Silanization of glass in the making of ion-sensitive microelectrodes

The silanization of glass, particularly Pyrex, was studied using reaction conditions that might be applied in the fabrication of ion-sensitive microelectrodes of the liquid-membrane type. The efficacy was tested by measuring the hydrophobicity (contact angle) or electrical resistivity of the treated surface. Aminosilanes, such as trimethyl-(dimethylamino)-silane are better than chlorosilanes, the optimum temperature is 250-330 degrees C, and the reaction comes near to completion in 5 min. Silanization of glass that is newly exposed (as in the pulling of a micropipette) is greatly improved if the surface is treated with acid. There is considerable variation from one kind of glass to another. A recipe for making double-barrelled ion-sensitive microelectrodes is given.