3-3) Channeling Caused by Bubbles Forming or Accumulating Inside Columns

Fig. 13Channeling Due to Bubbles Inside the Column

Bubbles tend not to occur inside columns because the increased pressures increase the saturated solubility for air. However, bubbles can tend to form in the relatively low-pressure area near the column outlet if heated by an oven. It is also possible for air bubbles to accumulate in such area after passing through the pump.
Such cases can cause the flow of mobile phase in the column to vary, resulting in peak distortion (Figure 13).

Note that the larger the column diameter, the more difficult it is for bubbles to pass out of the column. Therefore, if a preparative column is attached to the HPLC system, install the column so the inlet is as high as possible and the outlet as low as possible to minimize the bubbles having to overcome buoyancy.