Sensitivity of measurement

For sensitivity of measurement, evidently we wish the classical absorption [B in Eq. (4-30)] to be small. Water has (a// )dassicai = 22 x 10 s cm, which is a very small value (water does not absorb sound well). Typical values of (a// )chemicai are 10-10 x 10 s cm. ... 

Quality of analytical equipment specificity, accuracy, precision, and sensitivity of measuring and analyzing equipment determine the reliability of test results. 

The characteristic calibration curve is shown in Figure 11.21 on a logarithmic scale, over a range from 30 to 550°C. In the region between 150 and 450°C, the maximum sensitivity is seen. Beyond 500°C, the calibration curve tends to flatten out dramatically, and the sensitivity of measurement achievable in this region is limited, as shown by the dashed line in Figure 11.21, which represents the relative temperature sensitivity of the observed fluorescence lifetime, smx defined as... 

Alternatively, an assembly of microelectrodes can alleviate some of the problems associated with the individual microelectrodes. Such a random array of microelectrodes (RAM) comprises about 1000 carbon fibres (each of diameter 5-7 pm) which are embedded randomly within an inert adhesive such as an epoxy resin. (The ends of the fibres need to be widely spaced.) The net result is to generate an electrode system with a superior response time and a current which is IfKK) times that of a single microelectrode. By increasing the current in this way, the sensitivity of measurement is further increased. 

Any unwanted, extraneous, and random disturbance that degrades accuracy and/or precision in the recording or measuring of a signal. The occurrence of noise is manifested in experimental science as a threshold that defines the sensitivity of measurement. 

AMS) measurement of atoms (which provides concentrations). The development of linear accelerator mass spectrometer has significantly increased the sensitivity of measurements, leading to an increase of the limit of ages to be dated, but more significantly to a decrease of sample size to be measured and the measurement time. 

Breakthrough. Eluate radionuclidic purity is determined by Nal scintillation spectrometry on 50 ml of eluate. Samples must be held at least one hour before measurement to allow full decay of Rb-82. To improve sensitivity of measurement, the most prominent 511+514 keV peak is counted. Computations are based upon comparison with an aliquot of Sr-82+Sr-85 solution used to prepare the generator.. Data are expressed in units of yCi Sr-82/ml of eluate/ mCi Rb-82 at end of elution. 

Optimum seed control size in relation to product size and inherent nu-cleation rate of the system (c) Fines trap capacity to assure effective control of seed size chosen (d) Phasing of seed rate adjustments in relation to corrections or changes in product size and (e) Sensitivity of measurement and control procedures to assure effective and steady size control of product. 

TABLE 18.1 Sensitivity of Measurement Parameters to H2O2 wt% Concentration in Cabot EP-C5001 and H2O2 Blend. 

Statistical Fluctuations. Thermodynamic systems in general present unordered random deviations from equilibrium referred to as statistical fluctuations. Even slight fluctuations are apt to give rise to experimentally accessible effects. Thus, as shown by Smoludiowski, local fluctuations in density in gases and liquids cause light scattering by optically transparent media. Attempts to raise the sensitivity of measuring devices are fmled by... 

As the bomb transient demonstrated the value of radiocarbon as an environmental tracer, availability of tandy might lead to small-scale tracer experiments designed to study the allocation of carbon by plants in namral environments. Because of the high accuracy and high sensitivity of measurements, such tracer experiments can be carried out at a few times the ambient atmospheric ratio and hence... 

This equation forms the basis of quantitative analysis by absorption photometry. When is 1 cm and c is expressed in moles per liter, the symbol e is substituted for the constant a. The value for c is a constant for a given compound at a given wavelength under prescribed conditions of solvent, temperature, pH, etc., and is called the molar absorptivity. The nomenclature of spectrophotometry is summarized in Table 3-2. Values for e are useful to characterize compounds, establish their purity, and compare sensitivities of measurements obtained on derivatives. Pure bilirubin, for example, when dissolved in chloroform at 25 °C, has a molar absorptivity of 60,700+1600 at 453 nm. The molecular weight of bilirubin is 584. Hence a solution containing 5mg/L (0.005 g/L) should have an absorbance of... 

