Phase adsorption

When the Ba loading increased up to 10% (w/w) (Pt—Ba/ y-AljC 1/11.5/100 w/w sample, Figure 6.18c), the reduction step was longer than in the previous case, in line with the higher amounts of NOx species that the catalyst was able to store during the previous adsorption phase (see Figure 6.6). Also in this case, low amounts of NO were found at the reactor outlet so that the process presented a selectivity rate close to 100% (Figure 6.19). 

The surfactant is an important component of this process and acts to stabilize the growing polymeric particles by surface adsorption. Phase separation and the formation of solid particles occur before or after termination of the polymerization process [42]. Polymerization can occur in some systems without the presence of surfactants [40]. Various particulate systems have been prepared by this method, including poly(styrene) [43], poly(vinylpyridine) [44, 45], poly(acrolein) [46, 47], and poly(glutaraldehyde) [48-50],... 

On Ag(llO), three voltammetric peaks have also been observed [265], owing to adsorption, phase transformation, and deposition on the previously formed mono-layer. 

The Cu(100) ( /2 x 2A/2)R45°-0 surface reconstruction has an oxygen coverage of 0.5 ML, but there have also been many reports in the literature of a Cu(100)c(2 x 2)-0 phase which would also involve a coverage of 0.5 ML. In truth, in quite a number of these earlier reports no ordered structure was actually observed experimentally and the adsorption phase studied was simply assumed to be this previously reported ordered phase. Reviewing this early literature thus requires some care Indeed, a careful study of the relative intensities of the 2 and order... 

Carotenoid separations can be accomplished by both normal- and reversed-phase HPLC. Normal-phase HPLC (NPLC) utilizes columns with adsorptive phases (i.e., silica) and polar bonded phases (i.e., alkylamine) in combination with nonpolar mobile phases. In this situation, the polar sites of the carotenoid molecules compete with the modifiers present in the solvent for the polar sites on the stationary phase therefore, the least polar compounds... 

If an inert material is initially adsorbed on the fixed bed comprising an appropriate adsorbent and a catalyst, the heat of adsorption—having the same order of magnitude as the latent heat of evaporation—will be released (Figure 15). Since no reaction takes place in this phase, moderate temperature excursions are acceptable, and recycle flows over external heat exchangers or injection of liquid adsorptives may serve as heat sinks. In the subsequent reaction phase, the heat liberated by an exothermic reaction on the catalyst is taken up by the desorption of the inert from the previously loaded neighboring adsorbent particles. As long as this desorption occurs, the heat of reaction will not lead to major temperature increases. Sooner or later, of course, the adsorbent will be depleted and the temperatures will drift upward, at which point the adsorption phase must be repeated. 

It is interesting to note that the uptake patterns found for Mn2+ on the surface of calcite are similar to those observed for orthophosphate uptake on calcite. Stumm and Leckie (1970) observed a three-stage process for phosphate uptake on calcite surfaces from dilute solutions, representing adsorption, nucleation, and apatite growth. However, deKanel and Morse (1978) found a two-stage pattern of phosphate uptake on calcite from seawater, with an initial rapid adsorption phase followed by slow but steady uptake. 

Under our optimized sampling conditions, no blocking of the trap (visually verified at the manometer of the scavenging gas circuit) and no losses of volatiles during the adsorption phase (sensorially verified at the odor port) were observed. 

The type of clay mineral, depending on its abundance and degree of K+ (or NH4+) saturation, may control the adsorption, phase distribution and thus the mobility and (bio)availabihty of NACs in soils [152], The affinity of adsorption capacity of the clays for NACs increase in the order kaolinite < illite < montmorillonite [152],... 

In this section solids represent a partitioning or adsorption phase such as soil, asphalt pavement, or granular activated carbon. In contrast to air, water, and octanol, solid phases are typically very complex and poorly characterized. For example, many studies have shown that soils and sediments are characterized by many different types and amounts of organic matter and minerals, and that these different environments have various affinities for an organic chemical. The fugacity for the solid or sorbed phase is expressed as follows ... 

