Analysis of Ethanol in Blood using Master SHS Static Headspace Sampler and Master GC Gas Chromatograph

Importance of the Topic

The determination of blood alcohol content (BAC) is critical for forensic and public safety applications, particularly in impaired driving cases where legal defensibility and rapid throughput are required.

Objectives and Study Overview

This study presents a robust, high-throughput method for quantifying ethanol in whole blood using a static headspace sampler coupled to a dual-column gas chromatograph. Key goals include achieving reliable accuracy, precision, and minimal carryover while processing large sample volumes in forensic laboratories.

Methodology and Instrumentation

Samples of whole blood (100 µL) are mixed with an internal standard solution containing 0.2 % 1-propanol and 0.5 M ammonium sulfate. A ten-fold dilution with water reduces viscosity and ensures uniform vaporization. Static headspace extraction at 70 °C with a 15 min equilibration generates reproducible vapor-phase ethanol sampling. A helium carrier stream delivers analytes to two parallel capillary columns.

• Vial conditions: 20 mL screw-cap vials with PTFE septa, 120-position autosampler.
• Headspace parameters: oven 70 °C, manifold 90 °C, transfer line 90 °C; loop pressure 0.5 bar; equilibration 15 min; injection 1 min.
• GC parameters: isothermal 45 °C for 2 min; split inlet at 150 °C; helium flow 8 mL/min; dual FIDs.
• Calibration: 7-point over 0.005–0.50 % ethanol, linear r² ≥ 0.999.
• Quality control: NIST reference checks, blank verification, control sample every 10 injections.

Used Instrumentation

• Dani Master SHS Static Headspace Sampler with 120-vial handler.
• Dani Master GC Gas Chromatograph with paired DB-Alc1 and DB-Alc2 columns.
• Dual flame ionization detectors (FIDs) and bar-code vial identification.

Main Results and Discussion

Dual-column analysis achieved resolution factors > 1.0 for critical compounds (methanol, acetaldehyde, ethanol, isopropanol, acetone, n-propanol). Ethanol retention times were under 1 min on DB-Alc1 and near 1.0 min on DB-Alc2. The internal standard peak eluted by 1.5 min, limiting cycle time. Reproducibility across triplicate injections per calibration level met forensic accuracy requirements.

Benefits and Practical Applications

• Minimal sample preparation reduces contamination and extends column life.
• High automation and bar-coded sample tracking ensure chain-of-custody integrity.
• Rapid run times (< 90 s) enable throughput of up to 900 samples per day.
• Reliable performance supports legal defensibility in BAC reporting.

Future Trends and Opportunities

Advancements may include alternative internal standards (e.g., t-butanol), faster stationary phases, integration with mass spectrometry for screening additional volatiles, and further miniaturization of headspace modules. Increased automation and data analytics will enhance laboratory workflow and compliance with evolving forensic regulations.

Conclusion

The combination of a Dani Master SHS sampler and Dani Master GC delivers a fast, precise, and legally defensible approach to blood ethanol analysis. This method addresses high-volume forensic demands through robust headspace extraction, dual-column separation, and streamlined calibration protocols.

References

• Christmore DS, Kelly RC, Doshier LA. Journal of Forensic Science. 1984;29(4):1038–1044.
• Kolb B, Ettre LS. Static Headspace-Gas Chromatography: Theory and Practice. 2nd ed. John Wiley & Sons; 2006.