Measurement of Ethanol in Blood Using Headspace GC-MS

Significance of the Topic

Ethanol blood concentration plays a critical role in forensic investigations of traffic incidents, violent crimes, and clinical toxicology. Precise quantification of blood ethanol supports legal determinations of impairment and informs public safety measures.

Objectives and Study Overview

This study assessed the suitability of headspace GC-MS for measuring ethanol in blood across concentrations relevant to regulatory limits. Key goals included developing a robust calibration range, confirming chromatographic separation from sampling contaminants, and evaluating method precision at threshold levels.

Methodology and Instrumentation

• Sample Preparation: Aqueous ethanol standards (0.03 to 2.0 mg/mL) were prepared in ultrapure water. Blood from non-drinking volunteers was spiked with ethanol at 0.3 mg/mL. A 1-propanol solution (0.5 mg/mL) served as the internal standard.
• Headspace Treatment: Samples (0.5 mL) and internal standard solution (0.5 mL) were sealed in 22 mL headspace vials with PTFE/butyl septa. Thermal equilibration and vapor sampling were conducted under constant headspace mode.
• Instrument Conditions:
  • Headspace Sampler: TurboMatrix HS; vaporization chamber at 200 °C; injection time 0.05 min.
  • Gas Chromatograph–Mass Spectrometer: Shimadzu GCMS-QP2010 Ultra with Rtx-BAC2 capillary column (30 m × 0.32 mm, 1.2 μm). Oven program: 40 °C (5 min), ramp to 200 °C at 40 °C/min (1 min hold). Helium carrier gas.
  • Mass Spectrometer: Electron ionization; interface at 230 °C; ion source at 200 °C; scan range m/z 29–300.

Main Results and Discussion

The method achieved complete chromatographic separation of ethanol, 1-propanol, and 2-propanol, eliminating interference from antiseptic residues. The calibration curve over 0.03 to 2.0 mg/mL displayed excellent linearity (R² = 0.99996). Repeatability tests yielded %RSD of 1.56% for 0.03 mg/mL aqueous standards and 1.70% for 0.3 mg/mL spiked blood, demonstrating high precision at regulatory thresholds.

Benefits and Practical Applications

• Mass spectral confirmation ensures specificity and minimizes false positives.
• Direct headspace coupling reduces sample handling and lowers carrier gas consumption.
• Suitable for forensic casework, traffic law enforcement, workplace screening, and clinical toxicology.

Future Trends and Potential Applications

• Automation and high-throughput integration for forensic and clinical laboratories.
• Development of portable GC-MS systems for on-site alcohol screening.
• Advanced MS techniques to differentiate endogenous versus exogenous ethanol sources.

Conclusion

Headspace GC-MS provides a robust, precise, and specific approach for blood ethanol analysis at concentrations relevant to legal impairment criteria. Its streamlined workflow and efficient gas usage make it an essential tool in forensic and analytical laboratories.

References

• Osamu Suzuki, Mikio Yashiki (eds.): Practical Handbook for the Analysis of Toxic Pharmaceuticals with a Focus on Chromatography, Jiho, Inc., Tokyo 2002.
• The Pharmaceutical Society of Japan (eds.): Testing Methods and Annotation for Toxic Pharmaceuticals 2006 – Analysis, Toxicity, and Coping Methods, Tokyo Kagaku Dojin, Tokyo 2006.