Characterization of Persistent Organic Pollutants in Suspended Sediments by Thermal Desorption Coupled to GC×GC-TOFMS

Significance of the Topic

The monitoring of persistent organic pollutants (POPs) in suspended sediments is critical for assessing long-term environmental impacts on the Great Lakes ecosystem, particularly from historical industrial discharges and contaminated sites.

Objectives and Study Overview

This study aimed to broaden the screening scope beyond the routine list of 21 PAHs and related organochlorines entering Lake Ontario via the Niagara River and to eliminate complex wet chemistry cleanup steps prior to analysis.

Methodology

Homogenized sediment samples (~20 mg) were thermally desorbed using a programmed ramp from 50 °C to 300 °C and transferred directly into a GC inlet held initially at 35 °C, followed by a temperature gradient to 320 °C.

Used Instrumentation

• CDS Analytical Pyroprobe 5200 for thermal desorption
• GC×GC system with Restek Rxi-5MS (30 m×0.25 mm×0.25 µm) first-dimension column and Rxi-17SilMS (1.5 m×0.25 mm×0.25 µm) second-dimension column, 3 s modulation
• Pegasus 4D time-of-flight mass spectrometer operating at 200 spectra/s over m/z 45–1000

Results and Discussion

The comprehensive two-dimensional separation resolved complex coelutions, enabling spectral deconvolution and library matching.
Over 120 PAHs and alkyl homologs were identified—more than 100 additional compounds compared to the routine monitoring list.

Benefits and Practical Applications

The direct thermal desorption approach removed the need for solvent-intensive cleanup, reduced analysis time, and enhanced the detection of trace-level contaminants in sediment matrices.
Environmental laboratories can apply this workflow to improve the breadth and speed of POP monitoring.

Future Trends and Applications

Further integration of high-resolution mass spectrometry could characterize unknown peaks indicated by library-search markers.
The method could extend to other environmental compartments and support field-deployable GC×GC platforms for on-site analysis.

Conclusion

Thermal desorption coupled with GC×GC-TOFMS offers a powerful, streamlined workflow for expanded POP screening in suspended sediments, delivering superior compound coverage and eliminating extensive wet-chemical preparation.

References

Byer JD, Hill B, Binkley J Characterization of Persistent Organic Pollutants in Suspended Sediments by Thermal Desorption Coupled to GC×GC-TOFMS