50 μL CSR-LVSI with 5 ng Nitrosamines, THF, and 1,4-Dioxane On-Column

Importance of the Topic

Trace-level nitrosamines and residual solvents such as tetrahydrofuran (THF) and 1,4-dioxane are highly regulated due to their potential carcinogenicity and toxicity. Reliable quantification at the low parts-per-billion level is critical for pharmaceutical quality control, environmental monitoring, and ensuring consumer safety.

Objectives and Overview of the Method

This study demonstrates a gas chromatography–mass spectrometry method in selected ion monitoring (SIM) mode for simultaneous determination of nine nitrosamines along with THF and 1,4-dioxane. The goal is to achieve sub–nanogram on-column detection limits with a single 50 µL splitless injection.

Methodology

Sample preparation involves diluting a standard mix of nitrosamines, THF, and 1,4-dioxane in dichloromethane at 0.1 µg/mL. A 50 µL splitless injection with a 1.5 minute hold delivers approximately 5 ng of each analyte on-column. Chromatographic separation is carried out on a 30 m Rxi-5Sil MS capillary column (0.25 mm ID, 1 µm film) with a 10 m guard column. The oven program ramps from 35 °C to 50 °C at 50 °C/min, holds, then increases to 320 °C at 11.12 °C/min. Helium is used as carrier gas at 5.08 mL/min.

Instrumentation Used

• GC System: Agilent 7890A
• MS Detector: Agilent 5975C MSD in SIM mode
• Injection Liner: Premium single taper with quartz wool
• Transfer Line Temperature: 320 °C; Ion Source: 230 °C; Quadrupole: 150 °C
• SIM Program: Four groups with target ions for each compound and dwell times of 25–40 ms

Main Results and Discussion

All nine nitrosamines and the two solvents elute between 10.0 and 18.0 minutes with baseline resolution. The SIM approach provides high sensitivity and selectivity, allowing detection of each target at 5 ng on-column. Toluene, identified as a minor contaminant, does not interfere with analyte quantitation. Method repeatability shows relative standard deviations below 5% for retention times and peak area.

Benefits and Practical Applications

• Ultra-sensitive detection of nitrosamines and volatile solvents in pharmaceutical and environmental samples
• Robust separation on a single column with a fast temperature program
• Reduced analysis time and solvent consumption
• Compliance with regulatory guidelines for genotoxic impurities

Future Trends and Opportunities

Advances in high-resolution mass spectrometry and micro-flow GC may further lower detection limits and improve throughput. Automated sample preparation and in-line enrichments could streamline workflows. Expanding the method to additional nitrosamine analogs and related impurities will enhance its applicability in emerging regulatory environments.

Conclusion

This GC-MS SIM method effectively quantifies trace nitrosamines alongside THF and 1,4-dioxane with high sensitivity, precision, and chromatographic resolution. Its straightforward sample preparation, rapid analysis, and robust performance make it well suited for routine quality control in pharmaceutical and environmental laboratories.