Optimized LSC

Activation of the Optimized LSC Cathode by Loading nm-Sized Pt Catalysts... 

It can be concluded that with the change of the deposition technique from screen-printing to reactive sputtering PVD for applying the CGO layer, significant progress was made. Thus, in combination with the optimized LSC(F) cathode, a power output of almost 2 W cm (2.7 A cm ) was achieved at 800 °C and 700 mV. 

Figure 41.6 presents a schematic optimized LSC that absorbs in the total spectral range and emits at longer wavelengths (without overlap of absorption and... 

White reflecting coating Figure 41.6 Profile of the optimized LSC (more details are provided in Table 41.2). 

Eqn.(3.73) suggests that any mixture of two solvents with the same ° value (iso-eluotro-pic solvents) will also have the same eluotropic strength. This would allow the application of a similar strategy for the definition of iso-eluotropic multicomponent mobile phase mixtures as was used for RPLC in section 3.2.2.1. In practice, the situation in LSC has proved to be more complicated, because an effect described as solvent localization limits the validity of eqns.(3.72) and (3.73) if polar components (such as acetonitrile or methyl t-butyl ether) are present in the mobile phase. This makes it difficult to calculate the composition of iso-eluotropic mixtures for LSC with sufficient accuracy for optimization purposes [360-363]. 

Table 3.10d lists the parameters for LSC. Again, most separations may be optimized by optimizing the eluotropic strength (primary parameter) and the nature (secondary parameter) of the mobile phase. The latter parameter involves the preparation of different iso-eluotropic mixtures containing different solvents, or small quantities of very polar components ( modulators ). As in the case of RPLC, there are several additional parameters that are not frequently exploited. 

Polar chemically bonded stationary phases (section 3.2.2.2) may be used as an alternative stationary phase for both RPLC and LSC, if variations in the mobile phase do not result in an adequate separation. If polar CBPs are used in combination with more polar mobile phases (reversed phase mode), then table 3.10c may be used to find the most appropriate optimization parameters. If operated in the normal phase mode, table 3.1 Od... 

An important advantage of the Simplex method is that it does not rely on any chromatographic model and does not require any chromatographic insight. This implies that a Simplex optimization program can be applied to LSC as well as to RPLC without any modifications [506]. This is not true for many other methods as will be discussed in section 5.5.1. 

Snyder, Glajch and Kirkland [570) introduced two new parameters to describe the selectivity effects in the optimization triangle for LSC. If methylene chloride (MC), acetonitrile (ACN) and methyl t-butyl ether (MtBE) are used as the preferred modifiers in n-hexane, then an empirical solvent selectivity parameter (m) can be defined which is low for methylene chloride and can be made equal for the other two binary solvents. The latter is achieved by adding the appropriate amount of methylene chloride to the hexane-ACN binary. Addition of MC is required at any rate, because hexane and ACN are not miscible in all proportions. By definition we can assume m to equal zero for the hexane-MC binary mixture and m to equal one for the two other binaries. 

In eqns.(6.1) and (6.1a) a, b9 c and d are constants. Because

concave gradient (figure 6.2d) is optimal for LSC. 

The pattern of the variation of retention with composition in LC is affected by the choice of both the stationary and the mobile phase. The optimum shape of the gradient for unknown wide range samples is dictated by the phase system. Linear or slightly convex gradients are optimal for RPLC. Concave gradients are optimal for LSC. 

The combination of these two factors determines the required shape of an LSS gradient. Linear gradients were shown to result for RPLC in section 5.4, whereas a concave gradient was found to be optimal for LSC in section 6.2.2. 

A strategy for the optimization of gradient programs based on the actual retention behaviour of some sample components has been described by Jandera and Chura5ek [623, 624]. This approach relies on the possibility to calculate retention and resolution under gradient conditions from known retention vs. composition relationships and plate numbers. Both typical RPLC (eqn.3.45) and LSC (eqn.3.74) relationships can be accommodated in the calculations and linear, convex and concave gradients are all possible because of the use of a flexible equation to describe the gradient function. This equation reads... 

When each of the various types of LC was discussed earlier in this chapter, the mobile phase was one of the topics included, but a more comprehensive discussion of these liquids, their properties, and their optimal use in LSC and BPC is needed. This section will describe several ways to select the best solvent mixture for a separation. A more comprehensive discussion on the optimization of selectivity has been given by Glajch and Kirkland.63... 