Contrary to thiophilic chromatography, HCIC does not require the presence of salts during the adsorption phase, thus immunoglobulin capture can be effected in physiological conditions and pH close to neutrality no feedstock pretreatment is required. Figure 17 shows no effect of ionic... 

Variations of these conditions can be made during adsorption phase to prevent capture of undesired impurities for instance, traces of albumin still present on the column and that can coelute with antibodies are washed out with diluted solutions of caprylic acid at neutral pH. Elutions can also be modulated by using different buffers at acidic pH such as acetate or citrate buffers. Higher the ionic strength of the buffer lower the pH for a complete elution of antibodies. 

In immunoaffinity chromatography adsorption phase is performed in physiological conditions followed by a wash with high ionic strength buffers to eliminate nonspecifically adsorbed proteins. Elution of human IgG is obtained by a deforming buffer such as a 0.2 M glycine-HCl, pH 2.7. 

In the Polybed version with ten adsorbent beds, three of them are in the adsorption phase at all times. Pressurization takes place in two steps, with an intermediate countercurrent purge by purified hydrogen, and a final cocurrem purge. Recompression also takes place in steps.The different sequences are programmed and automatically monitored. The yield in this case may reach 85 to 88 per cent for a feedstock containing 65 to 75 per cent volume hydrogen. 

SPE consists of analyte immobilization on the sorbent in the first stage, followed by selective elution of the components of interest by an appropriate solvent. Solid, adsorptive phases are selected according to their high affinity for the analytes (significantly higher than between analyte and donor phase). Proper eluent choice is the second factor influencing SPE efficiency. 

Figure 2 shows that the diffusion coefficients of ethyl alcohol evaluated according to Equation 2 are well in agreement with the experimental values, implying that transport through the adsorption phase is of no conspicuous consequence. Figure 2 also shows the diffusion... 

Therefore, minimal sample handling is advisable. In order to overcome the problem of limited sample loading, Guzman conceived and demonstrated the concept of on-line preconcentration with CE using a cartridge containing a bed of adsorptive phase (5). In the present work we describe the use of nonspecific on-line preconcentration-CE, on-line immunoaffinity-CE (lA-CE) and on-line microreactor enzyme digestion-CE for the analyses of proteins. 

The Dubinin-Radushkevitch equation (TOZM theory) was applied to calculate the micropores volume. Affinity coefficient for nitrogen was taken as 0.33, and adsorption phase densi at adsorption temp atures was taken as 0.808 g/cm [11], Micropores size was estimated from adsorption energy defined from the Dubinin-Radushkevitch equation using correlation X=10/E (run), where X is a semi-width of a slit micro-pore [12],... 

Another approach to increase the loadabihty is to enrich the analyte at the capillary inlet by means of an adsorptive phase, as reviewed in detail in Ref. 10. Re-versed-phase materials such as octadecyl-bonded silica have regularly been used in the form of membranes or column materials, thus, in principle, performing miniaturized SPE ( SPE) in-line with CE, allowing injections of 10-15 /uL. More selective sample concentration is obtained when using antibodies or Fab fragments for coating the inner wall of the capillary inlet [3,5]. 

In Figures 4 and 5 the individual adsorption isotherms x = /(x, ) are presented. For both mixtures the mole fractions of benzene in surface phase are higher for the carbon AC-2. It means that the adsorption phase is richer in preferentially adsorbed component, i.e. benzene. Thus, the selectivity of adsorption is higher in the case of carbon with narrower micropore system. 

Recent work reveals a much more complex adsorption phase diagram than was first suspected [28]. For the purposes of highlighting the creation of chirality from the adsorption of achiral molecules on achiral surfaces only the (9 0,1 1), (9 0,-1 1) and p(4x2) phases will be discussed [26]. 

IGC was also applied to generate adsorption data for organic vapor on polymeric materials. The vapor-adsorption phase equilibrium for various binary mixtures of organic compounds was further calculated on the basis of adsorption data for individual vapors. 

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