Two other intrinsic characteristics of analytical microsystems have clear connections with technology developments: the extremely low sample volumes used,
and the presence of laminar flows. Small volumes of both sample and reagent (pl–nl
levels) are representative of most miniaturized systems. This characteristic has clear
advantages associated with cost and analytical throughput, but it also presents
disadvantages, such as the suitability of detection techniques. Consequently, much
research effort has been focused on the development of miniaturized and sensitive
detection units [7], and today the detection improvements are still one of the most
important research focuses [8]. As a consequence of the low volumes required,
a very precise handling of sample is crucial in microanalytical systems, and a high
dependence of the surface properties of microchannel manifolds and interconnections and dead volumes is observed [3]. Complex fluid manipulation at femtolitre
and nanolitre scales is readily achieved without any mechanical valves or external
pumps by using the electrokinetic phenomena [9]. In this way, the focus has been
centred on the integration of functional components within monolithic systems
using both lithography and micromoulding technologies. Micropumps are other
typical devices used to propel fluids in microchannels. A recent review has been
published by P. Woias [10]. A more sophisticated approach has been proposed by
M.S. Anderson [11], who presented a combined atomic force microscope (AFM)
and Raman spectrometer as a microfluidic device for sampling and trace chemical
In addition, analytical microsystems offer a significant decrease in costs, by
dramatically reducing the volume of samples and reagents needed to perform a
chemical analysis. This feature also opens up the possibility of processing
samples in parallel, which is very useful when the same chemical analysis must
be performed many times, as is the case in routine laboratories. This approach is
very useful when high-throughput screening is needed. In conventional analyses, handling and processing of the sample is frequently done manually, at least
in part, and often in specialized laboratories. However,mTAS allows chemical
analyses to be brought close to the place where they need to be performed,
independent of both the laboratory and the laboratory personnel. Thus, these
integrated analytical systems are very suitable for online measurements