Detection of Siloxanes in Landfill Gas and Biogas Using SIFT-MS

Increasing amounts of anthropogenic siloxane compounds are finding their way into landfills. The growing concentrations of siloxanes in landfill gas presents problems to the landfill and digester plant operators who seek to utilize methane production from the landfill or digester gas as an energy source. Results are presented for monitoring the reactions of SIFT-MS reagent ions H3O+, NO+ and O-2(+) with a number of the siloxanes, including hexamethyldisiloxane, C6H18OSi2, trimethylsilanol, C3H10OSi, octamethyltrisiloxane, C8H24O2Si3 and hexamethylcyclotrisiloxane, C6H18O3Si3. Collision rate reactions were assumed for the H3O+ ion and close to collision rate were found for the other two reagent ions. These results were then utilized to monitor siloxanes produced at three landfill sites. The SIFT-MS method was found to be simple to use, and fast without the need for sample pre-concentration.