Exploring the pressure resistance limits of monolithic silica capillary columns

• A cyclic approach is proposed to test the pressure stability limits of silica monolith capillaries.
• Two domain sizes and two inner diameter cases were considered for testing.
• Silica monolith capillary columns can at least withstand pressures up to 80 MPa.
• No noticeable effect on the chromatographic performance was observed.

We report on an experimental approach to measure the pressure stability and mechanical strength of monolithic silica capillary columns with different diameters (50 and 100 μm i.d.) and considering two different domain sizes, typical for the second generation monoliths or smaller. The approach consists of exposing the capillaries to ultra-high pressures (gradually stepwise increased from 20 to 80 MPa), with intermediate measurements of the column efficiency, permeability and retention factors to check the mechanical stability of the bed. It was observed that all tested columns withstood the imposed pressure stress, i.e., all the tested parameters remained unaffected up till the maximal test pressure of 80 MPa. The applied pressure gradient corresponded to 320 MPa/m. The two 100 μm i.d.-capillary columns were also exposed to pressures between 80 and 90 MPa for a prolonged time (8 h), and this did not cause any damage either.