Partial electroosmotic pumping in complex capillary systems: Part 2: Fabrication and application of a micro total analysis system (μTAS) suited for continuous volumetric nanotitrations

A new micro total analysis system (μTAS) designed for volumetric nanotitrations, integrating two electroosmotically driven nanopumps and a sensor unit, is presented. The unique feature of the integrated electroosmotic pumps is their ability to pump widely different solutions, independent of intrinsic characteristics such as pH or ionic strength, with the exception of viscosity. Typical flow rates achieved are in the range of 2–65 nl/s, depending on the number of microchannels connected in parallel and on the applied voltage. The pulsation-free flows developed in two nanopumps push out the solutions contained in two reservoirs. The solutions are fed into a three-dimensional mixer, where the chemical reaction takes place. The potential difference as a function of the sample concentration is detected by means of a pseudo-reference electrode located in one channel and an indicator electrode placed downstream from the mixer in the sensor unit.