The Composition of Poly(Ethylene Terephthalate) (PET) Surface Precipitates Determined at High Resolving Power by Tandem Mass Spectrometry Imaging.

We present the first demonstration of a general method for the chemical characterization of small surface features at high magnification via simultaneous collection of mass spectrometry (MS) imaging and tandem MS imaging data. High lateral resolution tandem secondary ion MS imaging is employed to determine the composition of surface features on poly(ethylene terephthalate) (PET) that precipitate during heat treatment. The surface features, probed at a lateral resolving power of<200 nm using a surface-sensitive ion beam, are found to be comprised of ethylene terephthalate trimer at a greater abundance than is observed in the surrounding polymer matrix. This is the first chemical identification of PET surface precipitates made without either an extraction step or the use of a reference material. The new capability employed for this study achieves the highest practical lateral resolution ever reported for tandem MS imaging.