Forensic Analysis of Blood Alcohol Concentration

Importance of Topic

Accurate measurement of blood alcohol concentration is essential in forensic investigations and legal proceedings. Headspace sampling combined with gas chromatography and flame ionization detection provides a reliable approach for quantifying ethanol in biological samples. Advances in instrument configuration can enhance throughput, precision, and robustness for routine laboratory workflows.

Study Objectives and Overview

This application note demonstrates the performance of an Agilent 8860 gas chromatograph equipped with dual flame ionization detectors and an Agilent 7697A headspace sampler for blood alcohol concentration analysis. The study evaluates calibration linearity, repeatability, and compound resolution using single and dual column configurations with J&W DB-BAC1 UI and DB-BAC2 UI capillary columns.

Methodology and Instrumentation

The analytical system comprised the following elements:

• Agilent 8860 GC with split/splitless inlet and dual FIDs
• Agilent 7697A headspace sampler with 1 mL loop and PTFE-lined caps
• J&W DB-BAC1 UI column (30 m×320 µm, 1.8 µm) and DB-BAC2 UI column (30 m×320 µm, 1.2 µm)
• Inert tee for capillary flow splitting to two detectors
• Standard Agilent consumables for vial, ferrules, and liners

Headspace parameters included a 7 min equilibration at 70 °C, 15 psi vial pressure, and 1 min injection time. GC conditions used helium carrier gas, 110 °C inlet temperature, 10:1 split ratio, and a constant oven hold at 40 °C for 4.5 min.

Main Results and Discussion

Calibration over 10–320 mg/dL ethanol with n-propanol internal standard yielded linear responses (R2 > 0.999) for both single- and dual-column configurations. Repeatability studies at 15 and 60 mg/dL showed relative standard deviations below 2 % for peak area and below 0.07 % for retention time. A 12-component BAC checkout mix was fully resolved on each column with symmetric peak shapes, demonstrating reliable separation of ethanol and related volatiles.

Benefits and Practical Applications

The dual-column, dual-FID approach doubles analytical throughput and enhances compound confirmation without sacrificing accuracy or precision. The modular configuration supports routine forensic and clinical BAC testing with minimal method development and robust performance.

Future Trends and Opportunities

• Integration with mass spectrometry for higher specificity and sensitivity
• Increased automation and remote control of headspace sampling processes
• Development of portable headspace-GC systems for on-site screening
• Extension of the method to additional volatile biomarkers and alternative matrices

Conclusion

The Agilent 8860 GC system combined with dual FIDs and the 7697A headspace sampler delivers a cost effective, precise, and high-throughput solution for forensic blood alcohol analysis. Excellent linearity, repeatability, and compound resolution meet stringent method requirements and streamline routine laboratory operations.

References

1. Boswell HA and Dorman FL Uncertainty of Blood Alcohol Concentration Results as Related to Instrumental Conditions: Optimization and Robustness of BAC Analysis Headspace Parameters Chromatography 2015, 2, 691–708