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

A new micro total analysis system (mu TAS) designed for volumetric nanotitr ations, integrating two electroosmotically driven nanopumps and a sensor un it, is presented. The unique feature of the integrated electroosmotic pumps is their ability to pump widely different solutions, independent of intrin sic characteristics such as pH or ionic strength, with the exception of vis cosity. Typical flow rates achieved are in the range of 2-65 nl/s, dependin g on the number of microchannels connected in parallel and on the applied v oltage. The pulsation-free Rows developed in two nanopumps push out the sol utions contained in two reservoirs. The solutions are fed into a three-dime nsional mixer, where the chemical reaction takes place. The potential diffe rence as a function of the sample concentration is detected by means of a p seudo-reference electrode located in one channel and an indicator electrode placed downstream from the mixer in the sensor unit. (C) 2001 Elsevier Sci ence B.V. All rights reserved.