Abstract:The benefits of on-site analysis of environmental pollutants are well known, with such techniques increasing sample throughput and reducing the overall cost of pollution level monitoring. This article describes a transportable time-of-flight (TOF) mass spectrometer, based upon a converging, annular TOF (CAT) arrangement. The instrument, the transportable CAT or T-CAT is battery powered and self-contained. The vacuum chamber is never vented and is kept at a very low pressure, even during analysis. Sample gases … Show more
“…These experiments are often performed by using ion trap mass spectrometers . In a study that uses a ®eld-portable TOF mass spectrometer, a simple membrane inlet has been developed for the on-site analysis of environmental pollutants (White et al, 1998). The reported detection limits were 2.1 ppb, 2.3 ppb, and 3 ppb for benzene, toluene, and xylene, respectively.…”
Section: E Mass Analyzers Commonly Used With Mimsmentioning
“…These experiments are often performed by using ion trap mass spectrometers . In a study that uses a ®eld-portable TOF mass spectrometer, a simple membrane inlet has been developed for the on-site analysis of environmental pollutants (White et al, 1998). The reported detection limits were 2.1 ppb, 2.3 ppb, and 3 ppb for benzene, toluene, and xylene, respectively.…”
Section: E Mass Analyzers Commonly Used With Mimsmentioning
“…22 Utilization of the PLS algorithm for mixture analysis was also recently reported in conjunction with a portable time-of-flight membrane inlet mass spectrometer. 23 In our group a nonlinear asymmetric error function-based least mean square (NALMS) approach for qualitative and quantitative determination of individual compounds based on the multicomponent mass spectra measured by MIMS has been developed. 24,25 This approach is a modification of the general deconvolution method, which assumes that the intensity of any mass-to-charge ratio (m/z) is a linear function of the concentration of the chemical compounds contributing to that particular m/z.…”
A nonlinear asymmetric error function-based least mean square method (NALMS) for the deconvolution of identity and quantity of individual compounds based on the multicomponent mass spectra measured by membrane inlet mass spectrometry (MIMS) was developed and detailed testing results are presented. The method utilizes the complete mass spectra of the compounds present in a reference library during the calculation of a solution for an unknown multicomponent mass spectrum. The results presented here and in our previous publications in which the NALMS method was utilized show that the method can be used to separate complex multicomponent electron ionization mass spectra into their individual constituents, thus considerably improving the selectivity of MIMS.
“…During the past few decades, other advancements in volatile compound and gas analysis with the MIMS technique include the development of portable time-offlight mass spectrometers for environmental analysis [11]. The viability of environmental atmospheric monitoring using MIMS sampling has also been examined [3,12].…”
Abstract. Membrane Inlet Mass Spectrometry (MIMS) is a technique that incorporates a semi-permeable membrane selective for differing organic molecules and chemistries. This eliminates the need for time-consuming sample preparation and facilitates near instantaneous analysis. This study will examine how the front end of MIMS incorporates three dual inlet ports, allowing for differing MIMS materials and selectivity for specific environments. Polydimethylsiloxane (PDMS) membranes have proven to be selective of benzene, toluene, and xylene (BTX) as well as aromatic hydrocarbons that are common in petroleum products while remaining selective against the aliphatic chains. PDMS has proven to be a successful choice of membrane with high permeability in atmospheric environments. In addition, polycyclic aromatic hydrocarbons (PAHs) such as acenaphthene, acenapthylene, naphthalene, and fluorene have recently been detected to the 5 ppb level in a nitrogen atmosphere with our current configuration. This preliminary work provides proof of concept using near-infrared laser diodes that act upon the membrane to increase its permeability and provide higher sensitivity of aromatic samples.
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