The high diagnostic sensitivity of measurements of plasma free or urinary fractionated normetanephrine and metanephrine makes these tests the most suitable choice for the initial work up of a patient with a suspected pheochromocytoma. Negative results by these tests virtually exclude a pheochromocytoma, whereas negative results by other tests do not. Exceptions include small or microscopic ([Pg.1047]

The organic nonphosphate moiety may be fluorogenic, which would tend to increase the sensitivity of measurement (G17, M32). 

Samples returned to the laboratory after exposure are measured by micrometer prior to laser-moire evaluation micrometer measurements are reproducible only to within 13 micrometers because surface roughness produces an unusually high sensitivity of measurements to placement of the micrometer. Following laser-moire measurements, the samples have in some instances been checked by an electronic dial gage profiling technique. Because there is risk of damage to samples by the stylus of the gage, its use is minimized thus, the statistics are fewer than desired and far less comprehensive than those of the completely nondestructive laser-moire method. Samples are returned to test sites for continued exposure after measurements. 

Shinoda and coworkers [20] found that many O/W emulsions (based on ethoxylated surfactants) undergo a process of inversion to W/O at a critical temperature (PIT). The PIT can be easily measured by following the conductivity of the emulsion as a function of temperature (a small amount of electrolyte, e.g., NaCl is added to increase the sensitivity of measurement). The conductivity of the O/W emulsion increases with increase of temperature until the PIT is reached, above which there is a rapid reduction in conductivity (a W/O emulsion is formed with low conductivity as the continuous phase is now oil). Figure 15.12 shows a schematic representation of the variation of conductivity with temperature increase for an O/W emulsion. At the PIT, the interfadal tension y reaches a minimum, as illustrated in Figure 15.13 for an O/W emulsion. 

Future changes in the health care system may increase the speed with which purchasers switch to generic products. "For illustrative purposes, OTA examined the sensitivity of measured returns on R D to a decline in revenues at an annual rate of 20 percent from the date of patent expiration until the 20th year following approval of the drug. 

Carbon-13 NMR spectroscopy is also widely used to characterize gold compounds. Measurements at the natural abundance (1.11%) require moderately high concentrations, but in many cases specific sites can be enriched to increase the sensitivity of measurement. Cyanides of gold(I) have been studied because of their technological importance... 

RiUe I. Changing the injected sample volume is a powerful way to change dispersion. An increase in peak height—and in sensitivity of measurement—is achieved by increasing the volume of the injected sample solution. Conversely, dilution of overly concentrated sample material is best achieved by reducing the injected volumes. 

In other words, if a sufficient excess of reagent is to be maintained throughout the whole sample zone (say at least fivefold stoichiometric excess), and if the original sample and reagent concentrations are equal, then medium dispersion at must be obtained by the means outlined in the previous section. If sensitivity of measurement is to be increased ... 

Gradient dilution [275, 338], which was first described and used in 1982 [264, 338], is based on the selection of a suitable element of the dispersed sample zone to become the source of the analytical readout. This is done by selecting a time delay (e.g., 10, 12, 14, 16, or 18 s), elapsed from the point of injection 5, as illustrated in Fig. 2.18, right. Since the selected elements of the dispersed sample zone have different dispersion coefficients (Di, D2, I>3,. . . , Fig. 2.18, left), which yield, for a series of injected standard solutions, a sequence of corresponding calibration curves with decreasing slopes, the sensitivity of measurement can be... 

Use of peak area or peak width at continuous flow has not yet been reported, although it is potentially useful. Most frequent applications of kinetic assays (cf. Chapter 7) are aimed at the enhancement of sensitivity of measurement or at the blank correction offered by the kinetic discrimination between analyte-nonrelated initial response of sample material and the analyte-related reaction rate response due to formation of the measurable product. 

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