Detection of volatile organic compounds by temperature-programmed desorption combined with mass spectrometry and Fourier transform infrared spectroscopy

摘要

A temperature-programmed desorption(TPD)device connected to a mass spectrometer was used to detect volatile organic compounds from air samples.The main aim was to develop an analytical method,by which both non-polar and polar organic components can be detected in the same run.In TPD,the adsorbed compounds are desorbed from the resin more slowly than in the conventional trapping techniques,such as purge-and-trap technique,in which the resin is flash-heated and the compounds are desorbed at the same time to a cryogenic trap or an analytical column.In TPD,the adsorbent resin acts also as an analytical column.In this way it is possible to obtain more rapid analysis,and also a more simple instrumentation,which can be used on-line and on-site.In this work,a new version of TPD device,which uses a resistor for heating and a Peltier element for rapid cooling,was designed and constructed.Various adsorbent resins were tested for their adsorption and desorption properties of both polar and non-polar cortipounds.When using a mixture of adsorbent resins,Tenax TA and HayeSep D,it was possible to analyze both polar,low-molecular weight compounds,such as methanol and ethanol,and non-polar volatile organic compounds,such as benzene and toluene,in the same run within 15 min including sampling.The same TPD principle was also tested using a Fourier transform infrared spectrometer as an analytical instrument,and the results showed that it was possible to obtain a separation of similar compounds,such as hexane and heptane,and still retaining the same sensitivity as the original on-line FTIR instrument.