Online detection of the volatile intermediates evolved from moxa floss pyrolysis with photoionization mass spectrometry

Abstract

The dynamic processes of moxa pyrolysis were detected with an online synchrotron radiation photoionization mass spectrometry (SR-PIMS) under ambient pressure. The mass spectra at different temperatures (573–1073 K) as well as time-evolved profiles of volatile intermediate species were obtained in real-time. More than 70 species were identified, including hydrocarbons, nitrogen-, oxygen- and sulfur-containing compounds. The production of species was analyzed in a semi-quantitative way by comparing the intensity of each species. Most species exhibit the maximum relative intensities at 773 K such as phenols, which could have a positive effect on health with a certain quantity. Numbers of harmful substances, such as 1,3-butadiene, aldehydes and methanol were detected under different temperatures. Among them, aromatics compounds are sharply increased with increased temperature possibly due to the coalesce of small alkenes, while residential time of most species reduces with increased temperature. Therefore, controlling the moxibustion pyrolysis to a relatively lower temperature is beneficial during the therapy.