Exitance nomenclature

For all the theoretical discussions in this book the Gaussian shape will be assumed, thus allowing us to draw some conclusions about the peaks and to use some standard nomenclature and symbols to describe chromatographic peaks. Remember that a peak represents the frequency distribution of all molecules of a particular analyte as they move as a group through the system or as they are detected as they exit from the system. The average molecule is found at the center of the distribution, at the position of the peak maximum, and it is this average position that is used to characterize the particular analyte. 

A brief mention of nomenclature is necessary here. First, note that the barrier at A is described as being in the entrance channel. This is merely a convenient name for an activation barrier in which the molecular bond length is nearly unchanged from its gas-phase value, (r — r ) By the same token, an exit channel barrier is one in which the molecular bond length is significantly stretched from its gas-phase value, (r — r " ) r . These are subjective criteria, useful mainly as limiting cases. Realistic PES will almost certainly fall in between each limit. 

We now translate the design into mathematics using the conservation of mass given in Eq. (3.9). We start with The total flow rate of stream 1 entering equals the total flow rate of stream 2 exiting plus the total flow rate of stream 3 exiting. With our nomenclature, this translates to... 

Rotational Couette flow (RCF) is analyzed in the next example. Because the flow is confined inside the Couette flow cell and there is no exit stream, we use the nomenclature G(y) and g(y)dy instead of F(y) mdj y)dy. 

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