Liquid chromatography on-chip: progression towards a mu-total analysis system

After a brief introduction to the area of miniaturised analytical separatio n systems, this paper details the fabrication of components for a miniaturi sed liquid chromatography system. To date, inlet and outlet connection port s, separation mu-channels (20-200 mu m in width, 0.5-10 mu m in depth, 15-5 0 cm in length), and an intersection for picolitre injection have been etch ed on a silicon wafer and then sealed with a Pyrex cover plate on which pla tinum electrodes for on-chip detection have been machined. In addition the mu-channel walls have been chemically modified with n-octyltriethoxysilane and the reverse phase retention of the drug caffeine was observed using off -chip injection (20 nl) and UV detection (3 nl flow cell). The on-chip plat inum electrodes have been used for the amperometric detection of phenol. In addition, using external valving, initial results indicated a successful m ode for a partially integrated on-chip injector which should allow further progression towards a mu-chromatographic analysis system.