A field portable membrane introduction mass spectrometer with in-line standard infusion and sample heat exchanger for real-time monitoring of volatile organic compounds in aqueous samples

Maintaining a steady sample temperature when analyzing real-time samples in the field is crucial for Membrane Introduction Mass Spectrometry (MIMS). Diffusion through the membrane interface is temperature dependent, and sample temperature might vary depending on the sample source. In order to reduce this source of inaccuracy, an in-field and online continuous monitoring system based on (MIMS) coupled with a heat exchanger and in-line standard addition was developed for monitoring volatile organic compounds (VOC) in actual field samples. Parametric studies of the heat exchanger have been conducted in the laboratory. In order to maintain control on instrumental signal drift during continuous, long-term analysis periods, the system used continuous infusion of internal standard (tuloene-d8) into the sample stream and also provided the possibility to infuse, in the same way, an analyte for standard addition calibration. This set-up has been utilized in the field for analyzing both natural water sources and heavily polluted process water. The system was demonstrated to offer a rapid method for quantifying volatile hazardous pollutants in aqueous matrices with good time-resolution.