Agilent Inert Flow Path Enhancements Improve Drugs of Abuse Testing

Importance of the Topic

Gas chromatographic analysis of drugs of abuse demands extremely low surface activity in the flow path to prevent adsorption and ensure accurate detection at trace levels. Inert components minimize active sites, improving peak shape, sensitivity and quantitation critical for forensic and toxicology laboratories.

Objectives and Study Overview

This evaluation compares Agilent UltiMetal Plus Flexible Metal ferrules versus standard Siltite ferrules in a post-column Ultimate Union using GC/FID, alongside an inert split/splitless inlet versus a standard inlet on GC/MS (SCAN and SIM) for a 28-component forensic/toxicology checkout mix.

Methodology and Instrumentation

• Forensic/toxicology mix: 28 compounds at 1 ng/component with triphenyl phosphate internal standard.
• GC/FID setup: Agilent 7890 GC with FID detector, 7693 ALS, single split/splitless inlet, Ultimate Union with interchangeable ferrules.
• GC/MS setup: Agilent 7890 GC coupled to 5975C MSD, inert split/splitless inlet versus standard inlet, same HP-5ms UI column, SCAN (40–450 amu) and SIM targeting benzodiazepines.
• Identical chromatographic conditions ensured direct comparison.

Used Instrumentation

• Agilent 7890 Gas Chromatograph
• Agilent 5975C Mass Selective Detector (triple-axis)
• Agilent 7693 Automatic Liquid Sampler
• Agilent J&W HP-5ms UI column (30 m × 0.25 mm, 0.25 µm)
• Ultimate Union capillary flow connector
• UltiMetal Plus Flexible Metal ferrules and Siltite ferrules
• Split/splitless inlet liners and Ultra Inert gold seals
• FID detector with hydrogen/air makeup gases

Main Results and Discussion

• GC/FID: UltiMetal Plus ferrules delivered sharper, more intense benzodiazepine peaks (nitrazepam, clonazepam, temazepam) compared to Siltite at 1 ng on-column.
• GC/MS SCAN: Inert inlet preserved benzodiazepine peaks at 0.5 ng, while the standard inlet lost low-level analytes (temazepam undetected).
• GC/MS SIM: At 0.25 ng, the inert inlet clearly detected temazepam, nitrazepam, clonazepam and alprazolam, all of which were broadened or absent with the standard inlet.
• Inert flow path components reduced active surface interactions, enhancing detection limits and quantification accuracy for active analytes.

Benefits and Practical Applications

• Improved sensitivity and peak shape for trace-level drugs, essential in forensic/toxicology screening.
• Enhanced reproducibility and quantitative accuracy for benzodiazepine analysis.
• Easy retrofitting of inert components into existing GC/FID and GC/MS platforms.

Future Trends and Applications

Adoption of fully inert flow path solutions will continue, enabling detection of emerging psychoactive substances at ever lower levels. Advances in surface deactivation and novel inert materials will support high-throughput forensic, clinical and environmental analyses.

Conclusion

UltiMetal Plus Flexible Metal ferrules and an inert GC/MS inlet significantly enhance peak shape and response for benzodiazepines and other active drugs at trace concentrations. Implementing these inert components boosts sensitivity, reliability and quantitation in forensic/toxicology workflows.

References

• Lynam K. Semivolatile Analysis Using an Inertness Performance Tested Agilent J&W DB-5ms Ultra Inert Column. Agilent Technologies Application Note. 2008;5989-8616EN.
• Zhao L, Broske A, Mao D, Vickers A. Evaluation of the Ultra Inert Liner Deactivation for Active Compounds by GC. Agilent Technologies Technical Overview. 2011;5990-7380EN.
• Agilent Technologies. Optimize your GC flow path for inertness. Poster. 2013;5990-8902EN.