A Selective Electrochemical Gas Chromatography Detector Based on Axial Ligation Reactions of a Molten Iron Porphyrin Redox Polyether Hybrid

摘要

An iron tetraphenylporphyrin, with four appended, oligomeric (MW = 550), poly(ethylene glycol) chains ([Fe-(T550PP)CI]), is an electroactive, room-temperature melt, and undergoes axial coordination with volatile bases, such as pyridines, when they are partitioned at a gas/melt interface into a film of the porphyrin. The Fe(III/II) reaction of the axially coordinated porphyrin can be used amperometrically as a means of detecting the pyridine vapor, as shown in plug flow experiments with open tubular columns. The mechanism of the ECGC detector response is analyzed. This detection scheme is minimally responsive or nonresponsive to gaseous analytes that do not coordinate to the Fe(III) state of the porphyrin. The detector's selective response to pyridine is linear over a 500-fold range but is not yet very sensitive in comparison to the (nonselective) flame ionization detector. The ECGC detector has utility in detecting weak ligand interactions with the porphyrin (i.e., alcohols), and its response also detects slow dissociation rates of the Fe(II) complex formed in the detection reaction.