Analysis of Drug Facilitated Sexual Assault (DFSA) Drugs by Gas Chromatography-Time-of-Flight Mass Spectrometry

Importance of the Topic

The analysis of drug facilitated sexual assault (DFSA) cases is critical for forensic and clinical investigations. Victims often present urine samples containing trace levels of sedatives, narcotics, stimulants and other compounds with short elimination half-lives. Employing a rapid and sensitive approach ensures timely support for victims and reliable evidence for legal proceedings.

Objectives and Study Overview

This study aimed to evaluate gas chromatography-time-of-flight mass spectrometry and automated mass spectral deconvolution for screening DFSA drug compounds in anonymized urine samples. By creating a custom reference library and using automated peak detection, the researchers sought to reduce manual review times while maintaining high confidence in compound identification.

Methodology and Sample Preparation

Anonymous urine extracts from alleged assault victims were prepared via liquid-liquid extraction. Four stable internal standards were added before extraction. The organic layer was dried and reconstituted in an isooctane: dichloromethane: ethanol mixture. Twenty-four case study samples and three positive control standards were processed under identical conditions before GC-TOFMS analysis.

Instrumentation Used

• Gas Chromatograph: 7890 model with splitless injection, Phenomenex ZB-DRG1 column (10 m×0.18 mm×0.18 μm).
• Carrier Gas: Helium with ramped flow profile.
• Oven Program: Initial hold at 40 °C, rapid ramp to 280 °C, total run around 16.8 min.
• Mass Spectrometer: Time-of-flight system with electron impact ion source at 70 eV, acquisition rate 20 spectra/s over mass range 30–500 m/z.
• Data Software: ChromaTOF version 4.24 with automated peak find and custom reference library functions.

Main Results and Discussion

Of the 24 case samples, 16 (67 %) contained at least one potential DFSA compound. The custom reference library included more than 50 target drugs spanning stimulants, benzodiazepines, antidepressants, opioids and antihistamines. Automated peak detection and deconvolution successfully identified co-eluting analytes such as diazepam and norcodeine in high-matrix urine extracts. Mass spectral matching criteria of 700 match score and retention time tolerance of 3 s ensured high confidence in positive identifications.

Benefits and Practical Applications

This approach offers several advantages for forensic laboratories:

• Rapid data review: Approximately 30 s per sample compared to one hour with manual methods.
• Comprehensive screening: Full mass range acquisition allows detection of non-target compounds as well as library targets.
• High sensitivity: Low picogram detection limits facilitate analysis of compounds with short half-lives.
• Reduced false positives: Combined retention time and spectral match criteria improve specificity.

Future Trends and Possibilities for Use

Advances in time-of-flight instrumentation and library development will support broader drug panels and shorter chromatography times. Integration with high-throughput sample preparation and machine learning-based spectral deconvolution may further accelerate case workflows. Emerging designer drugs and novel psychoactive substances will require dynamic updates to reference databases.

Conclusion

GC-TOFMS combined with automated mass spectral deconvolution provides a fast, sensitive and reliable platform for screening urine samples in DFSA investigations. The method significantly reduces analyst workload and delivers high-confidence identifications, reinforcing its suitability for forensic laboratories.

References

• L. Slaughter. Involvement of drugs in sexual assault. J. Reprod. Med. 45: 425-430 (2000).
• M.A. ElSohly and S.J. Salamone. Prevalence of drugs used in cases of alleged sexual assault. J. Analytical Toxicol. 23: 141-146 (1999).