Pyrolysis and thermal extraction of polymeric materials with suction-driven, real-time ionization sources and rapid polarity switching, high resolution mass spectrometry

Abstract

Real-time sampling systems are assembled for analysis of pyrolyzed material using in-line ionization and high resolution mass spectrometry. Two commercial models of Pyroprobe pyrolyzer with either a wand-mounted coil or a drop-in sample chamber are reconfigured from the standard gas chromatograph interface. Either a flow cell containing a platinum coil or a drop-in pyrolysis chamber is connected to a heated transfer line that conducts pyrolysates directly to a photoionization or dielectric barrier discharge source. The ion source is mounted to the front of an Orbitrap system, drawing analyte through from the pyrolyzer using instrument vacuum and/or supplementary pumping. The mass spectrometer scans in rapidly-alternating polarity so that positive and negative mode analyses are acquired in a single run. Pyrolyzed samples of tens of micrograms of polymeric materials yielded robust and resolved signal, especially from halogenated ions in negative mode that otherwise did not produce enough electron impact ionization signal for identification. The photoionization source in particular was easily purged of lingering pyrolysate by temporarily increasing the supplemental flow rate, rapidly returning signal to baseline levels after an analytical run. Elimination of carryover allowed replicate analyses to be collected at a rate of every 2 min without an autosampler. Slow-ramp thermal extraction analyses was performed on the same system as flash pyrolysis without any change in hardware.