Silver-cemented frit formation for the stabilization of the packing structure in the microchannel of electrochromatographic microchips

A simple but effective frit formation technique was developed to stabilize the packing structure inside the microchannel of capillary electrochromatographic microchips, utilizing the electroless plating technique. A Ag(NH3)2+ solution was allowed to diffuse through the colloidal silica packing in the microchannel from the reservoir of the microchip for a limited amount of time, and then it was reduced by an excess amount of formaldehyde solution. A frit structure of ∼70 μm in length was formed at the entrance of the microchannel without clogging when treated with 1 mM Ag(NH3)2+ ion and formaldehyde for 30 s and 150 s, respectively. The formation of the frit structure was confirmed by a scanning electron microscopy. The stability of the packing structure was tested rigorously and then confirmed by applying alternating electroosmotic flows back and forth with pulsed potential steps on both sides of the frit structure. The effect of the treatment on the electrochromatograms was evaluated after the microchips were repeatedly used and stored for a long period of time. The results indicated that the silver-cemented frit structure extended the lifetime of the fully packed CEC microchips distinctly.