Blood Alcohol Analysis on Rtx®-BAC Plus 2

Significance of Topic

Blood alcohol quantification is vital for forensic toxicology, clinical diagnostics and regulatory compliance. Rapid, accurate separation of ethanol from endogenous and exogenous volatiles ensures reliable results in high-throughput laboratories.

Objectives and Study Overview

This study demonstrates a sub-3-minute headspace GC-FID method using the Rtx®-BAC Plus 2 column for simultaneous resolution of ethanol and six related volatile compounds. The aim is to maximize throughput without compromising chromatographic resolution.

Methodology and Instrumentation

Sample Preparation

• 50 µL of each control standard (acetaldehyde, methanol, ethanol, acetone, isopropanol at 100 µg/mL; tert-butanol, n-propanol at 50 µg/mL) diluted in 900 µL water in 20 mL headspace vials
• Equilibration at 60 °C for 5 min, vial pressurized to 30 psi for 1 min

Headspace Injection

• Tekmar HT3, loop-split injection (50:1), loop pressure 20 psi, fill time 1 min, injection time 3 min
• Inlet temperature 200 °C, transfer line 125 °C

GC-FID Conditions

• Agilent/HP 6890 with FID at 240 °C
• Rtx®-BAC Plus 2 column (30 m × 0.32 mm ID, 0.6 µm film)
• Oven: initial 40 °C hold 3 min; valve oven 125 °C
• Carrier gas He at constant flow, linear velocity 80 cm/s
• Make-up gas N₂ at 30 mL/min

Main Results and Discussion

Baseline separation of seven analytes is achieved in under 3 min. Retention times range from 0.81 min for acetaldehyde to 1.66 min for n-propanol. Ethanol elutes at ~1.03 min, fully resolved from methanol and acetone peaks, ensuring accurate quantitation even at low concentrations.

Benefits and Practical Applications

– High throughput: sub-3-minute cycle time accelerates sample throughput in busy forensic and clinical labs
– Robust resolution: clear separation of ethanol from interfering volatiles enhances data quality
– Simplicity: straightforward headspace sample prep reduces manual steps and potential errors
– Versatility: applicable to blood, breath and beverage alcohol testing, as well as screening in pharmaceutical and environmental settings

Used Instrumentation

– Headspace sampler: Tekmar HT3
– Gas chromatograph: Agilent/HP 6890 GC with FID detector
– Column: Rtx®-BAC Plus 2, 30 m × 0.32 mm ID, 0.6 µm film

Future Trends and Potential Applications

Emerging developments include integration of GC-MS for confirmatory analysis, micro-headspace technologies for reduced sample volumes, automated data processing with AI-driven algorithms and portable GC systems for on-site testing and law enforcement use.

Conclusion

The Rtx®-BAC Plus 2 column combined with optimized headspace GC-FID parameters provides rapid, reliable separation of ethanol and key volatiles in under 3 minutes, improving laboratory efficiency and analytical confidence in blood alcohol analysis.