Resolution window diagram

FIGURE 5.6 (A) The resolution window diagram for RP-gradient-elution separation of phenylurea herbi-... 

Fig. 1.30. (A) The resolution window diagram for the gradieni-elulion separalion of a mixture of eight phenyluiea herbicides on a Separon SGX. 1.5 tm. silica gel column (150 x 3.3 mm i.d.) in dependence on the initial concentration of 2-propanol in n-hcpiane at ihe slart of the gradicni. A. with optimum gradient volume Vc, - 10 ml. Column plate number N = 5000. compounds as in Fig. 1.23. (B. C) The separation of the eight phenylurea herbicides with optimised gradient-elution conditions (maximum resolution in (A)) with gradients from 12 to 38.6 2 2-propanol in n-hcptanc in 7 min (B) and from 25 to 37.5 2 2-propanol in fi-heptane in 5 min (C). Flow rale I ml/min.

Fig. 3 Top The resolution window diagram for RP gradient elution separation of phenylurea herbicides on a Separon SGX Cl8 7.5-pm column (150 x 3.3 mm ID) in dependence on the initial concentration of methanol in water at the start of the gradient A with optimum gradient volume Vq = 13 mL. Column plate number A = 5000 sample compounds hydroxymetoxuron (1), desphenuron (2), phenuron (3), metoxuron (4), monuron (5), monolinuron (6), chlorotoluron (7), metobromuron (8), diuron (9), linuron (10), chlorobromuron (11), and neburon (12). Bottom The separation with optimized binary gradient from 24% to 100% methanol in water in 73 min. Flow rate = 1 mL/ min T=40°C.

Although a resolution window diagram such as Figure 4.11 presents a much more useful view of the overall separation, its construction is more complex than a simple separation factor window diagram it requires measurement of both... 

FIGURE 5.17 Plots of ko versus a for an arbitrary five-component mixture (a) and the resulting resolution window diagram (b). Vertical broken lines indicate a values that result in coelution of the corresponding component pairs. The value of ao gives the volume fraction of stationary phase A that will give the greatest resolution of the critical pair. 

Optimization procedures are used to determine which of these (1)a values will obtain the greatest resolution of the critical pair (36). Figure 5.17b shows a resolution window diagram where the resolution Rs of the critical pair is plotted against the volume fraction of phase A. The zero-resolution points are defined by the (t)A values that result in the crossing of the various plot pairs in Figure 5.17a. Between the zero-resolution points are windows of various amplitude, which... 

Simultaneous Optimization of Density and Temperature. Although near-baseline resolution was achieved for all eight sample components via the optimization of a single variable (density), as illustrated in Figure 1, a better (or in rare cases, equal) result will always be obtained if all variables of interest are optimized. The window diagram method is now considered for the simultaneous optimization of density and temperature for the separation of the eight component sample of Table VI, to provide a comparison with the SFC separation obtained with the density-only optimization (Figure 6). 

Shown in Figure 10 is the chromatogram acquired at the optimum predicted by CRF-4. Baseline resolution of all 8 components was achieved in about 27 minutes, except for components 2-4 which were almost baseline resolved. Additional evidence for the accuracy of the retention model (equation 9 and Table VI) employed for this window diagram optimization is evident in Table VIII, where predicted and measured retention factors differed by less than 15%. The slight positive bias observed for all solutes at the optimum conditions in Table VIII was coincidental averaged over the entire parameter space the bias was almost completely random. 

There is a clear analogy between this type of figure and a window diagram. In the white area, which may be called a window, the resolution will be at least 1.5 (for the example in figure 5.25) for all pairs of peaks. This is illustrated in figure 5.26, which shows the... 

Fig. 1.23. Top the window diagram (the dependence of the resolution on the concentration of 2-propanol in ri-heptane as the mobile phase) for a mixture of eight phenylurea herbicides on a Separon SGX, 7.5 pm. silica gel column (150 x 3.3 mm i.d.). Bottom the separation with optimised concentration 1953 2-propanol in the mobile phase for maximum resolution. Column plaie number N = 5000. T = 40°C. flow rate 1 ml/min. Sample compounds neburon (/). chlorobromuron (2). 3-chloro-4-methylphenylurea (7). desphenuron (4). isoproturon (5). diuron (6). metoxuron (7). dcschlorometoxuron (S).

Fig. 4 (A) The window diagram (the dependence of the resolution on the concentration) of 2-propanol in n-heptane as the mobile phase. (B) The separation with an optimized concentration of 19% 2-propanol in the mobile phase for maximum resolution. Compounds and column are as in Fig. 3.

Figure 18.14 Window diagram. The separation was performed with a linear gradient from 0 to 45% B and the optimum runtime needs to be found out. (a) Gradient in 15 min (b) gradient in 45 min with some elution orders reversed (c) window diagram calculated from the initial two experiments with a linear relationship between retention time and %B assumed the plot shows the resolution / of the peak pair which is critical under the respective conditions it is necessary to use long gradient runtimes to obtain a good resolution (d) optimized chromatogram with 0-45% B in 80 min, but separation is already finished after 45 min and 25% B.

The constants a, b, and m in eqn [3] depend on the solute and on the chromatographic system. b = (ka) " , where ka is the retention factor in a pure nonpolar solvent. Equation [2] or [3] can be used as the basis of optimization of the composition of two-component (binary) mobile phases in NPLC, using a common window diagram or overlapping resolution mapping approach, as illustrated in an example in Figure 3. 

Single-parameter optimization employs several experiments at preselected values of the optimized parameter (such as the concentration of the strong solvent in a binary mobile phase, pH, temperature) to predict the resolution as a function of the optimized parameter using empirical or simple model-based calculations. Then, plots are constructed (the window diagrams ) in which the range of the optimized parameter is searched for the value that provides the desired resolution for all adjacent bands in the chromatogram in the shortest time. An example of a window diagram (Pig. 5) illustrates the approach adopted for the optimization of a binary mobile phase in NPLC. 

FIGURE 2.10 Window diagram for the separation of 2-phenyIpropionic add (PPA), phenylsucdnic acid (PSA), 4-hydroxybenzoic acid (40H), and benzoic acid (BA). The highest point under the composite curve offers the best resolution. This occurs at a pH 4.1 with an a value of approximately 1.5. 

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