MECHANICALLY ENHANCED CAPILLARY COLUMNS

Improved mechanical properties of silica capillary columns for chromat ography can be obtained by depositing a material with a coefficient of thermal expansion smaller than that of silica. This effect is obtaine d through the deposition of TiO2-doped silica with a negative thermal expansion coefficient by a traditional modified chemical vapor deposit ion method on the inside of the tube and by a high frequency, inductio n-coupled plasma torch process on the outside. The deposition is made inside and outside the silica tube, before drawing the column in a hig h temperature oven: thus, both inside and outside surfaces of the colu mn are placed under compression, reducing the propagation of surface f laws.