Reduction of Endrin and DDT Breakdown Using a PTV Injector

Importance of the Topic

Accurate determination of persistent organochlorine pesticides such as endrin and DDT is essential for environmental monitoring and compliance with regulatory methods. Thermal degradation in conventional GC injection ports can lead to underestimation of analyte concentrations and the formation of breakdown products that interfere with quantification.

Objectives and Overview of the Study

This work examines the use of a Programmed Temperature Vaporizing (PTV) injector in cold splitless mode to minimize breakdown of endrin and DDT. The study compares traditional hot splitless injections with cold‐ramped injections, evaluating percent degradation under clean and residue‐loaded conditions.

Methodology and Used Instrumentation

The investigation employed two injection modes with a Tekmar OPTIC PTV injector coupled to a Carlo Erba HRGC Mega 2 GC fitted with an XTI‐5 capillary column and Electron Capture Detector. Key parameters:

• Hot splitless: 275 °C isothermal injector
• Cold splitless: ramp from 95 °C to 275 °C at 4 °C/sec, 10 min hold
• Oven program: 150 °C initial, 8 °C/min to 275 °C, 5 min hold
• Carrier gas: Helium at 8 mL/min

Residue buildup was simulated by daily injections of hexane‐extracted soil over one week.

Main Results and Discussion

In hot splitless mode, endrin and DDT breakdown ranged from approximately 8 % up to over 40 % as residue accumulated. Cold splitless injection reduced degradation to below 10 % for both analytes, even after extensive liner fouling. The solvent vaporization in the cold injector masked active sites, limiting analyte–surface interactions and preserving molecular integrity.

Benefits and Practical Applications

• Maintains degradation below the 20 % threshold specified by EPA Method 8080
• Extends injector maintenance intervals by minimizing residue‐induced breakdown
• Improves accuracy in trace pesticide analysis for soil and environmental samples

Future Trends and Possibilities

Advances in PTV injector designs and specialized liner coatings promise further reduction of active sites and improved thermal control. Integration with automated cleaning cycles and application to other thermally labile residues will expand method robustness. Emerging detectors and real‐time monitoring may offer deeper insight into on‐line degradation phenomena.

Conclusion

Cold splitless PTV injection provides a simple and effective strategy to reduce endrin and DDT breakdown during GC analysis. By introducing the sample at low temperature and ramping to vaporization, this approach preserves analyte integrity, meets regulatory requirements, and reduces instrument downtime.

Reference

U.S. Environmental Protection Agency. Method for the Determination of Organochlorine Pesticides and PCBs, EPA-8080 (1986).