Dynamic Range - Dilution

The version 2.0 assay uses a different set of probes designed to hybridize to genotypes 1 to 6 with equal efficacy (Fig. 4). The new probe set not only enhanced the efficiency of binding to genotypic variants but also lowered the LOQ from 3.5 X 105 to 2 X 105 HCV RNA equivalents/ml (Detmer et al., 1996). The version 2.0 assay displayed almost a 600-fold dynamic range up to 1.2 X 108 RNA equivalents/ml. The LOQ was set at 2 X 105 to ensure a specificity of 95%. The assay was reproducible, with a mean CV of 14% for replicates of low-, middle-, and high-titer sera. Serial dilutions of quality level 1 RNA transcripts (Collins et al,... 

The dynamic range of UV detectors for CE can be more limited than for EC. Einearity should therefore always be tested for the main component as well as the impurities. A general solution when the main peak is off-range is to inject a diluted solution to determine the response for the main component and a concentrated solution for the impurities. Alternatively, a small and a large injected volume of the same solution can be compared. In both cases, an internal standard is needed to be able to compare the two injections. 

Figure 14.7—Characteristics of a hollow cathode lamp (element As). Because the dynamic range in atomic absorption is narrow (two decades), the choice of a second wavelength of weaker absorption avoids the need to dilute a solution when an element is present in high concentration.

The dynamic range of OSME and GC-SNIFF data is generally less than a factor of ten, whereas dilution analysis frequently yields data that cover three or four powers of ten. It has been determined, however, that compressive transforms (log, root 0.5, and so on) of dilution analysis data are needed to produce statistics with normally distributed error (Acree and Barnard, 1994). Odor Spectrum Values (OSVs) were designed to transform dilution analysis data, odor units, or any potency data into normalized values that are comparable from study to study and are appropriate for normal statistics. The OSV is determined from the equation ... 

The calibration of atomic spectrometers can be handled much easier than that of conventional IC detectors using the large dynamic range of ICP techniques. Those simple off-line calibrations had been used for ICP-AES and ICP-MS in on-line preconcentration applications. With its ability to decide between isotopes the ICP-MS is well suited for isotope dilution analysis (IDMS), a calibration tool which increases the accuracy, the results and saves time due to reduced calibration work. The use of IDMS in combination with on-line coupling methods allows a significant speedup of the usually to IDMS applied time consuming separation processes. 

The width of the linear dynamic range determines the magnitude of dilutions needed for accurate sample analysis and affects each analyte s PQL. 

The laboratories maximize their sample throughput by reducing the number of samples that need reanalysis due to dilution. To reach this end, they routinely calibrate all of the instruments using the widest possible calibration range that spans the full linear dynamic range of the detector. 

In order to calculate the CCD camera linear dynamic range of the photon emission, the average measurements of each dilution are plotted against the logarithm of the corresponding amount of recombinant luciferase. 

The limit of detection, limit of quantitation, and linear dynamic range are to be determined by serial dilution of a sample. Three replicate measurements at each level are recommended, and the acceptance criterion for calibration linearity should be a prespecilied correlation coefficient (say, an r2 value of 0.995 or greater). 

Serial dilution was achieved in a PDMS microchannel network for immunoassay, as shown in Figure 10.10. Immunoassay of IgG antibodies present in HIV+ human serum was conducted. Using 1 1 dilution ratio and 10 sequential dilutions (only three are shown in Figure 10.10), a dynamic range of 210 or 1000 of the serum concentration was obtained. The HIV antigens (gp41, gpl20) were first adsorbed on a PC membrane, which was then sealed by the PDMS... 

The expressions for the stress tensor together with the equations for the moments considered as additional variables, the continuity equation, and the equation of motion constitute the basis of the dynamics of dilute polymer solutions. This system of equations may be used to investigate the flow of dilute solutions in various experimental situations. Certain simple cases were examined in order to demonstrate applicability of the expressions obtained to dilute solutions, to indicate the range of their applicability, and to specify the expressions for quantities which were introduced previously as phenomenological constants. 

Flexibility. An instrument which can analyze a sample only for a fixed combination of elements is useful for routine analyses, such as clinical analyses, but becomes useless if the combination of elements is to be varied. The ideal multielement spectroscopic system would be able to determine any combination of elements desired, if those elements are amenable to analysis by spectroscopic techniques. Since real samples contain various elements in differing relative concentrations, it is necessary that an ideal multielement spectrometer be able to accept such samples without the need for varying dilutions to accomodate all elements present. Thus the instrument should have a wide dynamic range and be capable of adjustment so that different elements present in major, minor, and trace quantities in the same sample can be simultaneously monitored. 

Deposition of sample on the sampler, skimmer, ion optics, and other parts of the interface can lead to elevated blank levels as well as drift. This, in combination with the space-charge-induced chemical matrix effects, often requires further dilution of samples than is desirable. This can also limit the range of concentrations that can be measured for a set of samples even though the dynamic range may in theory be sufficient. An improved understanding of the chemical and physical characteristics of the deposition process and means to minimize them is needed. 

Biosensors are being increasingly used as detectors in FIA systems [284,285, 322, 379, 476]. The drawbacks of biosensors as direct in situ sensors, namely their low dynamic range, their lack of ability to survive sterilization, their limited lifetime, etc. are no longer valid ex situ because the analyzer interfaces the biosensor which can be changed at any time and FIA can provide samples in optimal dilution. The need for chemicals and reagents can be drastically reduced when employing biosensors, specifically when the entire system is miniaturized [48]. 

As regards AAS, one limiting factor is the dynamic range. For flame applications this can be extended by the use of automatic dilutors, which dilute samples to the useful range, thereby avoiding tedious and time-consuming manual dilutions. This is already in practical use, but even more sophisticated approaches can be foreseen in the near future. 

I. L. Garcia, P. Vinas, N. Campillo, M. H. Cordoba, Extending the dynamic range of flame atomic absorption spectrometry a comparison of procedures for the determination of several elements in milk and mineral waters using online dilution, Fresenius J. Anal. Chem., 355 (1996), 57-64. 

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