Retention as a function of the

Variation of solute retention as a function of the eluent pH. Conditions beta-cyclodextrin-silica pure aqueous eluent pH adjusted by HC1. Column temperature 30 C, eluent flow-rate 1 mL/min. 

Fig. 2. Anion exchange separation of trimethylammonium polyfethy-leneimine) Retention as a function of the filtration factor Z (ratio of filtrate volume to cell volume) (4% w/w, 0.01 M sodium salts, pH 8.5) [33]...

When the analyte mobile phase concentration is small, only a negligible fraction of the HR is in the form of a complex, hence its concentration [H] in the eluent can be considered invariant [3]. Both the pairing ion isotherm and the surface potential are unchanged by the presence of the sample ion [31,33]. In this case [20], analyte retention as a function of the mobile and stationary phase concentrations of the HR can be described, respectively, by the following expressions ... 

Vr(csi) is the analyte retention as a function of the eluent concentration, Vo is the total volume of the liquid phase in the column, y Cei) is the volume of adsorbed layer as a function of eluent composition, Kp(cei) is the distribution coefficient of the analyte between the eluent and adsorbed phase, S is the adsorbent surface area, and is the analyte Henry constant for its adsorption from pure organic eluent component (adsorbed layer) on the surface of the bonded phase. 

Figure 9.13. Thermal annealing of ammonium sulfate relative activity of in the form of sulfate (retention) as a function of the time of annealing at 180°C.

Figure 20 Column experiments for Eu retention as a function of the loading in different environments (O) 1 M HNO3, ( ) HNO + 3.6 M NaNO, and ( ) ILW simulate. (From Ref. 80.)...

Equation 41 thereby provides the means of representing solute inverse retentions as a function of the concentration of mobile-phase additive irrespective of the valency of eitheri For example, in those instances where y X, the relation reduces to ... 

Fig. 4-39. Monovalent cation retention as a function of the eluant ionic strength. - Separator column lonPac CSl eluant HCl flow rate 2.3 mL/min detection suppressed conductivity.

Any improvement in resolution obtained by increasing ki generally comes at the expense of a longer analysis time. This is also indicated in Figure 12.11, which shows the relative change in retention time as a function of the new capacity factor. Note that a minimum in the retention time curve occurs when b is equal to 2, and that retention time increases in either direction. Increasing b from 2 to 10, for example, approximately doubles solute B s retention time. 

Kranzler and Van Kirk (2001) included 11 acamprosate studies in a metaanalysis involving more than 3,000 subjects. The magnitude of the advantage shown by acamprosate over placebo in those studies varied as a function of the outcomes examined, which included the percentage of patients who were abstinent throughout the study, cumulative abstinent days, and the rate of study retention, all of which favored the active medication. Acamprosate yielded outcomes that were, on average, 7%—13% better than those shown by individuals who received placebo. 

Contrary to EFA which calculates a PCA of a sub data matrix to which rows are added, in fixed-size window EFA a small window of rows is selected which is moved over the data set (see Fig. 34.30). Typically, a window of seven consecutive spectra is used. At each new position of the window a PCA is calculated and the eigenvalues associated with each PC are recalculated and are plotted as a function of the position of the window. This yields a number of eigenvalue-lines. Figure 34.31 shows the eigenvalue-lines obtained for a simulated pure LC-DAD peak. In the baseline zones (null spectra) all eigenvalue-lines are noisy horizontal lines. In the selective retention time regions (one component present) the eigenvalue-line associated with the first PC follows the appearance and disappearance of the... 

A dissimilarity plot is then obtained by plotting the dissimilarity values, dj, as a function of the retention time i. Initially, each p 2 matrix Y, consists of two columns the reference spectrum, which is the mean (average) spectram (normalised to unit length) of matrix X, and the spectrum at the /th retention time. The spectrum with the highest dissimilarity value is the least correlated with the mean spectrum, and it is the first spectrum selected, x, . Then, the mean spectrum is replaced by x, as reference in matrices Y, (Y, = [x j x,]), and a second dissimilarity plot is obtained by applying eq. (34.14). The spectrum most dissimilar with x, is selected (x 2) and added to matrix Y,-. Therefore, for the determination of the third dissimilarity plot Y, contains three columns [x, x 2 /]> wo reference spectra and the spectmm at the /th retention time. 

In summary, the selection procedure consists of three steps (1) compare each spectrum in X with all spectra already selected by applying eq. (34.14). Initially, when no spectrum has been selected, the spectra are compared with the average spectrum of matrix X (2) plot of the dissimilarity values as a function of the retention time (dissimilarity plot) and (3) select the spectrum with the highest dissimilarity value by including it as a reference in matrix Y,-. The selection of the spectra is finished when the dissimilarity plot shows a random pattern. It is considered that there are as many compounds as there are spectra. Once the purest spectra are available, the data matrix X can be resolved into its spectra and elution profiles by Alternating Regression explained in Section 34.3.1. 

FIG. 20-71 Air fractionation by membrane. O2 in retentate as a function of feed fraction passed through the membrane (stage cut) showing the different result with changing process paths. Process has shell-side feed at 690 kPa (abs) and 298 K. Module comprised of hollow fibers, diameter 370 )J,m od x 145 )J,m id x 1500 mm long. Membrane properties a = 5.7 (O2/N2), permeance for O2 = 3.75 x 10 Barrer/cm. Courtesy Innovative Membrane Systems/... 

In practice, it is more difficult to optimize resolution as a function of the relative retentlvity than to optimize retention. Thus, unless the mixture is very complex or contains components that are particularly difficult to separate it may be possible to optimize a particular separation using the linear equation (1.72) as demonstrated by Bttre [177]. Figure 1.13 illustrates the relative change in peak position for a polarity test mixture with two identical, serially coupled open tubular columns, coated with a poly(dimethylslloxane) and Carbowax 20 M stationary phases, as a function of their relative retentlvity on the second column. The linear relationship predicted by equation (1.72) effectively predicts the relative peak positions and indicates that a nearly... 

The co plAxlty of the retention proceas In RPC haa encouraged activity in non-chroaatographlc techniques to evaluate parameters appropriate for predicting retention as a function of mobile phase composition. Preliminary studies have indicated that solvatoChroaic methods can provide some useful insight into the retention process. The scale of solvent strength, based on... 

For the example of toluene given above, the external standard method can be converted into an internal standard method by adding anisole (an appropriate internal standard) to both standard and sample. The retention time of anisole is 4.5 minutes if analyzed by the method above. To calibrate the internal standard method for toluene, toluene standards of concentration 0.3 to 1.5 mg/ml containing 0.5 mg/ml anisole were prepared. The detector response as a function of the amount of sample injected is shown in Figure 4B. 

Figure 5. TLC retention factor Rp for poly(methyl methacrylate) on silicagel, as a function of the elution strength of binary solvent (carbontetrachloride, CCl )/ displacer (1,4-dioxane) mixtures. Note the steep increase in Rj, at Efj w 0.38, indicating a sharp adsorption/ desorption transition.

Fig. 3.21. Retention rate of liposome-encapsulated hemoglobin as a function of the time elapsed after the reconstitution of the freeze dried LEH, with different trehalose concentrations as CPA. 1, no trehalose 2, 10 mM 3, 50 mM 4, 150 mM 5, 300 mM trehalose (Fig. 2 from [3.43]).

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