Spatially resolved in-situ analysis of polymer additives by two-step laser mass spectrometry

Two-step laser mass spectrometry has been employed for the direct in-situ analysis of a variety of additives in different polymers. Because of the high sensitivity and optical selectivity of this approach, mass spectra can be obtained directly from the polymer material. The effects of CO2 laser irradiation (lambda=10.6 mu m) on samples of poly(oxymethylene) (POM), poly(vinyl chloride) (PVC), polypropylene (PP), and poly(ethylene terephthalate) (PET) and the mechanism of additive desorption have been examined. Several hydroxyphenylbenzotriazole (Tinuvin) UV stabilizers as well as a phenolic antioxidant (Santo White) were successfully detected in typical industrial polymers. The detection limit for Santo White antioxidant in POM was found to be as low as 28 ppm. Finally, depth profiling by stepwise CO2 laser ablation was carried out for a POM injection bar containing 0.1 wt % antioxidant. These spatially resolved measurements established that the near surface concentration of antioxidant was 40% lower than in the bulk.