Analysis of Eight Carbonyl Compounds in E-Cigarette Liquid using High-Performance Liquid Chromatography

Importance of the Topic

E-cigarettes are widely used as alternatives to traditional cigarettes, but their heating process generates harmful carbonyl compounds. Monitoring these compounds in e-liquids is essential for assessing health risks and ensuring product safety.

Objectives and Study Overview

This study presents a high-performance liquid chromatography method to simultaneously quantify eight carbonyl compounds derivatized with DNPH in e-cigarette liquids. The method aims to meet the China Electronics Chamber of Commerce standards limiting carbonyls to 20 mg/kg (180 mg/kg for acetaldehyde).

Methodology and Instrumentation

• Instrumentation Used
  
  • Shimadzu LC-2050C 3D HPLC system with UV detection at 365 nm
  • Shim-pack GIST C18-HP column (150 mm × 4.6 mm, 5 µm)
  • Gradient elution with three mobile phases:
    • Phase A: Water/acetonitrile/THF/isopropanol (63:27:9:1)
    • Phase B: Water/acetonitrile/THF/isopropanol (40:58:1:1)
    • Phase C: Acetonitrile
  • Flow rate: 1.25 mL/min; Column temperature: 50 °C
• Sample Preparation
  
  • Derivatization reagent: DNPH in acetonitrile with phosphoric acid, stored in amber bottle
  • Standard solutions: DNPH derivatives at 0.05–5.0 mg/L for calibration
  • Sample: 0.1 g e-liquid mixed with derivatization reagent, reacted 20 minutes, diluted, filtered

Results and Discussion

• Separation and Chromatography: Baseline resolution achieved for all eight DNPH derivatives, with critical resolution of 1.636 between acetone and acrolein peaks.
• Sensitivity: Limits of detection ranged from 0.008 to 0.063 mg/kg and quantitation limits from 0.027 to 0.210 mg/kg, exceeding required sensitivity (0.5 mg/kg).
• Linearity: Calibration curves displayed excellent linearity (R2 > 0.9996) over 0.05–5.0 mg/L.
• Recovery: Spike recoveries between 87.4% and 99.9% at 20 mg/kg level.
• Precision: Retention time RSDs ≤ 0.22% and area RSDs ≤ 4.29% across concentrations (0.1, 0.5, 2.0 mg/L).
• Sample Analysis: Six commercial e-liquids tested; several exceeded formaldehyde, acetone, and acrolein limits, indicating variable product safety.

Benefits and Practical Applications

• Provides a validated, sensitive, and robust protocol for routine quality control of e-cigarette liquids.
• Enables regulatory compliance by accurately quantifying multiple carbonyl compounds.
• Offers a rapid approach for risk assessment in the tobacco and inhalation product industry.

Future Trends and Applications

• Integration with automated sample preparation and ultra-high-performance systems to increase throughput.
• Expansion to additional analytes such as volatile organic compounds or flavoring agents.
• Application of mass spectrometry detection to improve specificity and quantitation.
• Development of portable HPLC or sensor-based methods for on-site monitoring.

Conclusion

The presented HPLC method delivers high sensitivity, precision, and accuracy for eight carbonyl compounds in e-cigarette liquids. It fulfills regulatory requirements and serves as a reliable tool for safety assessment and quality control in e-cigarette research and industry.

Reference

No specific literature references were listed in the original text.