Dual-Column Analysis of Blood Alcohol Content (BAC) with Brevis GC-2050

Importance of the Topic

Blood Alcohol Content (BAC) analysis is critical in forensic toxicology for assessing intoxication and supporting legal investigations. Rapid and accurate quantification of ethanol and other volatile organic compounds (VOCs) in blood improves decision-making in criminal and clinical contexts. Compact, high-throughput instrumentation addresses limited lab space and increasing sample volume.

Objectives and Study Overview

Aim to demonstrate dual-column gas chromatography (GC) using the Brevis GC-2050 with headspace sampler HS-20 NX for BAC analysis. Evaluate chromatographic performance, linearity, repeatability, and separation of ethanol and seven VOCs. Compare calibration in water and blood matrix and explore hydrogen as carrier gas to shorten run time.

Methodology and Instrumentation

Instrument setup:

• Brevis GC-2050 with dual columns (SH-BAC PLUS1 and PLUS2) and Flame Ionization Detectors (FIDs)
• HS-20 NX headspace sampler with twin transfer lines to two FIDs
• Carrier gas: Hydrogen; Pressurizing gas: Nitrogen

Analytical conditions:

• GC oven: 40°C (3 min), headspace oven: 65°C (20 min)
• Sample preparation: 480 µL blood or water, 20 µL spiking standard (ethanol), 100 µL internal standard (tert-butanol)
• Injection: split 1:13, hydrogen flow at constant linear velocity (60 cm/s), FID at 250°C
• Pre-conditioning: injection of highly concentrated ethanol and tert-butanol, followed by blanks to prevent carry-over

Key Results and Discussion

Calibration and linearity:

• Six-point calibration for ethanol (20–500 mg/dL) in water and blood matrices with correlation coefficients (R²) > 0.999 for both columns
• Blood matrix increased slopes slightly due to matrix effects on headspace equilibrium

Repeatability:

• Peak area stability with %RSD <1.3% on repeated standard injections
• Quantification errors within ±10% for spiked concentrations across both calibration curves

VOC separation:

• Baseline separation of seven VOCs (methanol, acetaldehyde, ethanol, 2-propanol, acetone, tert-butanol, 1-propanol) within 2.4 min
• Distinct separation profiles on the two columns confirm cross-validation potential

Benefits and Practical Applications

• Compact dual-column GC reduces laboratory footprint by about 35% compared to conventional systems
• Dual FID detection ensures cross-checked results, enhancing reliability in forensic and clinical analyses
• Use of hydrogen carrier gas shortens run time, improving sample throughput

Future Trends and Applications

• Integration of advanced detectors (e.g., mass spectrometry) for expanded analyte range
• Automation and data-processing algorithms tailored for high-volume forensic laboratories
• Miniaturization and networking of GC systems for mobile or point-of-care testing
• Application to other VOC monitoring scenarios (environmental, food safety, industrial hygiene)

Conclusion

The dual-column Brevis GC-2050 coupled with HS-20 NX delivers rapid, reliable BAC analysis within a compact footprint. High linearity, excellent repeatability, and full VOC separation demonstrate its suitability for forensic and clinical toxicology. Adoption of hydrogen as carrier gas further enhances throughput, making this system a versatile solution for modern laboratories.