Bioanalytical applications separation techniques

The first field of application for SdFFF were latex beads, which were used either to test the channels or to produce separation results alternative to other separation techniques. PS nanoparticles used as model surfaces for bioanalytical work have been analyzed by SdFFF [39]. The appealing feature of SdFFF is its ability to characterize particle adlayers—by direct determination of the mass increase performed by observing the differences in retention between the bare and coated particles—with high precision and few error sources the mass of the coating is determined advantageously on a per particle basis. 

Sample collection and preparation are crucial issues for any bioanalytical application in order to address the complexity of samples originating from biological tissues and fluids. It is necessary to cope with the lack in concentration sensitivity typical for capillary separation techniques, to avoid interference from matrix components as well as to ensure analyte stability. In peptide analysis, a strong focus exists on handling small-volume samples and on selective concentration of the analyte in order to overcome limitations with respect to loadability. In addition, loss of analyte frequently occurs due to degradation by proteases and due to adsorption to surfaces, which accordingly needs to be minimized. 

Mass spectrometry (MS) is one of the most powerful detection techniques used in liquid-phase analyses,1 mainly due to the ease of interfacing with separation techniques such as capillary electrophoresis (CE)2,3 and high-performance liquid chromatography (HPLC).4 Due to its sensitivity and applicability to a wide variety of chemical and biochemical species, MS is also used for the analysis of (bio)chemical molecules processed in microfluidics devices.5,6 Electrospray ionization (ESI)7 10 is often used to transfer samples from microfluidics chips to a mass spectrometer, involving analyte ionization directly from solutions and operating at flow rates typically used in microfluidics devices.11 Due to its effectiveness, the use of chip-MS coupling has rapidly spread in many research areas with bioanalytical applications,12 such as the... 

Due to the rapidly growing importance of capillary columns in bioanalytical applications, special attention will now be devoted to sampling techniques associated with capillary GC. Small samples are typical for this type of chromatography and, consequently, a direct introduction of such samples is an apparent technological problem. In most biochemically interesting applications (typically, trace analysis problems), there is no general discrepancy between the demands of such analysis and the performance and sensitivity of capillary separation techniques. However, the manipulation of samples presents difficulties, as reliable methods for measurement, disposal, and introduction of nanoliter volumes are not readily available. Ironically, in many capillary GC applications, the solvent serves only as a sample vehicle we... 

Optofluidics Applications, Table 1 Comparison of bioanalytical separation techniques ... 

Having been an important analytical technique since the first detailed studies in the mid-1960s, ECL will continue to have a promising future in analytical and bioanalytical science. The ECL of Ru(bpy) " and its derivatives will be further investigated to expand the range of its applications, especially in the area of diagnostic testing and immunoassay. ECL coupled with separation techniques should still be attractive for analysts. The need for low-cost, portable analytical instruments in the areas of environmental anal-... 

Though we and others (27-29) have demonstrated the utility and the improved sensitivity of the peroxyoxalate chemiluminescence method for analyte detection in RP-HPLC separations for appropriate substrates, a substantial area for Improvement and refinement of the technique remains. We have shown that the reactions of hydrogen peroxide and oxalate esters yield a very complex array of reactive intermediates, some of which activate the fluorophor to its fluorescent state. The mechanism for the ester reaction as well as the process for conversion of the chemical potential energy into electronic (excited state) energy remain to be detailed. Finally, the refinement of the technique for routine application of this sensitive method, including the optimization of the effi-ciencies for each of the contributing factors, is currently a major effort in the Center for Bioanalytical Research. 

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