Why do porous polymer PLOT columns bleed more than Liquid phases?

Sometimes we get customer reaction that porous polymer PLOT columns bleed a lot. They are used to the low bleed values using Rxi-series of columns and wonder why this is not the case with porous polymers. Porous polymer columns have a huge amount of stationary phase to generate sufficient loadability and retention. Typically porous layers are upto 20 um in thickness, That means for a 30m column, a porous polymer PLOT has approx. 200 x more stationary phase compared with a 30/0.25/0.25 type Rxi column.

Therefore much higher bleed values can be expected for the porous polymer type columns. If we aim for same bleed as Rxi, we must realize, the upper temperature should be listed 100C lower.

The max temp. listed for porous polymer columns is kept high, to be able to bake-out impurities that may accumulate on the column. The new generation Rt-Q-BOND columns do offer a lower bleed while films are thicker, reducing background but with higher capacity so technology is improving.

Further reading:    http://www.restek.com/Technical-Resources/Technical-Library/Petroleum-Petrochemical/Restek-s-PLOT-Column-Family-PCSS1163G-UNV



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