Large Volume Injection of Organochlorine Pesticide Extracts Using a Programmable Temperature Vaporizer in the Solvent Split Mode

Importance of topic

Organochlorine pesticides are persistent environmental contaminants with health risks at trace levels. Analytical methods must maximize sensitivity and minimize thermal degradation. Programmable temperature vaporizer solvent split injection addresses these challenges by enabling large volume sample introduction without overloading the injector or compromising analyte integrity.

Objectives and overview of the study

This work evaluates 100 ul solvent split injections using an Optic PTV compared to conventional 1 ul cold splitless injections. Linearity, sensitivity and thermal breakdown are assessed for a range of organochlorine pesticides.

Methodology and instrumentation

• Gas chromatograph Carlo Erba 8560 with electron capture detector
• Programmable temperature vaporizer injector Optic PTV by Tekmar Dohrmann
• DB 35 capillary column 30 m by 0.53 mm id with 0.5 um film
• Helium carrier gas at 30 cm/s linear velocity
• Cold splitless injection: 1 ul, PTV initial 50 C, ramp 4 C/s to 275 C, splitless time 2 min, split flow 170 ml/min
• Solvent split mode: 100 ul, PTV initial 30 C, ramp 16 C/s to 275 C, splitless time 37 s, split flow 50 ml/min, split time 113 s

Main results and discussion

Cold splitless injections over 5 to 80 ng/ml yielded an average RSD of 7 percent. Solvent split injections over 0.1 to 1.6 ng/ml showed an average RSD of 8 percent. Chromatograms revealed a 100-fold sensitivity gain with solvent split mode and detection down to 0.1 ng/ml. Thermal degradation of Endrin was reduced to 0.5 percent compared to 11 percent under hot splitless conditions, while DDT breakdown remained low at 4.4 percent versus 3.6 percent.

Benefits and practical applications

• Enhanced sensitivity via large volume injections
• Improved detection limits down to 0.1 ng/ml
• Reduced thermal degradation of labile pesticides
• Capability to handle complex or dirty samples
• Simple manual injection of 100 ul without complex autosampler operation

Future trends and potentials

Further developments may include automated large volume injection workflows, integration with mass spectrometric detection, application to diverse analyte classes, optimized protocols for highly volatile compounds, and miniaturized PTV designs to broaden analytical capabilities in environmental monitoring and regulatory testing.

Conclusion

Solvent split large volume injections using a programmable temperature vaporizer provide a straightforward method to increase gas chromatographic sensitivity by two orders of magnitude while maintaining linearity and minimizing thermal degradation of organochlorine pesticides.

References

1. Grob Th Laubli and B Brechbuhler J High Res Chromatogr 11 1988 462 470
2. Stafford Electronic Pressure Control in Gas Chromatography Hewlett Packard Company 1993
3. Mol H G Janssen and C Cramers J High Res Chromatogr 18 1995 19 27