LABSTAT INTERNATIONAL ULC.262 Manitou Drive
Kitchener, Ontario, Canada N2C 1L3Phone: (519) 748-5409 Fax: (519) 748-1654 Web: www.labstat.com
Angel Rodriguez-Lafuente, Romulo Lodevico, Mehran Sharifi, Peter Joza, W.S. (Bill) Rickert
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71th Tobacco Science Research ConferenceNovember 30, 2017
Bonita-Springs, Florida USA
Analysis of Organic Acid Content in E-liquids and E-cigarette Aerosols by HPLC-UV 20
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Organic Acids on E-cigs
➢ Weak organic acids on e-liquid formulations
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Need for analytical solutions!
➢ Impact the aroma and taste of the aerosols
➢ Affect the stability of e-liquids
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Objective
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➢ To develop simple analytical method(s) for the analysis of 6 organic acids possibly found in aerosols and e-liquids.
• Benzoic acid
• Formic, acetic, glycolic, lactic and oxalic acid.
Matrix: Polypropylene Glycol and Glycerol
Sample preparation techniques
Sample analysis (chromatography)
Photo credit: http://vaping360.com
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Sample Generation & Sample Preparation - Aerosols
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➢ E-aerosol: Puffing on linear machine
➢ Aerosol collected onto a filter pad
➢ Pad extracted with 20 mL Isopropanol
➢ (Extract diluted with 0.1% H3PO4)
➢ Analysis by HPLC-UV
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Sample Preparation: E-liquids
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➢ Weight 0.5 mL of e-liquid. Reporting units [/g]
➢ Dilution with 2 mL of 0.1% H3PO4 (1:5 dilution ratio)
➢ Analysis by HPLC-UV
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Method 1 – Determination of Benzoic Acid in E-cigarette Aerosol / E-liquid by HPLC-UV
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Sample AnalysisInstrument: HPLC-UV
Detector λ: 230 nm
Column: Poroshell 120 EC-C18 (2.7 µm,100 X 4.6 mm)
Flow rate: 1.5 mL/min
Mobile Phase: A: 0.1% H3PO4
B: 60% Methanol and 40% Acetonitrile
Time (min) Solvent A (%) Solvent B (%)0.0 95 5
2.0 95 5
2.1 75 25
15.0 75 25
15.1 10 90
18.0 10 90
18.1 95 5
31.0 95 5
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Selectivity
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E-cigarette Aerosol sample
Fortified sample
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Method Characteristics
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Calibration range: 0.19 – 50 µg/mL
R2: 0.9997 (residuals < 5%)
Units LOD LOQ
E-cigarette aerosol [µg/collection] 5.16 17.2
E-liquid [µg/g] 0.516 1.72
LLFM (n=14)
HLFM (n=14) CV
E-cigarette aerosol 108% 108% < 10%
LFM(n=8) CV
E-liquid 102% 5.7%
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Method 2 – Determination of Formic, Acetic, Oxalic, Glycolic and Lactic acid in E-cig
aerosol / E-liquid by HPLC-UV
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Sample AnalysisInstrument: HPLC-UV
Detector λ: 210 nm
Column: Supelcogel C-610H (300 X 7.8 mm)
Flow rate: 0.5 mL/min
Mobile Phase: A: 0.1% H3PO4
B: 100% Acetonitrile
Time (min) Solvent A (%) Solvent B (%)
0.0 100 0
29 100 0
34 90 10
65 90 10
70 100 0
75 100 0
Organic Acids separation
Elution of matrix components
Equilibration
Analyte pKa Retention time (min)
Tailing factor LFM
Oxalic acid 1.2 8.0 1.43
Glycolic acid 3.8 16.2 0.709
Lactic acid 3.9 16.7 1.19
Formic acid 3.8 18.0 0.983
Acetic acid 4.8 20.0 0.992
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Method Characteristics – Linearity & Sensitivity
