Analysis of Drugs by GC/MS using the Ultra Inert Inlet Liners with Wool

Significance of the topic

Gas chromatography–mass spectrometry (GC–MS) is a cornerstone technique in forensic toxicology for screening drugs of abuse. The inlet liner plays a critical role in sample vaporization, mixing, and protection of the analytical column and detector. Liners packed with glass wool enhance sample homogenization and trap nonvolatile residues, but inadequate deactivation of the glass surface can lead to adsorption, decomposition, and chromatographic artifacts. The development of highly inert inlet liners is therefore essential to achieve reliable, reproducible detection of a broad range of basic drug compounds.

Objectives and overview of the study

This application note evaluates Agilent’s Ultra Inert splitless inlet liners packed with glass wool for the GC–MS screening of 28 popular and challenging basic drugs. The study compares chromatographic performance, sensitivity, liner-to-liner reproducibility, and multi-injection stability against other commercially available wool liners. Both neat standards and complex biological matrices are tested to assess real-world applicability.

Methodology and instrumentation

Samples were prepared using an Agilent forensic-toxicology checkout mixture containing 28 basic analytes at concentrations of 5 μg/mL and 0.5 μg/mL in a 90/5/5 toluene/methanol/acetonitrile solvent. An internal standard mix was spiked to achieve 2 μg/mL. GC–MS analysis employed an Agilent 7890A GC with a 7683B autosampler and a 5975C MSD, using a 15 m × 0.25 mm DB-5MSUI column. The inlet was operated in splitless mode at 280 °C with a helium carrier gas at constant pressure. Selected ion monitoring (SIM) and full-scan acquisition (40–570 amu) were used to evaluate peak response and shape. Retention time locking and back-flushing were implemented to enhance robustness.

Main results and discussion

Ultra Inert liners with wool delivered significantly improved peak shapes and higher responses for early-eluting and late-eluting compounds compared to competitor liners, which exhibited peak tailing, broadening, and ghosting. Liner-to-liner reproducibility assessed across six liners from four production lots showed response-factor RSDs below 7 % for most analytes, except temazepam (≈12 %). Multi-injection repeatability over 50 injections (0.5 ng on column) yielded RSDs below 20 % for 22 of 28 analytes, demonstrating deactivation stability. Analysis of a spiked whole-blood extract (2 ppm) confirmed that Ultra Inert liners maintain chromatographic integrity in high-matrix samples.

Benefits and practical applications

• Enhanced inertness minimizes adsorption and thermal decomposition of basic drugs.
• Improved peak shape and sensitivity across a broad retention range.
• Excellent liner-to-liner consistency and injection repeatability.
• Extended column life and reduced MS source maintenance via nonvolatile residue trapping.
• Suitable for high-throughput forensic screening with minimal sample cleanup.

Used instrumentation

• Agilent 7890A GC with splitless Ultra Inert inlet liners (p/n 5190-2293).
• Agilent 7683B autosampler (1 μL injections).
• Agilent 5975C MSD with performance electronics.
• DB-5MSUI column, 15 m × 0.25 mm, 0.25 μm film.
• Helium carrier gas, retention time locking, and back-flush configuration.

Future trends and possibilities

Advances in inlet liner technology will play a key role in the analysis of emerging psychoactive substances and highly polar drug derivatives. Integration with high-resolution MS, automation of liner exchange, and miniaturized sample introduction are potential directions. Highly inert surfaces may also benefit environmental and clinical analyses where trace detection and matrix complexity are critical.

Conclusion

Agilent’s Ultra Inert inlet liners packed with glass wool offer superior inertness, reproducibility, and stability for GC–MS screening of basic drugs. By combining efficient deactivation with the advantages of wool packing, these liners enhance analytical performance, reduce maintenance, and support robust high-throughput forensic toxicology workflows.

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. Seyhan N., Ege D.C. Organic Chemistry. Health and Company; 1984.
3. Szelewski M., Quimby B. New Tools for Rapid Pesticide Analysis in High Matrix Samples. Agilent Technologies, 5989-1716EN.
4. Wylie P., Meng C. A Method for the Trace Analysis of 175 Pesticides Using the Agilent Triple Quadrupole GC/MS/MS. Agilent Technologies, 5990-3578EN.
5. Giarrocco V., Quimby B. Retention Time Locking: Concepts and Applications. Agilent Technologies, 5966-2469EN.