Analysis strategies miniaturization

One example of a miniaturized LC/MS strategy is the use of 96-well sample plates (Kaye et al., 1996) for extraction. This sample extraction procedure combines batch sample processing within a miniaturized format. Increased sensitivity and decreased volume advances have fostered a new wave of scale-down models. Experiments that were formerly performed at the bench are, instead, performed at the microliter scale in the batch mode. For example, synthetic process research was traditionally performed manually with apparatus at the milliliter level. This approach involves the testing of a range of synthetic conditions for optimum yield and minimum impurity production. Now, process research conditions are tested in microliter levels to produce information on purity and structure (Rourick et al., 1996). This strategy requires fewer reagents and accelerates the evaluation of a wider range of conditions in a shorter time. Another example includes the direct analysis of samples from cell culture experiments (Kerns et al., 1997). 

Even the lawn format still does not represent the final limit of miniaturization. The one well/one catalyst or one bead/one catalyst strategy, where catalyst identity is spatially coded, can be replaced by in situ synthesis combined with mass spectrometry [48]. The advantage of this strategy is the use of a mass spectrometer for the synthesis, reaction and analysis. The described electrospray ionization procedure helps to avoid the cleavage of chemical bonds, which would falsify the results. The synthesis step does not have to deliver clean and isolated products. Instead, after synthesis, the reactants are first separated by a quadrupole. In a second step, they are further reacted in an octapole and the reaction products are finally isolated in a second quadrupole and analyzed. Figure 3.15 describes the screening process in detail [49],... 

Another alternative technique, solid-phase microextraction (SPME), was used for the determination of fluoxetine [79] and several TCAs [80], SPME is a miniaturized and solvent-free technique, where analytes are extracted from the sample by adsorption on a thin polymer coating fixed to the solid surface of a fiber, located inside an injection needle or a capillary. Its main disadvantage is that special strategies are needed to couple SPME to the LC-MS analysis. 

Low detection limits of 10/xgl were established. Similar approaches for the miniaturization of SPR can be found in literature, however, similar to the miniaturized cantilever biosensor, any surface-active interfering compound in samples will cause significant analytical challenges. Borchers and coworkers used a microchip evanescent waveguide for the detection of realtime DNA hybridization events. A lower detection limit of 0.21 nmol 1 was demonstrated. The authors also showed multi-analyte detection capabilities of their system and suggested that this strategy can be utilized in real-time DNA array format with analysis times as short as 2 min. 

Perhaps the area of analysis in which electrochemistry has had the biggest impact on society is in biosensors, notably the glucose biosensor [48], Although Volume 9 is concerned with bioelectrochemistry, it is important that this area of electroanalytical chemistry is represented appropriately in Volume 3. Consequently, Schuhmann and Bonsen provide an overview of the physical principles and appKcations of biosensors in Chapter 2.11. A comprehensive overview is given of amperometric, potentiometric, conducti-metric and impedimetric formats for biosensors, and the relative merits of each are fully assessed. Potential new directions are highlighted, particularly connected to miniaturization and multisensor array detection strategies. 

In conclusion, despite the simplicity of the sustainability criterion retained, the analysis shows how multi-scale design enables various aspects of process miniaturization and intensification to be reconciled. By including a new design parameter, this strategy makes it possible to reconcile the rapid transfer characteristics offered by... 

Reaction and Process System Analysis, Miniaturization and Intensification Strategies... 

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