UV laser pyrolysis fast gas chromatography/time-of-flight mass spectrometry for rapid characterization of synthetic polymers: optimization of instrumental parameters

摘要

The effects of nine experimental factors on the production and distribution of pyrolysis products from a model polymer (polyethylene) generated by laser pyrolysis-gas chromatography/mass spectrometry (LPy-GC/MS) have been studied. The instrument uses a computer controlled, Q-switched Nd: YAG laser, frequency quadrupled to 266 run, coupled to a fast gas chromatograph and time-of-flight (TOF) mass spectrometer. Factors varied in designed experiments include: flow rate through the sample cell, frequency of the laser, number of laser spots, number of laser shots, laser spot size, laser energy, cold trapping time, cold trapping temperature, and sample cell temperature. The resulting operational understanding of the behavior of the laser pyrolysis system has enabled tuning of the numerous experimental variables so that both low and high molecular pyrolysis products are transferred to the GC/TOF-MS analysis system efficiently and reproducibly.