Thermal decomposition behaviors of a series of imidazolium-type ionic liquid samples were studied by pyrolysis-gas chromatography at 550˚C using various detectors. As for the imidazolium halides, haloalkanes and 1-alkylimidazoles corresponding to the alkyl substituents were mainly formed through the nucleophilic attacks of halide ions to the alkyl groups followed by C-N bond cleavage, along with a minor amount of alkenes. Meanwhile, in the case of the ionic liquids with BF4, PF6 and CF3SO3 anions, corresponding alkenes were predominantly produced along with 1-alkylimidazoles rather than haloalkanes. No boron-containing products were found even from the samples with BF4 anion, whereas minor but clear peaks of phosphorous-containing products were observed in the pyrograms of the samples with PF6 anions. As for the samples with longer alkyl group, the pyrolyzates reflecting the C-C bond scissions in the alkyl groups were also formed to some extent. Meanwhile, imidazole rings did not decompose under the experimental conditions at around 550˚C.

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Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a novel elemental analysis method where a sample solution is placed in a small cuvette that has a narrow microchannel at the center. High voltage is applied to the solution from both ends of the cuvette channel, and then microplasma is generated in the channel. The microplasma is employed in atomic emission spectrometry as a plasma source. Excitation temperature was deduced using a Boltzmann plot. The temperature was determined to be 6200 K with a plastic chip at an applied voltage of 800 V. To investigate effects of the experimental conditions on excitation temperature, applied voltage, type of acid, and the shape of the cross section of a microchannel at the center of the cuvette were varied. The excitation temperature was not influenced by applied voltage or type of acid, but was affected by the shape of the cross section of the microchannel.