Testing the Performance of the Focus Direct-TD with Real Samples

Significance of the Topic

Automated thermal desorption offers high-throughput analysis of volatile and semi-volatile compounds with minimal manual intervention. The Focus Direct-TD system streamlines sample handling, reduces operator error, and enhances reproducibility in laboratories performing environmental monitoring, food analysis, and quality control.

Objectives and Study Overview

This application note evaluates the analytical performance of the Focus Direct-TD when processing real samples. Three experimental series were designed:

• Experiment 1: Assess linearity, precision, and carryover using triethyl phosphate (TEP) spiked SepLiners.
• Experiment 2: Determine volatile loss from biological matrices (rosemary and broad bean leaves) held in the sample tray over time.
• Experiment 3: Evaluate potential contamination of liners and the injector from laboratory air during automated tube exchanges.

Instrumentation Used

• ATAS Optic 2-200 programmable injector
• ATAS Focus Autosampling Robot with Direct-TD option
• Agilent 5890 GC equipped with FID detector

Methodology and Instrumentation

Pre-conditioned SepLiners containing 50 mg Porapak were spiked with TEP at concentrations between 4.375 and 70 ppm. Automated desorption and GC–FID analysis provided calibration and precision data. For matrix experiments, headspace samples from rosemary (high volatiles) and broad bean (low volatiles) leaves were run immediately and after 16 hours in the tray. Contamination tests exposed injector and tray liners to open solvent bottles for two hours under normal lab conditions.

Main Results and Discussion

• Linearity: Calibration between 4.375 and 70 ppm TEP yielded R² ≈ 0.999, indicating negligible sample loss in the tray.
• Precision: RSDs of four injections on day 1 (2.7%) and six on day 2 (3.5%) remained well below the 4% threshold.
• Carryover: No detectable transfer from sample tray for 70 ppm TEP; neat TEP showed <0.5% carryover persisting over 19 hours.
• Volatile retention: Chromatograms of rosemary and broad bean samples before and after 16 hours exhibited minimal peak area differences, confirming low analyte loss.
• Contamination: No solvent peaks appeared in injector blanks after automated exchanges; packed liners in the tray showed negligible adsorbed laboratory volatiles.

Benefits and Practical Applications

The Focus Direct-TD system delivers robust, reproducible thermal desorption workflows with low carryover and contamination risk. It supports trace-level quantitation, extended unattended operation, and reliable handling of diverse matrices in environmental, food, and industrial laboratories.

Future Trends and Applications

Advances in sorbent materials and automated sampling protocols will further expand the applicability of Direct-TD systems to heavier semi-volatile compounds and complex matrices. Integration with high-resolution mass spectrometry and software-driven QA/QC routines promises deeper sample insights and improved laboratory productivity.

Conclusion

Comprehensive testing confirms that the Focus Direct-TD provides linear, precise, and contamination-free thermal desorption for real-world samples. Its automated tube exchange and robust design make it a valuable tool for high-throughput volatile analysis.

References

1. Nicholas, D. Application Note No. 063: Testing the Performance of the Focus Direct-TD with Real Samples. GL Sciences B.V., Eindhoven, The Netherlands.