Improved Blood Alcohol Analysis by Resolution of Propanal from Ethanol Using Two Unique GC Column Phases, Zebron™ ZB-BAC1 and ZB-BAC2

Importance of the Topic

Blood alcohol content (BAC) determination by headspace gas chromatography (GC) is a cornerstone of forensic and clinical analysis. Accurate quantification is essential in legal, clinical, and post-mortem contexts. However, endogenous compounds such as n-propanol and propanal can co-elute with ethanol or serve as misleading internal standards, compromising result reliability.

Objectives and Study Overview

This study evaluates two novel GC stationary phases, Zebron ZB-BAC1 and ZB-BAC2, to:

• Resolve propanal from ethanol and other volatile analytes.
• Validate alternative internal standards (t-butanol, 2-butanol) to avoid n-propanol interference.
• Assess method linearity, sensitivity, and reproducibility for routine BAC testing.

Methodology and Instrumentation

Samples of blood alcohol solutions (0.025–0.400% v/v) were prepared in water with internal standards at 0.100% v/v. Analysis was performed on an Agilent HP 6890 GC equipped with an Overbrook Scientific HT-200H headspace autosampler and dual flame ionization detectors. Two capillary columns (Zebron ZB-BAC1 and ZB-BAC2) were connected in parallel. Key parameters included:

• Headspace injection: split 30:1 at 180 °C.
• Carrier gas: helium, constant flow (7.5 mL/min).
• Oven: isothermal at 40 °C (optimized to 30 °C for enhanced propanal resolution).
• Detector: FID at 250 °C.

Key Results and Discussion

The Zebron column pair separated propanal from ethanol and other endogenous compounds under simple isothermal conditions, whereas a conventional Restek BAC column pair failed to resolve propanal on BAC2 and co-eluted t-butanol with acetone on BAC1. Calibration curves for six analytes showed excellent linearity (R² between 0.9961 and 0.9998). Limits of detection ranged from 0.00001% to 0.00006% v/v; limits of quantitation were below 0.0002% v/v, well under forensic requirements. Reproducibility at the lowest calibration point exhibited absolute RSD of 1.1–1.9% and relative RSD of 3.2–4.0% across all internal standards.

Benefits and Practical Applications

Implementing Zebron ZB-BAC1 and ZB-BAC2 columns enables:

• Unambiguous detection of propanal, preventing false elevation of ethanol readings.
• Use of t-butanol or 2-butanol as robust internal standards, avoiding n-propanol variability in post-mortem samples.
• Efficient isothermal analysis without extended run times, supporting high-throughput forensic workflows.

Future Trends and Potential Applications

Advances may include:

• Further miniaturized or ultra-fast GC methods for field-deployable BAC screening.
• Integration with mass spectrometry for enhanced specificity in complex biological matrices.
• Application to other volatile biomarkers in clinical toxicology and environmental monitoring.

Conclusion

The dual-column approach with Zebron ZB-BAC1 and ZB-BAC2 phases offers superior selectivity, sensitivity, and reproducibility for BAC analysis. It resolves propanal interference and expands internal standard options, ensuring more accurate forensic and clinical alcohol determinations.

Reference

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• Countryman S., Kelly K., Fernandez C. Critical Factors in Selecting an Internal Standard for Accurate Determination of Blood Alcohols in Post-Mortem Samples, 2010.