Development of multi-membrane near-infrared diode mass spectrometer for field analysis of aromatic hydrocarbons.

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.