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

Abstract

AbstractA 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%.