Extra Column Dispersion - Dispersion in Detector Sensors Due to Newtonian Flow > Page 41

Dispersion in Detector Sensors Due to Newtonian Flow

The majority of sensor cells are cylindrical in shape, relatively short in length and have a small length-to-diameter ratio (small aspect ratio). Unfortunately, the small aspect ratio conflicts with the assumptions adopted by Golay in the development of the equation that describes the dispersion that takes place during fluid flow through an open tube. As a consequence, the Golay equation for open tubes can not be applied to cylindrical sensor cells. As a result, Atwood and Golay [12] extended the theory of dispersion in open tubes to tubes of small length-to-diameter ratios. Details of the development of the theory will not be given here because, with proper cell design, it is no longer pertinent to practical chromatography systems. It will be seen that, if the sensor cells are designed correctly, dispersion from Newtonian Flow can be made negligible. Nevertheless, the effect of the cell on solute profiles is shown in Figure 18.

J. Chromatogr. 186(1979)353

Figure 18. Elution Curves Presented as a Function of the Normalized Tube Length