Event Title

Simple Pyrolysis Gas Chromatography of Automotive Paints

Location

Science Center, Bent Corridor

Start Date

10-2-2015 12:00 PM

End Date

10-2-2015 1:20 PM

Poster Number

11

Abstract

Pyrolysis gas chromatography (Py-GC-MS) is often used to characterize automobile paint in the crime laboratory. Pyrolysis refers to the breakdown of polymers into small molecules under high heat in an inert environment. Identifying the pyrolysis products enables the determination of the original polymer. Commercial pyrolyzers that attach to a GC-MS instrument provide automated and reproducible pyrolysis and injection of the gaseous products, but they are very costly (>$20,000). This makes Py-GC-MS inaccessible for many laboratories, particularly academic labs. Therefore, we developed a simpler, more cost-effective method. The polymeric sample (~0.2 mg) is placed in a bent glass pipet, with the tip of the pipet in ice-cold dichloromethane. With N2 gas flowing through the pipet, the sample is heated with a natural gas-air flame. Pyrolysis products are collected in the cold solvent, and the resulting solution is analyzed by GC-MS. Several commercial plastics (#1-6) were tested and produced chromatograms and pyrograms (summed mass spectra) that matched well to those in a chromatogram/spectral library of known polymers. Clearcoats and electrocoats of automobile paints that were distinguishable by IR spectrophotometry were also distinguishable by this method. Paint layers that appeared to be indistinguishable by IR can be differentiated by this method.

Major

Natasha Eklund, Chemistry and Biochemistry
Caroline Oehlerich, Neuroscience

Project Mentor(s)

Rob Thompson, Chemistry and Biochemistry

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Oct 2nd, 12:00 PM Oct 2nd, 1:20 PM

Simple Pyrolysis Gas Chromatography of Automotive Paints

Science Center, Bent Corridor

Pyrolysis gas chromatography (Py-GC-MS) is often used to characterize automobile paint in the crime laboratory. Pyrolysis refers to the breakdown of polymers into small molecules under high heat in an inert environment. Identifying the pyrolysis products enables the determination of the original polymer. Commercial pyrolyzers that attach to a GC-MS instrument provide automated and reproducible pyrolysis and injection of the gaseous products, but they are very costly (>$20,000). This makes Py-GC-MS inaccessible for many laboratories, particularly academic labs. Therefore, we developed a simpler, more cost-effective method. The polymeric sample (~0.2 mg) is placed in a bent glass pipet, with the tip of the pipet in ice-cold dichloromethane. With N2 gas flowing through the pipet, the sample is heated with a natural gas-air flame. Pyrolysis products are collected in the cold solvent, and the resulting solution is analyzed by GC-MS. Several commercial plastics (#1-6) were tested and produced chromatograms and pyrograms (summed mass spectra) that matched well to those in a chromatogram/spectral library of known polymers. Clearcoats and electrocoats of automobile paints that were distinguishable by IR spectrophotometry were also distinguishable by this method. Paint layers that appeared to be indistinguishable by IR can be differentiated by this method.