Sentinel method

Figure S.22 Experimental design as used in the Sentinel method of Glajch et al. [542). Figure taken from ref. (565). Reprinted with permission.

The term Simplex design (or Simplex lattice design) is unfortunate. It creates confusion between the Simplex method for optimization (section 5.3) and the Sentinel method of Glajch et al., which is a very different method by all accounts. To avoid further confusion, we will not use the word Simplex in connection with the Sentinel method. 

Summary of mobile phase compositions to be used in the experimental design for the Sentinel method. 

Summary of mobile phase compositions to be used in the experimental design for the Sentinel-method as applied to LSC. Selectivity parameters for LSC solvents according to the experimental design of figure 5.22. 

So far, an empirical approach that neglects the specific problems of LSC has appeared more feasible. Antle [572] demonstrated the applicability of the Sentinel method to LSC, using mixed mobile phases corresponding to table 5.4a, i.e. mixing the individual binary mixtures according to their volume fractions. This yielded some success, although admittedly not all solvents were iso-eluotropic. 

Glajch et al. [573] have expanded the Sentinel method to include the simultaneous optimization of the stationary phase. They applied the complete seven-point experimental... 

The parameter space in the original Sentinel method is restricted to a series of iso-eluotropic solvents, which means that only a very small fraction of all possible quaternary mixtures is considered. This is illustrated in figure 5.27a. 

The advantages of the use of fixed regression designs, including multi-dimensional window diagrams and the Sentinel method, can be summarized as follows ... 

If the parameter space is reduced to a two-dimensional triangle (Sentinel method), then a better optimum outside this plane may be neglected. 

For the optimization of programmed solvent LC the Sentinel method starts by establishing a suitable binary methanol-water gradient. The approach of Snyder described above may be used for this purpose. For example [627], a gradient from 20 to 100% methanol (in water) in 20 minutes may be the result. 

The Sentinel gradient optimization method, by analogy with the isocratic Sentinel method, requires a minimum of 7 chromatograms to be recorded before the optimum conditions can be predicted and it requires the retention data of all solute components to be established at each experimental location. 

The Sentinel method of Glajch and Kirkland described above involves the measurement of retention data under gradient conditions and the direct optimization of the selectivity,... 

It is interesting to note that the gradient predicted by Jandera et al. could not have been arrived at using the Sentinel method described in figure 6.13. 

The Sentinel method is the outstanding exponent of the group of interpretive methods, as it has already been applied successfully for selectivity optimization in programmed solvent LC. However, other interpretive methods, based either on fixed experimental designs or on iterative procedures, can be applied along the same lines. It was seen in section 6.3.2.3 that the extension of the Sentinel method to incorporate gradient optimization was fairly straightforward. 

Fig. 9.11 Sentinel hole method of monitoring corrosion of a pipe wall...

A further insight is that the best workflow depends on a combination of factors that can in many cases be expressed in closed mathematical form, allowing very rapid graphical feedback to users of what then becomes a visualization rather than a stochastic simulation tool. This particular approach is effective for simple binary comparisons of methods (e.g., use of in vitro alone vs. in silico as prefilter to in vitro). It can also be extended to evaluation of conditional sequencing for groups of compounds, using an extension of the sentinel approach [24]. 

Rapid immunohistochemical study of frozen sections is necessary for intraoperative diagnosis in some cases. Rapid immunostaining is also helpful in confirming or excluding tumor clearance in resection margins or in detecting micrometastases in sentinel lymph nodes in breast cancer patients. Two methods to immunostain frozen sections are the enhanced polymer one-step staining (EPOS) system and the EnVision system both systems are detailed later. 

Two sentinel species were caught in the reference and exposure zones in sufficient numbers (at least 12 fish) for statistical interpretation. The data for the white sucker, Catastomus comersoni and longnose sucker, Catastomus catastomus, are listed in Table 7. All endpoints (Beak International, 2000) and comparisons of exposure and reference area data involved appropriate statistical methods. Any significant difference or significant interaction in any endpoint was considered potentially mill-related. 

Figure 6.13 Figure illustrating the 7 linear gradients used in the Sentinel optimization method for programmed solvent LC. Initial and final compositions of the gradients are listed in table 6.4. 

EPA (2006). Sentinels Detection Methods and Chemical Decontamination Health Risk Key Components of EPA s Safe Building Program. US Environmental Protection Agency, Washington, DC. 

Define and discuss sentinel organisms as ecosystem monitors. What are advantages of using this method ... 

Aged Rat Study. Using the sentinel rats in the 2-year study, 15 male and 15 female rats (18 months old) shall be gavaged at the middle dose. Blood samples shall be taken at five time points (to be specified by NTP), with three animals bled at each time point. Each rat shall be bled only once. Test chemical concentrations shall be determined in plasma using a validated analytical method. 

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