Recovery, function

In this process the addition of water vapor to the sweep stream can be controlled so that the water activity of the gas phase equals that of the beverage. When this occurs, there is no transport of water across the membrane. The water content of both the beverage feed and the sweep stream is kept constant. These conditions must be maintained for optimum alcohol reduction. The pervaporation system controls the feed, membrane, airstream moisture level, and ethanol recovery functions. An operational system has been developed (13). 

Specifications for chromatographic packings often describe maximum loading in terms of the maximum capacity of a unit quantity of the packing to bind some analyte, often a well characterized protein such as bovine serum albumin. The static loading capacity35 is very different from functional capacity,2 which is the maximum amount of a particular feedstock that can be loaded and still achieve acceptable purification and recovery. Functional capacity is determined empirically for each type of load and associated set... 

Commonly the absence of systematic errors is tested by recovery studies. The estimation of recovery by analyzing only one standard, as frequently be done, can give misleading results as can be seen from Fig. 4.2. In case of combined and nonlinear systematic deviations there can occur points of accidental congruence that can be hit. Therefore, if at all possible, there should be estimated the entire recovery function. However, at least two different standards should be analyzed. 

It should be noted that the spatial model contains additionally to the calibration and evaluation functions the recovery function, too. These three functions represent the projection of the spatial C-E-R function onto the corresponding planes, as shown in Fig. 6.3. 

Fig. 6.3. Three-dimensional model of calibration, analytical evaluation and recovery spatial model (A) the three relevant planes are given separately in (B) as the calibration function with confidence interval, in (C) as the recovery function with confidence interval, and in (C) as the evaluation function with prediction interval (D)... 

Accuracy. In general, the accuracy of analytical results is assured by recovery studies (Wegscheider [1996] Danzer [1995] Burns et al. [2002]). According to the recovery function in the general three-dimensional calibration model (see Fig. 6.3), common studies on systematic deviations (Fig. 4.3), and Eqs. (4.2) and (4.3) the following recovery formulae... 

Another way to verify the accuracy of a method (I) under validation is the analysis of a given set of test samples with graduated analyte concentrations by both methods, (I), and an independent one (II), which is known to be accurate. The special recovery function in this case is given by Eq. (6.47b). 

Trueness. Absence of systematic errors can be tested traditionally by means of recovery functions see Sect. 6.1.2, Fig. 6.3C Burns et al. [2002]. For this reason the concentration estimated by the model, x, is compared with the true concentration value, xtrue, by a regression model... 

A recent innovation to improve recovery functions is a variable-speed submersible pump. When used with electronic controls, it is possible to select a fluid surface elevation and adjust the pumping rate periodically to maintain that fluid level at that elevation. Another adaptation of existing control technology uses an electrically adjustable valve to throttle the pump output. As the fluid level declines, the throttle restricts flow to prevent a further decline. 

In order to obtain a general model of the creep and recovery functions we need to use a Kelvin model or a Kelvin kernel and retardation spectrum L. However, there are some additional subtleties that need to be accounted for. One of the features of a Maxwell model is that it possesses a high frequency limit to the shear modulus. This means there is an instantaneous response at all strains. The response of a simple Kelvin model is shown in Equation 4.80 ... 

The recovery can be calculated either at each level separately as a percent recovery, or as a linear regression of the found analyte vs. the added one (recovery function) (Table 3). 

With respect to the recovery function, the slope and intercept can be tested vs. the theoretical values of 1 and 0 (by their 95 /o CIs) or vs. acceptable limits for deviation. Due to the different weighting effects, the two approaches might lead to different results. The percent recovery calculation gives easily interpretable results and should therefore be preferred, at least for narrow working ranges. 

Fig. 6. 23. A Glucose profile of a single test person (comparable to that of Fig. 6.13), cgiuc reference value of glucose concentration, o, and the predicted glucose values of NIR measurements, , evaluated by PLS. B Recovery function and fitted calibration line of the PLS calibration (number of included wavelengths n = 56,6 factors). C Recovery function and fitted calibration line of the RBF calibration (number of included wavelengths n = 56,10 hidden layers), according to Fischbacher et al. [1995]...

It is necessary to determine the recovery function and the recovery rate in order to detect a possible error in the analytical result by the process of sample preparation or even by the sample matrix itself. 

The recovery function should be linear with y axis intercept Op = 0 and slope bp = 1. If ap7 0 a constant-systematic error is present, if bp there is a proportional-systematic error of sample preparation. 

The recovery function and rate can be determined for each individual step of sample preparation. This allows the specihc improvement of the critical steps. Afterwards the same procedure can be performed with spiked samples for the determination of matrix effects. 

Calculate the recovery function and the recovery rate. Judge the recovery function. 

Change the time scale again to days and calculate the recovery function. 

The Emax model is a simple function to implement in NONMEM and has the advantage of parameterization that is reasonably familiar, making the modeling results relatively easy to interpret by individuals who are not familiar with modeling. The patient status at any time t is described as the sum of the basehne status So and some recovery function that has a maximum of 5n,ax- The time to half maximal recovery is Sso-... 

Figure 6.9 illustrates the recovery function for the analysis of protein contents in wheat. The predictions correspond here to... 

Figure 6.9 Recovery function for resubstitution of samples in case of inverse OLS calibration of protein (mass%) by means of NIR spectra.

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