Sub-Picogram Detection and Identification of Analytes in Complex Matrices Using a Novel GC-TOFMS

Significance of the Topic

Improved sensitivity and dynamic range in gas chromatography–time-of-flight mass spectrometry (GC-TOFMS) enable detection of sub-picogram analytes in complex samples, reducing sample preparation and expanding trace-level applications in environmental, food, and forensic analysis.

Objectives and Study Overview

This work evaluates the performance of the Pegasus BT GC-TOFMS system (LECO) for ultra-trace analysis, focusing on instrument detection limits (IDLs), linear dynamic range, reproducibility, and mass stability in both solvent standards and a black tea matrix extract.

Instrumental Setup

The Pegasus BT features:

• An open-style electron ionization source positioned to minimize surface contamination effects.
• Robust ion optics and a high-performance reflectron mass analyzer.
• A custom data acquisition system with dual 500 MHz 12-bit ADCs generating low- and high-gain data streams combined into 15 bits of vertical resolution.
• Two-dimensional deconvolution algorithms applied across retention time and time-of-flight dimensions to achieve sub-nominal mass accuracy.

Methodology

Multi-analyte mixtures of 14 compounds were prepared in methylene chloride at concentrations from 1.25 pg/µL to 25 ng/µL and spiked into QuEChERS tea extracts. GC separations used an RXI-5MS column with split injection ratios of 20:1 or 100:1. Oven programs ranged from 35 °C (1 min) to 330 °C (5 min) at 20 °C/min. Transfer line and source temperatures were 320 °C and 300 °C (or 250 °C for OFN), respectively. Data were acquired over m/z 35–640 at 10 spectra/s.

Main Results and Discussion

• Detection Limits: Solvent-based IDLs ranged from ~9 fg to ~30 fg per analyte (eight replicates at 62.5 fg on column). In tea matrix, eight analytes achieved sub-20 fg IDLs, demonstrating excellent sensitivity.
• Dynamic Range: Linear response covered five orders of magnitude (25 fg to 2.5 ng) with correlation coefficients >0.99 for all compounds.
• Reproducibility and Mass Stability: Over eight days of 500 fg OFN injections, peak area %RSD was 4.3% without source cleaning or recalibration, confirming robust long-term stability.
• Deconvolution Performance: Two-dimensional deconvolution effectively separated molecular ions from column bleed interferences, even for high-mass alkanes.

Benefits and Practical Applications

• Trace-level monitoring in environmental, food safety, and forensic laboratories.
• Reduced sample consumption and simplified preparation via split injection.
• High throughput enabled by extended maintenance intervals and stable long-term operation.

Future Trends and Opportunities

Integration of GC-TOFMS with automated sample handling and artificial intelligence–driven data analysis will further streamline workflows. Advancements in real-time field deployable instruments and enhanced non-targeted screening algorithms are poised to expand applications in clinical diagnostics and emergency response.

Conclusion

The Pegasus BT GC-TOFMS demonstrates sub-picogram detection limits, five orders of dynamic range, and outstanding reproducibility in complex matrices, marking a significant advancement for ultra-trace analysis across diverse analytical fields.

References

• No literature references were provided in the source text.