Preparation of glass capillary columns coated with immobilized OV‐240‐OH (33% cyanopropyl substituted, OH‐terminated). An approach to improve the inertness and thermal stability of cyanoalkyl polysiloxane coatings

Coating intensely leached glass capillaries with OV‐240‐OH, the most polar commercially available OH‐terminated polysiloxane phase at the present time, is described. Beside chemical bonding of the phase via condensation with silanol groups of the support, additional immobilization using dimethyltetramethoxysiloxane as a crosslinker is carried out. After in situ methylation of the immobilized coating, and transformation of acidic impurities of the cyanopropyl substituted phase into the respective methyl esters, increased inertness of the column was observed. Working instructions are given, and processes involved are discussed.