Mathematical modeling concentration regimes

It is useful to examine the consequences of a closed ion source on kinetics measurements. We approach this with a simple mathematical model from which it is possible to make quantitative estimates of the distortion of concentration-time curves due to the ion source residence time. The ion source pressure is normally low enough that flow through it is in the Knudsen regime where all collisions are with the walls, backmixing is complete, and the source can be treated as a continuous stirred tank reactor (CSTR). The isothermal mole balance with a first-order reaction occurring in the source can be written as... 

Figure 29-7 The predictive approach in kinetic methods. A mathematical model, shown as the blue squares, is used to fit the response, shown as the solid line, during the kinetic regime of a reaction. The model is then used to predict the equilibrium value of the signal, Ag, which is related to the analyte concentration. In the example shown, the absorbance is plotted vs. time and the early-time data is used to predict A, the equilibrium value, shown as the blue circle. (Reprinted with permission from G. L. Mieling and H. L. Pardue, Anal. Chem., 1978,50, 1611. Copyright 1978 American Chemical Society.)...

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