Condensed Phase Membrane Introduction Mass Spectrometry – Continuous, Direct and Online Measurements in Complex Samples

Direct mass spectrometric analysis of naphthenic acids and polycyclic aromatic hydrocarbons in waters impacted by diluted bitumen and conventional crude oil

“…To enhance sensitivity, CP-MIMS-LEI measurements were performed in stopped-flow mode (Duncan et al, 2011;Krogh and Gill, 2018;Vandergrift et al, 2020). To do so, a 6-port valve system was included directly upstream from the passive flow splitter.…”

“…The technique uses a semipermeable hollow fiber membrane (typically polydimethylsiloxane), which is directly immersed into a liquid or slurry sample. The membrane rejects ionized matrix components and particulate matter while allowing hydrophobic analytes to permeate through and dissolve into a flowing acceptor phase solvent (Krogh and Gill, 2018). The acceptor phase (typically methanol), containing the membrane-permeable fraction of the sample, is then infused into an appropriate ionization source, often electrospray or liquid electron ionization (Termopoli et al, 2019a;Vandergrift et al, 2020), to provide real-time results, which can be employed to provide both qualitative and quantitative data.…”

Direct Measurement of Acid Dissociation Constants of Trace Organic Compounds at Nanomolar Levels in Aqueous Solution by Condensed Phase–Membrane Introduction Mass Spectrometry

“…The technique employs a semipermeable membrane interface in direct contact with the sample. Molecules that permeate the membrane are transferred to the mass spectrometer as a mixture and analyzed in “real‐time.” A variant known as condensed phase (CP)–MIMS employs a solvent acceptor phase to transport permeating analytes to an atmospheric pressure ionization source of a mass spectrometer (Krogh and Gill ). A convenient configuration involves a polydimethylsiloxane (PDMS) capillary hollow fiber membrane (CHFM) mounted on an immersion probe that can be submersed into a sample.…”

Mass Spectrometry Based Approach for Organic Synthesis Monitoring

“…The membrane rejects particulate materials and is hydrophobic, with perm-selectivity characteristics favoring mass transfer of nonpolar analytes, rejecting highly polar and charged components, making MIMS ideally suited for the online extraction of neutral compounds from a complex reaction mixture. 17,18 There is some precedent in the literature for the use of MIMS for reaction monitoring utilizing electron ionization (EI). As a few examples, in early work, the Cooks group used a silicone membrane interface to transfer permeating analytes directly into a high vacuum EI triple quadrupole MS.…”

“…This approach has been termed condensed phase MIMS (CP-MIMS) and has been described in several reviews. 17,18 The use of CP-MIMS has allowed researchers to utilize a variety of MS ionization strategies, including ESI, atmospheric pressure chemical ionization (APCI) 23−28 and liquid electron ionization (LEI), 29−31 to extend the application of MIMS to larger, significantly less volatile analytes. In early work, Creaser and co-workers demonstrated the use of a CP-MIMS type interface system with a hydrophobic polyvinylidene fluoride microporous sheet membrane coupled with APCI to follow the course of a synthetic reaction, implemented by sampling reaction aliquots as a function of time.…”