A fully integrated trap‐membrane inlet mass spectrometry system for the measurement of semivolatile organic compounds in aqueous solution

Abstract

A novel procedure to perform a membrane-inlet mass spectrometry experiment is presented, which allows semi-volatile organic compounds to be preconcentrated inside the membrane, before they are thermally released into the ion source. The method uses a standard membrane inlet with a tubular silicone membrane passing straight through the ion source of the mass spectrometer. A long slit in the ion source parallel to the membrane allows electrons from the filament to continuously bombard the membrane surface. The membrane is kept cold by a continuous flow of water or sample solution passing through the inlet. However, during a short interruption of the flow, the membrane is rapidly heated by the electron bombardment and organic compounds dissolved in the membrane are thermally released into the ion source. In this fashion a desorption peak is obtained. Using the areas of the desorption peaks, we have been able to detect semi-volatile, hydrophobic organic compounds (boiling points above 200 "C) in aqueous solution at low and sub parts-per-billion levels. In general, the detection limits were 10-100 times lower than previously published results, where membrane-inlet mass spectrometry has been used for the detection of the same compounds. Good linearity over 3 orders of magnitude was obtained and the standard deviation was 5%.

Improving the selectivity of non-polar alkanes, alkenes, and aromatic hydrocarbon compounds by the application of acetonitrile as a Cl reagent

“…Considering the proposed CI reagent produces high detection limits for the test compounds, it is believed that coupling CH 3 CN CI with a preconcentration step [7,[25][26][27][28] or with a mathematical based multicomponent quantitation method such as a nonlinear asymmetric error function-based least mean square method (NALMS), which can identify and quantify individual compounds in sample mixtures based on the ability of computer generated software to analyze and separate complex multicomponent EI spectra into the individual constituents, could be useful in increasing the selectivity of MIMS when measuring non-polar hydrocarbons in air samples.…”

Real-Time Broad Spectrum Characterization of Waste by Membrane Introduction Mass Spectrometry

“…These effects might be eliminated by appropriate heating of the membrane material, using electron beams [11], lasers, or pulsed radiant heaters to reduce response times. Alternative membranes may also provide an efficient and reliable interface for SVOC introduction.…”

Development of Multi-Membrane Near-Infrared Diode Mass Spectrometer for Field Analysis of Aromatic Hydrocarbons

“…Materials beyond PDMS, such as those with nanocrystallines, are of further interest. Thermal methods have increased the temperature of the membrane inlet with increased analyte perviousness increasing resolution [25,26]. Developed CO 2 laser desorption methods have augmented the analyte release from the membrane on the vacuum side of instrumentation [27].…”