Real-Time Analysis of Methanol in Air and Water by Membrane Introduction Mass Spectrometry

Abstract

We present results for the near-real-time, on-line detection of methanol in both air and water using membrane introduction mass spectrometry (MIMS). In these experiments, we compare the sensitivity of a poly(dimethylsiloxane) (PDMS) membrane and an allyl alcohol (AA) membrane to the detection of methanol. In MIMS, the membrane serves as the interface between the sample and the vacuum of the mass spectrometer. Membrane-diffused water was used as the reagent ion (H3O+) for chemical ionization of methanol in an ion trap mass spectrometer. Linear calibration curves have been obtained for methanol using both PDMS and AA membranes. For PDMS, detection limits of methanol are 14 ppmv and 5 ppm in air and water, respectively. For AA, detection limits are 3.3 ppmv and 2 ppm in air and water, respectively. We demonstrate that the sensitivity of the analysis can be altered by the chemistry of the membrane. When the AA membrane is used, the sensitivity of MIMS is enhanced over that of PDMS by a factor of 8.5 for methanol in air and by a factor of 23.4 for methanol in water.

Characterization of a Membrane Interface for Analysis of Air Samples Using Time-of-flight Mass Spectrometry

“…Time-of-flight mass spectrometry (TOFMS) differs fundamentally from mass spectrometry techniques that use scanning instruments, such as quadrupole, [12][13][14] ion trap, [15][16][17] and magnetic sector 18 analyzers, in that the formation of discrete ions and the mass dispersion is accomplished in the time domain rather along a spatial axis. Because a complete spectrum is generated in each cycle, the relative intensities of ions in the source are accurately represented, even if source conditions change during the experiment.…”

Chloroform formation by chlorination of aqueous algae suspensions: online monitoring via membrane introduction mass spectrometry

“…[12][13][14][15][16][17][18] In this technique volatile and semi-volatile organic compounds permeate hydrophobic membranes, usually polydimethylsiloxanes (PDMS), preferentially to water and other polar substances. MIMS can be applied to real-time and in-situ monitoring of chemical processes, such as: (a) conversion of chlorine to chloramines, an environmentally relevant reaction; [19][20][21] (b) chlorination of phenol and related compounds, models of humic substances by sodium hypochloride; 22 (c) oxidation of benzene derivative by the Fenton's reagent; 23 (d) photolysis of aryl methyl ester in aqueous and aqueousmethanolic solutions; 24 (e) hydrolysis of epichlorohydrin, a significant compound in the polymer industry; 25 and (f) catalytic hydrodechlorination of aromatic chlorides, an important process to treat organochloro compounds.…”

Membrane introduction mass spectrometry applied to the monitoring of chloroform degradation by hypochloride in acidic aqueous medium

“…[7][8][9][10][11][12][13] In this technique volatile and semivolatile organic compounds permeate hydrophobic membranes, usually polydimethylsiloxanes (PDMS), preferentially to water and other polar substances. [14][15][16] MIMS can be applied to real-time and in-situ monitoring 14,[16][17][18] of chemical processes, such as: (a) conversion of chlorine to chloramines, an environmentally relevant reaction; [19][20][21] (b) chlorination of phenol and related compounds, models of humic substances, by sodium hypochloride; 22 (c) oxidation of benzene derivatives by Fenton's reagent; 23 (d) photolysis of aryl methyl ester in aqueous and aqueous-methanolic solutions; 24 (e) hydrolysis of epichlorohydrin, a significant compound in the polymer industry; 25 (f) catalytic hydrodechlorination of aromatic chlorides, an important process to treat organochloro compounds.…”