An integrated micro ion-exchange separator and detector on a silicon wafer

A miniaturized ion-exchange separator with integrated detection has been successfully fabricated using micro-electro-mechanical systems (MEMS) technology. The separator consists of a deep, micron-sized, open channel etched on a (110) silicon wafer. The surface of the channel was chemically activated for anion exchange with bonded-phase chemistry. Detection is through electrical conductivity measurement, with electrodes fabricated on the surface of the channel. Chromatographic performance of the device has been evaluated with ternary mixtures of bromide, chloride, nitrate, and sulfate ions, for the effects of sample size, mobile phase pH, co-ion type, and carrier velocity. It is shown that the performance demonstrates successful ion-exchange chromatography in the integrated separator/detector.