One of the oldest and most important challenges in analytical chemistry is the accurate measurement of a specific compound in a complex matrix. Generally, this can be carried out by following two main approaches: improving selectivity toward the detection system by using selective (bio)sensors or improving selectivity toward separation systems with nonspecific detectors coupled after the separation of sample mixture in distinct zones of single analytes. Miniaturization of the first approach was studied in Chapter 7, and the miniaturization of the second approach will be studied here.The micro total analysis system (mTAS) concept was developed from a modification of the total analysis system (TAS) approach by downsizing and integrating its multiple steps (injection, reaction, separation and detection) on to a single device, yielding a sensor-like system with a fast response time, low sample consumption, onsite operation and high stability [1,2]. The fact that miniaturized analysis systems contain all the elements needed to perform the required analysis is clearly reflected in the term 'mTAS'. The recent strong interest in this approach is stimulated by the fact that the attempt to find solutions for chemical measurement problems through development of individual sensors for each of the desired parameters has not been very successful up to now [3]. The main reason for this probably lies in the wide