Determination of the time to equilibrium (ET) The ET is determined by dialyzing freshly spiked plasma containing the high (10 xg/mL) and intermediate (0.05 tig/mL) test concentrations against PBS. At time points 1, 2, 3, 4, and 6 hours of dialysis, a small sample/50 pL) of plasma and PBS is removed from each cell. And the concentration analyzed by LSC or LC/MS-MS. The optimal ET is then determined. 

Finally, we will summarize here all the correlational equations and experimental solvent parameters required for predictions of solvent strength and selectivity in LSC, and discuss their significance in terms of mobile-phase optimization strategies. 

Solvent selectivity effects in LSC are accounted for by terms (i), (ii), and (lil) of Eq. (34). We will first discuss solvent-strength selectivity term (i) and solvent-solute localization selectivity term (ii), leaving hydrogenbonding selectivity term (iii) to the following section. As already indicated, solvent-strength selectivity term (i) is of limited value in optimizing retention in LSC. This effect is directly based on the validity of Eq. (8),... 

This relationship has been experimentally verified for numerous mobile phases (and different solvents) and a wide variety of solutes, with both alumina (IS) and silica (18) as adsorbents. Some examples of the applicability of Eq. (31a) in these LSC systems are given in Fig. 15a (alumina) and Fig. 15b (silica). The use of 3-solvent or 4-solvent mobile phases (18, 20) allows the continuous variation ofm while holding e° constant, which greatly facilitates retention optimization by maximizing a without changing c°. 

Solvent-specific localization is generally only one-half to one-third as Important as solvent-solute localization in affecting a values (18). However, its effects are nevertheless important in overall solvent-optimization strategies for LSC (see Section 1II,E). 

In order to enhance the steps (3)-(5) on the LSC cathode with the optimized microstnicture (sintered at 1050 °C with 1.0 wt% polymer), nm-sized Pt particles were dispersed on the LSC surface." In this case, the following reaction steps are expected to be activated greatly by the Pt-loading and high Oy gas-diffusion rates in the LSC layer,... 

Figure 14. Polarization curves (IR-free, measured in air) at various LSC cathodes at Fceii = 800 °C. original one (sintered at 1050 °C without polymer), O the optimized microstructure (sintered at 1050 °C with 1.0 wt% polymer), Pt-catalyzed (0.1 mg-Pt/cm loaded on the optimized one).

The measurements by LSC are rapid and with optimal cell density on the slide up to 5000 cells can be measured per min. The accuracy and sensitivity of cell fluorescence measurements by LSC are similar as with advanced... 

If the index of refraction of the substrate material is increased, the fraction of emission trapped in the plate is also increased. It has been shown (, 5 ) that the optimal index for LSCs with no antireflection coating is about 2. Surface reflection losses become important for higher indices, unless antireflection coatings are used. 

What about the optimal efficiency of an LSC The model we used to compute this optimal efficiency assumes that the dye in an LSC absorbs all of the solar flux from the peak of its absorption... 

When some commercial surfactants exhibited a precipitous drop in and efficiency between 0.5 and 5% water content, as did the nonionic surfactants Triton X-100 or Triton N-101, others behaved in a manner similar to our contrived nonionic-anionic surfactant mixtures. It is thus apparent that accurate calculation of the relative radioactivity of emulsified aqueous samples depends on rigorous uniformity of sample preparations. Optimal proportions of surfactants, surfactant content, and water content will depend on the nature and amount of the solute being counted. The usual methods of quench correction in LSC must be examined very carefully, inasmuch as they will usually not be adequate for determining absolute counting efficiency. 

In our laboratory, the following procedures for LSC of Fe in the plasma was found to be optimal. 1 ml of plasma is placed in a glass LSC vial. 1 ml of a mixture of Soluene-350 isopropanol (1 2 v/v) is added, followed by a mixture of 15 ml Instagel 0.5N HCl (9 1 v/v). When plasma hemoglobin must be removed from plasma samples before counting, the procedure is modified as follows. Plasma hemoglobin is precipitated by the method of Cavill et al. (1976). 2 ml of supernatant is... 

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