Resolution and Detectability

FIGURE 1.1 (a) Positive and (b) negative feedback effects on a disk-shaped tip from a sub- 

The detectability of SECM is much higher for an electroactive spot with a high aspect ratio as demonstrated by using a nanoband electrode as a model substrate [21-23]. 

For instance, ultra long single-walled carbon nanotubes with a diameter of only -1.6 nm were grown on the Si02-coated Si wafer to detect individual nanotubes by using 1.5- to 10-pm-diameter SECM tips in the feedback mode [24]. This superb detectability is ascribed to the efficient nanoscale mass transport of a redox mediator at the nanotubes. In addition, the nanotubes were much longer than the tip diameter to give a substantial feedback response at steady states under unbiased conditions. 

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It is interesting to note the analogy of developments in light microscopy during the last few decades. The confocal microscope as a scaiming beam microscope exceeds by far the nomial fluorescence light microscope in resolution and detection level. Very recent advances in evanescent wave and interference microscopy seem to promise to provide even higher resolution (B1.18). 

Spatial Resolution and Detection Limits of Analytical STEM 167... 

Intermediate isothermal temperatures may result in part of the chromatogram having acceptable resolution and detection limits whilst other parts do not. 

When acetonitrile/methanol was used as the mobile phase, the concentration of methanol had to be increased to 50% before the TGs could be eluted in a reasonable length of time when ethanol was used as the polar organic modifier with ACN, resolution and detection were improved and only 20% ethanol was required. 

FIGURE 6.21 Comparison of resolution and detection sensitivity of ITPZE and ZE separations. Sample, dsDNA ( )X I lAHlae in 0.1 x PCR buffer. The ZE sample has a 25x higher total DNA concentration than the ITPZE sample. The average signal enhancement from ITP is 40-fold [636]. Reprinted with permission from Wiley-VCH Verlag. 

The aspects considered for a reliable evaluation of the performance of the miniaturized mass spectrometer are repeatability, resolution, and detection limit. Over the last years, these parameters could be improved by theoretical analyses and validated with successive chip generations [34, 35],... 

More protein sequences will be deduced from DNA sequences in the future. However, the sequencer utilizing the principle of Edman degradation wil continue to be an important tool. Sensitivity should be enhanced with further development of fluorescent reagents. As enormous improvement has made in recent years, mass spectrometry is quite promising for its role in sequence determination. Two-dimensional polyacrylamide gel electrophoresis and capillary electrophoresis show excellent resolution and detection sensitivity. 

Many studies on plants that contain ellagitannins also report numerous unidentified or poorly characterized ellagitannins often in the form of poor peak resolution and detection of isomers that share a common... 

In many countries undertaking the most technically demanding analyses, it is expected that the laboratories will be registered under quality assurance schemes. Accuracy and repeatability should be covered by quality assurance requirements, but resolution and detection limits are critically dependent on technique and instrumentation. Details on the general subjects of quality assurance/quality control, quantification of uncertainty in analytical measurements, accreditation of laboratories, and on the general concepts and strategy for ensuring that analytical chemical measurements are comparable - in one word traceability - can be found elsewhere in the chemical literature (26,32-36). 

I 7 7 Raman Spectral Imaging on Pharmaceutical Products 11.2.3.3 Spectral Resolution and Detection Limit... 

Figure 3b. Improved peak resolution and detection by using 13%...

Multiple development was traditionally performed manually. It consists of repeated developments of a plate in the same direction with the same solvent over the same distance. The result is narrower bands and improved resolution and detection sensitivity. The Rf values become very precise and are adequate enough for identification. A variation of this method is automated multiple development (AMD) and shows promising future. The HPTLC/AMD method was used to monitor phenylureas, carbamates and triazines in drinking water. HPTLC can also be performed using polar modified stationary phases to separate pesticides in various foodstuffs such as triazines in corn, asparagus, tomatoes, grapes and potatoes [14]. 

In another example, if the goal is to locate neuronal cell bodies containing a specific neurotransmitter, a high detection sensitivity and low detection resolution method would allow the label to diffuse throughout the entire cell. Then the location of specific neurotransmitter molecules within the cell is not important rather location of a cell that contains neurotransmitter is important. The bottom line is to assess the importance of detection resolution and detection sensitivity in selecting a detection method. 

A detailed discussion of the different possibilities for increasing the counting rate and finding a compromise between energy resolution and detection limits is, of course, outside the scope of this review. 

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