6.39 6.46 8.61 8.58 8.58

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5.5

6.0

6.5

7.0

7.5

8.0

8.5

1 32 62 92 122 152 182 212 242 272 302 332 362 392 422 452 482 512 542 572 602 632 662 692 722 752 782 812 842

pH

Time (seconds)

MarkTen Menthol 3.5 and MarkTen Fusion 2.5 HI 1413B Electrode

Menthol 1 Menthol 2 Menthol 3 Fusion 1 Fusion 2 Fusion 3

25 puffs

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25 puffs

5.5

6.0

6.5

7.0

7.5

8.0

8.5

1 31 61 91 121 151 181 211 241 271 301 331 361 391 421 451 481 511 541 571 601 631 661 691 721 751 781 811 841

pH

Time (seconds)

MarkTen Menthol 3.5 and MarkTen Classic 2.4 Hach PHW77‐SS (ISFET) Electrode

Classic 1 Classic 2 Classic 3 Menthol 1 Menthol 2 Menthol 3

25 puffs

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Use of glassmouth to estimate change in saliva pH • Depending on the e-liquid, the device, and user behavior there

can be noticeable buccal retention of the e-cigarette aerosol • Presumable the pH of the aerosol may play a part in how much

of the aerosol in retained by the saliva in the mouth • One way of estimating this retention is to determine the pH

change in saliva before and after exposure to e-cigarette aerosol • In our latest experiments we exposed two different types of

artificial saliva (5 mL) to 50 puffs (55/3/30) of e-cigarette aerosol ‐ Pickering Laboratories 1700-0304, pH ≈6.8 (pharmaceutical research) ‐ Pickering Laboratories 1700-0301, pH ≈4.9 (Fusayama/Meyer) ‐ Saliva pH measured before and after exposure ‐ Puff-by-puff pH measured during the run using HI 1053B electrode ‐ V2 Menthol 2.4, Mark Ten Menthol 3.5 and Classic 2.4 used for studies


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Results from experiments with the glassmouth – 1 • Change in pH after exposure to 50 puffs – pH 4.9 saliva

‐ V2 2.4 Menthol: +0.68 (not inserted to ring), 1.06, 0.94 ‐ MarkTen 3.5 Menthol: +0.67, 0.81 (cartomizer weight loss: 0.24, 0.25) ‐ MarkTen 2.4 Classic: 0.56, 0.77 (cartomizer weight loss 0.23, 0.21)


5.5

6

6.5

7

7.5

8

1 61 121 181 241 301 361 421 481 541 601 661 721 781 841 901 961 1021 1081 1141 1201 1261 1321 1381 1441

pH

Time (seconds)e

Glassmouth Runs 1 – 3, V2 Menthol 2.4, pH saliva 4.9

RUN 3 RUN 2 RUN 1

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Results from experiments with the glassmouth – 2 • Saliva nicotine determination by HPLC

‐ Simple procedure: 25 µL injection of micro-filtered saliva ‐ Waters µ-Bondapak C18, 30 cm x 4.6 mm, 2.2 mL/min flow 65/35

MeOH/water, UV detection @254 nm with Waters 486 TAD

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15 V2 Menthol 2.4 MarkTen Menthol 3.5 MarkTen Classic 2.4

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Conclusions • We have developed a simple, robust, and low-cost techniques

for estimating the pH-values of e-liquids ‐ Avoids problems of direct pH-determinations on e-liquids ‐ Simple puffing engine for creating the aerosols ‐ Eliminates problems with use of standard glass pH electrode and overly-

high pH-values • We have developed a multifunctional technique that not only

permits estimating the pH-values of the aerosol generated from an e-liquid and, ‐ Use of a glassmouth to permit exposure of saliva to e-cig aerosol ‐ The change in saliva pH resulting from contact with the e-cig aerosol ‐ The amount of nicotine the saliva absorbs from the e-cig aerosol


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Acknowledgement Much of the laboratory work just presented including all of the instrument interfacing, µ-processor programming, and data reduction was done by Sebastian J. Lauterbach, a contractor to Lauterbach & Associates, LLC.


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Determination of e-cigarette aerosol pH using ISFET pH ... · ‐Easy, but incorrect, use of CDC...

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Transcript of Determination of e-cigarette aerosol pH using ISFET pH ... · ‐Easy, but incorrect, use of CDC...