Method for quantification of chemicals in a pollution plume using a moving membrane-based sensor exemplified by mass spectrometry.

Quantification of a chemical concentration in a pollution plume using a moving membrane-based sensor can be problematic. In many cases, the sensor passes through the plume faster than the time necessary to reach a steady-state signal, which is often used for quantification. Since the exposure time is typically not known, quantification based upon the flow injection analysis principle is also impractical. In this paper, we present a two-dimensional calibration model, exemplified by membrane inlet mass spectrometry, in which the concentration of a chemical can be determined using a simple algorithm. The concentration is given by a calibration factor, which is multiplied by the peak height and divided by the value of a polynomial, calculated at a normalized peak width. The model is demonstrated to give good quantitative estimates of concentrations for exposure times down to approximately 1/10 of the time it takes to reach steady-state diffusion through the membrane. Although the model is demonstrated using membrane inlet mass spectrometry and detection of volatile organic chemicals, it should be generally applicable to many membrane-covered sensors.