Working curve

In a molded polymer blend, the surface morphology results from variations in composition between the surface and the bulk. Static SIMS was used to semiquan-titatively provide information on the surface chemistry on a polycarbonate (PC)/polybutylene terephthalate (PBT) blend. Samples of pure PC, pure PBT, and PC/PBT blends of known composition were prepared and analyzed using static SIMS. Fn ment peaks characteristic of the PC and PBT materials were identified. By measuring the SIMS intensities of these characteristic peaks from the PC/PBT blends, a typical working curve between secondary ion intensity and polymer blend composition was determined. A static SIMS analysis of the extruded surface of a blended polymer was performed. The peak intensities could then be compared with the known samples in the working curve to provide information about the relative amounts of PC and PBT on the actual surface. 

The working curves in Figure 7-8 were obtained on known samples,... 

A working curve was constructed for each element from counting data obtained on a number of chemically analyzed standards apparently no. background correction was necessary. By use of these simple curves, and without allowing for absorption or enhancement effects, satisfactory approximate results were obtained for both iron and manganese, as is shown by the data in Table 7-10, which are representative of those for a series of 40 samples. 

The second subdivision was mentioned in Section 8.2, where it was indicated that background determination and correction could be omitted if a more serviceable working curve resulted in this way. See also Section 7.14 and Figure 7-8. 

Ceramics and minerals present many common problems, but ceramics warrant special treatment because elements of low atomic number predominate in them and they consequently offer x-ray emission spectrog-raphy of the light elements an excellent opportunity to prove its usefulness. Scott,8 in making this clear, emphasized the absorption and enhancement effects to be expected, and pointed out the need for careful sample preparation. By use of a General Electric XRD-5 spectrograph and associated equipment, he set up working curves for alumina, silica, potash, lime, phosphate, titania, and iron oxide in clays, refractories, and other ceramic materials. 

In the case of 0-pipettes, the collection efficiency also decreases markedly with increasing separation. The situation becomes more complicated when the transferred ion participates in a homogeneous chemical reaction. For the pseudo-first-order reaction a semiquantita-tive description is given by the family of dimensionless working curves calculated for two disks (Fig. 6) [23]. Clearly, at any separation distance the collection efficiency approaches zero when the dimensionless rate constant (a = 2kr /D, where k is the first-order rate constant of the homogeneous ionic reaction) becomes 1. 

Modem absorption instruments can usually display the data as transmittance, %-transmittance, or absorbance. An unknown concentration of an analyte can be determined by measuring the amount of light that a sample absorbs and applying Beer s law. If the absorptivity coefficient is not known, the unknown concentration can be determined using a working curve of absorbance versus concentration derived from standards. 

Working curve for the determination of magnesium with molybdenum as internal standard. 

Fig. 4. Pb and Hg LIBS emission lines. Insert set. is analytical working curve analysis.

In addition, very few observations are pristine and basic measurements such as angular deviation of a needle on a display, linear expansion of a fluid, voltages on an electronic device, only represent analogs of the observation to be made. These observations are themselves dependent on a model of the measurement process attached to the particular device. For instance, we may assume that the deviation of a needle on a display connected to a resistance is proportional to the number of charged particles received by the resistance. The model of the measurement is usually well constrained and the analyst should be in control of the deterministic part through calibration, working curves, assessment of non-linearity, etc. If the physics of the measurement is correctly understood, the residual deviations from the experimental calibration may be considered as random deviates. Their assessment is an integral part of the measurement protocol and the moments of these random deviations should be known to the analyst and incorporated in the model. 

Working curves such as those represented in Figure 2.5, derived from the computation of equation (2.12) or (2.13), may be used for the kinetic... 

Numerical Computations. Simulations. Diagnostic Criteria. Working Curves... 

The parameter k° is generally calculated from the working curve shown in Figure 9.8... 

Figure 9 Working curve to calculate k° from the parameter AEp...

Should it be impossible to measure td, the problem can be overcome by using the working curve reported in Figure 13.9... 

Figure 13 Working curve to obtain the kinetic parameters for a CrEr mechanism from the current ratio iprjipf...

The conditions in which ipT/ipr assumes values between 0.45 and 0.95 are the best for calculating the rate constant of the following reaction. In fact, from the working curve reported in Figure 16, based on the current ratio ipT/ipf, one can determine the value of /Cf x. 9 Since x is easily calculated, being the time necessary to move from E° (calculated under the conditions where ipr/ipt =1) to the inversion potential E(, k is determined. 

Figure 16 Working curve to calculate the rate constant kffor an ErC( mechanism from the current ratio ipr/ipf...

The second method is based on the measurement of the current ratio Zpr/Jpf at a given scan rate. Through the use of the working curve reported in Figure 18, one is able to determine k210... 

Figure 18 Working curve to obtain the dimerization constant from the current ratio iprlip/...

When the value of kf is such that one does not obtain an S-like curve, kf can be determined from the working curve reported in Figure 22a,9... 

Figure 22 Working curve for the catalytic regeneration of the reagent following a reversible (a) or irreversible (b) electron transfer...

However, if the redox couples Ox/Red and Ox /Red have sufficiently different standard potentials, can be also calculated using the working curve reported in Figure 16. In fact, considering the process simply as a reversible electron transfer followed by an irreversible first-order chemical reaction (see Section 1.4.2.2), one measures only the current ratio /pr//pf of the first couple Ox/Red. Obviously, the return peak must be recorded before the second process begins to appear this means that the direction of the potential scan must be reversed immediately after having traversed the first forward peak. 

Figure 24 Working curve for the determination ofkfin an ErC,Er mechanism in which the second electron transfer is more cathodic than the first one. v in V s ...

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