The application and development of membrane -introduction mass spectrometry for the rapid and selective monitoring of chemical systems
Abstract
Membrane introduction mass spectrometry (MIMS) is an emerging on-line monitoring tool for quantifying and identifying trace environmental contaminants and industrial reaction by-products (e.g. CNCl, epichlorohydrin, EtOH). Membrane inlets, typically composed of silicones, are the only barrier between the vacuum of the mass spectrometer and gaseous or liquid sample streams. Method sensitivity is dependent on the selective partitioning of analytes from their respective matrix, and relies on membrane solubility and the boiling point of the analyte. MIMS is ideally suited for monitoring turbid bioreactors (>15% solid), which has been reported with an instrumental system packaged to operate under pilot plant conditions (NREL, Golden, CO). A representative sample from a 9000-liter ethanol fermentation reactor was taken continuously using a stainless steel tangential filter as the only sample pretreatment. After one week of off-line operation in the pilot plant, on-line monitoring was continued for a period of four days, producing data in quantitative agreement with off line HPLC experiments. New membrane technologies, based on low vapor pressure liquids, have been developed to increase method flexibility and provide a mechanism for selectively monitoring complex mixtures. Polyphenyl ether, alkylated cyclopentane, perfluorinated ether and silicone oil have been evaluated for the universal monitoring of aqueous solutions, and offer flexibility of size and chemical composition. Polyphenyl ether was subsequently admixed with 10% octadecylamine (wt/wt) to create an affinity-liquid membrane which utilized Schiff base chemistry to selectively bind and release aryl aldehydes. Further research involving the acid-catalyzed ring opening of epichlorohydrin, instrumental development, and tandem mass spectrometry techniques are also presented in the context of developing new membrane technologies.
Degree
Ph.D.
Advisors
Cooks, Purdue University.
Subject Area
Analytical chemistry|Chemical engineering
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