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AnalyteLinearrange
[µg/mL]
Correlation coefficient
(R2)
Averageresiduals
(%)
E-aerosolLOD
[µg/coll]
E-aerosolLOQ
[µg/coll]
E-liquidLOD
[µg/g]
E-liquidLOQ
[µg/g]
Oxalic acid 0.13 – 34.0 0.99998 < 5% 0.51 1.71 0.12 0.40
Glycolic acid 1.3 – 340 0.99980 < 2% 6.74 22.5 2.17 7.24
Lactic acid 1.3 – 340 0.99974 < 6% 9.21 30.7 2.26 7.53
Formic acid 1.4 - 365 0.99994 < 8% 6.28 20.9 1.34 4.45
Acetic acid 3.2 - 850 0.99997 < 13% 14.2 47.3 3.67 12.7
2 orders of magnitude
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E-cigarette aerosol
Method Characteristics – Accuracy & Precision
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AnalyteLFB
Recovery(%, n=6)
CV(%, n=6)
LFM Recovery(%, n=6)
CV(%, n=6)
Oxalic acid 92.5 4.4 98.9 8.7
Glycolicacid 103 2.3 102 2.5
Lactic acid 103 2.9 99.2 4.1
Formic acid 104 3.6 103 2.2
Acetic acid 106 3.9 107 3.3
AnalyteLFB
Recovery(%, n=5)
CV(%, n=5)
LFM Recovery(%, n=11)
CV(%, n=11)
Oxalic acid 95.8 6.6 105 9.7
Glycolicacid 101 7.6 103 8.1
Lactic acid 101 5.9 100 13
Formic acid 105 12 107 13
Acetic acid 93.7 9.4 108 7.9E-liquid
Accuracy 90 -110%
Precision < 15%
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Practical issues
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Fortified E-Cigarette Aerosol Sample
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Method 3 – Improved Determination of Formic, Acetic, Oxalic, Glycolic and Lactic acid in E-
cigarette aerosol / E-liquid by HPLC-UV
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Sample AnalysisInstrument: HPLC-UV
Detector λ: 210 nm
Column: Allure Organic Acids (5 µm, 300 X 4.6 mm)
Flow rate: 1 mL/min
Mobile Phase: A: 0.1% H3PO4
B: 100% Acetonitrile
Time (min) Solvent A (%) Solvent B (%)0.0 100 0
15 100 0
17 75 25
19 75 25
21 50 50
25 50 50
28 0 0
40 0 0
Mid-calibration standard
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Method Characteristics - Selectivity
17E-liquid fortified with target organic acids
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Method Characteristics – Linearity & Sensitivity
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AnalyteLinearrange
[µg/mL]
Correlation coefficient
(R2)
Averageresiduals
(%)
E-liquidLOD
[µg/g]
E-liquidLOQ
[µg/g]
Oxalic acid 0.15 – 39.0 0.9999 < 11% 0.14 0.47
Glycolic acid 1.04 – 276 1.0000 < 9% 1.12 3.75
Lactic acid 1.04 – 278 1.0000 < 6% 1.49 4.95
Formic acid 1.67 - 445 1.0000 < 5% 1.87 6.24
Acetic acid 2.24 - 596 0.9999 < 11% 1.54 5.10
E-liquidLOQ
[µg/g]
0.40
7.24
7.53
4.45
12.7
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Method Characteristics – Accuracy & Precision
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AnalyteLFB
Recovery(%, n=8)
CV(%, n=8)
LFM Recovery(%, n=8)
CV(%, n=8)
Oxalic acid 85.8 2.7 85.7 4.6
Glycolic acid 100 2.1 106 3.9
Lactic acid 101 2.2 99.7 2.8
Formic acid 97.1 2.4 98.6 6.5
Acetic acid 97.2 3.8 96.0 3.7
E-liquid
Accuracy 85-110%
Precision < 7%
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Conclusions
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➢ Simple extraction/dilution followed by HPLC-UV was developed for the routine analysis of organic acids in E-cigarette aerosols and E-liq matrices
➢ Methods have been fully validated and applied in real samples and stability studies
➢ Chromatography is key for the separation of the organic acids and the main components of the matrix
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Acknowledgements
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Thank you for your attention !
Labstat International ULC Scientists, Sample Preparation Technicians and Analysts.
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