Toxicology Screening of Whole Blood Extracts Using GC/Triple Quadrupole/MS

Significance of the Topic

Effective toxicology screening of whole blood is critical in forensic and clinical settings to detect a wide range of drugs at low concentrations in complex biological matrices. Advances in gas chromatography coupled with triple quadrupole mass spectrometry (GC/QQQ) enable high sensitivity and selectivity, improving confirmation and quantitation of trace‐level analytes.

Objectives and Study Overview

This study aimed to evaluate the performance of the Agilent 7000A GC/QQQ system for screening and confirmatory analysis of multiple drugs in whole blood extracts. A comparative assessment was conducted against a single quadrupole GC/NPD/MSD/DRS platform to demonstrate the enhanced capabilities of GC/QQQ in low‐level detection and confirmation.

Methodology and Instrumentation

• Sample Preparation: Whole blood extracts prepared by single‐step liquid‐liquid extraction into toluene, evaporation, and reconstitution at one tenth of original volume. Samples provided by NMS Labs.
• Chemicals and Standards: Analytical reference drugs diluted in toluene to 1 ng/µL for tuning and product ion scans, and to 10–50 pg/µL for multiple reaction monitoring (MRM) calibration.
• Instrumentation: Agilent 7890A GC with capillary flow technology two‐way splitter and backflushing, coupled to Agilent 7000A triple quadrupole MS. Helium carrier gas; DB-5MS UI column (15 m × 0.25 mm, 0.25 µm); splitless injection at 280 °C; oven program from 100 °C to 325 °C.
• Detection Parameters: Up to four MRM transitions per compound optimized for collision energy. Retention time locking and MRM mode used to achieve sub‐picogram detection limits.

Main Results and Discussion

The GC/QQQ system achieved method detection limits (MDLs) generally in the low picogram range for most analytes, with 6-acetylmorphine at 50 pg. Key findings include:

• Codeine: Confirmed at ~150 pg in sample A by MRM, whereas single quadrupole screening yielded marginal qualifier ratios and match scores.
• Fentanyl: Selective MRM transitions allowed clear identification at ~150 pg despite limited high‐abundance ions, outperforming scan and SIM data subject to interferences.
• Methadone: High selectivity of GC/QQQ enabled unambiguous confirmation at ~170 pg, overcoming common interferences in scan mode.
• Oxycodone: Detected ~60 pg with clean qualifiers in GC/QQQ, whereas scan data lacked reliable confirmation due to low signal and matrix noise.
• Cocaine: Demonstrated sub‐picogram sensitivity with detection of ~0.7 pg in sample A, a level undetectable by the single quadrupole system.

Benefits and Practical Applications

• High throughput screening and confirmation of hundreds of drugs in a single run.
• Sub‐picogram sensitivity for trace‐level detection in complex blood matrices.
• Enhanced selectivity reduces false positives and interferences common to full‐scan or SIM methods.
• Complementary workflow combining broad‐spectrum screening (GC/NPD/MSD/DRS) and targeted GC/QQQ confirmation.
• Robust backflushing prolongs column life and maintains system performance for challenging forensic samples.

Future Trends and Applications

• Expansion of compound libraries and retention time locked databases to increase screening breadth.
• Integration with two‐dimensional GC techniques for additional chromatographic separation of complex matrices.
• Advanced data processing tools for automated deconvolution and confirmation in MS/MS workflows.
• Application in clinical toxicology, therapeutic drug monitoring, and anti‐doping analysis.
• Incorporation of ultrahigh sensitivity detectors and miniaturized systems for on‐site forensic testing.

Conclusion

The Agilent 7000A GC/QQQ system delivers superior sensitivity and selectivity for forensic toxicology screening of whole blood extracts, enabling reliable detection and confirmation of drugs at trace levels. When used alongside a single quadrupole screening platform, this approach offers a comprehensive solution for routine toxicological analysis.

References

1. Quimby B. Improved Forensic Toxicology Screening Using A GC/MS/NPD System with a 725-Compound DRS Database. Agilent Technologies, 5989-8582EN.
2. Fritch D.F., Quimby B.D. Confirmation of THC in Oral Fluids Using High-Resolution 2-D GC/MS. Agilent Technologies, 5989-5668EN.
3. Sandy C. Analysis of Complex Samples by GC/MS/MS – Pesticides in Marine Biota. Agilent Technologies, 5989-9727EN.