Analysis of Microplastics Samples Using Pyrolysis Gas Chromatography Mass Spectrometry

Significance of the Topic

Microplastic and nanoplastic pollution in aquatic environments poses ecological and health risks through bioaccumulation in fish and shellfish. Conventional spectroscopic methods may be hindered by dyes and additives. Pyrolysis gas chromatography–mass spectrometry (Py–GC/MS) offers a robust approach to polymer identification, even in complex matrices.

Aims and Study Overview

This study demonstrates the application of a GERSTEL Multipurpose Sampler (MPS) with Thermal Desorption Unit (TDU), programmable temperature vaporizer (CIS 4), and TDU PYRO insert for identifying microplastics from Great Lakes samples and commercial personal care products. It evaluates both fractionated pyrolysis and Smart Ramped Pyrolysis (SRP) modes to streamline method development and enhance compound resolution.

Methodology and Instrumentation

The workflow combined two pyrolysis strategies:

• Fractionated pyrolysis at 120 °C, 300 °C, and 600 °C to separate low- and high-temperature degradation products.
• Smart Ramped Pyrolysis (SRP) with a 5 °C/s ramp from 300 °C to 800 °C to minimize secondary reactions and obviate multiple runs.

Sample preparation involved loading <1 mg of plastic or aqueous sediment onto quartz tubes with quartz wool. Chromatographic separation used a 30 m DB-5MS UI column with helium at 1 mL/min, oven program 40 °C to 320 °C. Mass spectra provided polymer-specific fragment patterns.

Instrumentation Used

• GERSTEL MPS Robotic Sampler
• GERSTEL Thermal Desorption Unit (TDU) 2 with PYRO insert
• GERSTEL CIS 4 inlet (solvent vent and split modes)
• Agilent 30 m DB-5MS UI column, 0.25 mm i.d., 0.25 µm film
• GC/MS system equipped with EI ionization

Main Results and Discussion

Plastic particles from Great Lakes samples were identified as polyethylene and polypropylene, including mixed PE/PP in some colors. Fractionated pyrolysis showed glycerol and cosmetic additives at 120 °C, long-chain acids and siloxanes at 300 °C, and polyethylene fragments at 600 °C. Sediment extracts yielded styrene, methyl methacrylate, siloxanes, Bis(2-ethylhexyl) phthalate and phthalic anhydride. A commercial facial scrub displayed a complex profile dominated by polystyrene and polyethylene beads along with cosmetic ingredients.

Benefits and Practical Applications

SRP mode reduces method development time by generating optimal pyrograms in a single run. Fractionated pyrolysis simplifies chromatograms, aiding identification of co-eluting components. The approach handles minute masses and aqueous suspensions, making it suitable for environmental monitoring, quality assurance in personal care, and regulatory compliance.

Future Trends and Potential Applications

• Integration with spectral libraries and automated polymer recognition algorithms.
• High-throughput workflows for large-scale environmental screening.
• Coupling with chemometric data analysis for quantitative assessments.
• Portable or field-deployable Py–GC/MS systems for on-site monitoring.

Conclusion

The GERSTEL MPS/TDU/CIS configuration with the TDU PYRO insert effectively identifies microplastics in environmental and commercial samples. Smart Ramped Pyrolysis and fractionated approaches streamline analysis, reduce sample consumption, and enhance detection of diverse polymer types and additives.