Effect of sample concentration

Figure 4.19 demonstrates the effect of sample concentration on the separation of polyethylene oxide (PEO). At a concentration of 1.6 mg/ml of each... 

Figure 4, Effect of sample concentration on the distribution of milk proteins on Spherogel TSKSW 2000 column. Instant, nonfat, dry milk was dissolved in mobile phase at the indicated concentrations and 10-fjJL aliquots injected under the conditions outlined in Figure 1.

The understanding of the effects of sample concentration (sample mass) in field-flow fractionation (FFF) has being obtained gradually with the improvement of the sensitivity (detection limit) of high-performance liquid chromatography (HPLC) detectors. Overloading, which was used in earlier publications, emphasizes that there is an upper limit of sample amount (or concentration) below which sample retention will not be dependent on sample mass injected into the FFF channels [1]. Recent studies show that such limits may not exist for thermal FFF (may be true for all the FFF techniques in polymer separation), although some of the most sensitive detectors on the market were used [2]. 

Fig. 1 Fractograms of PMMA in THF showing the effect of sample concentration on retention. Experimental conditions cold-wall temperature, 25°C, T, 50°C flow rate, 0.1 mL/min.

Fig. 13.6 Effect of sample concentration on the % recovery of polymer from model polyolefins using xylene/n-hexane at 140 °C...

The effect of sample concentration on the chromatographic behaviour of ionic solutes on Sephadex G-10 can be qualitatively described by means of the partition isotherms derived on the basis of the ion partition model proposed by Shibukawa et al. [ref. 69] (see Sec. 2.2.1). The overall partition isotherms are anticipated to be represented as shown in Fig. 9 from the analogy with typical ion-exchange isotherms [ref. 70], if the partition isotherm of process (A) is linear. It is thus predicted that, in the system where the contribution of the steric exclusion effect can be neglected, the difference in the affinity for the internal gel phase between sample ion, s , and coion Y , that is, the equilibrium constant of ion-exahange process (B), K, determines the sample concentration dependence of the elution behaviour of sample ion in the following manner. When > 1, the elution volume or the distribution coefficient of sample ion decreases and the elution profile is more skewed with sharp leading... 

The effect of sample concentration on the elution of sample ion is expected to be independent of the type of the counterion, x , in the eluent, provided... 

Fig. 10. Effect of sample concentration on the chromatograms of nitrate ions. Column Sephadex G-10, 8 x 700 mm temperature 25.0 0.1 C flow rate 0.70 cm /min. Eluent a, NaC10 b, Nal c, NaNOs d, NaCl e, HCOONa. Sample concentration ------, 0.01 M ------, 1 M.

The relative effectiveness of nucleating agents in a polymer can be determined by measuring recrystallization exotherms of samples molded at different temperatures (105). The effect of catalyst concentration and filler content has been determined on unsaturated polyesters by using dynamic thermal techniques (124). Effects of formulation change on the heat of mbber vulcanization can be determined by dsc pressurized cells may be needed to reduce volatilization during the cure process (125). 

The reactive extrusion of polypropylene-natural rubber blends in the presence of a peroxide (1,3-bis(/-butyl per-oxy benzene) and a coagent (trimethylol propane triacrylate) was reported by Yoon et al. [64]. The effect of the concentration of the peroxide and the coagent was evaiuated in terms of thermal, morphological, melt, and mechanical properties. The low shear viscosity of the blends increased with the increase in peroxide content initially, and beyond 0.02 phr the viscosity decreased with peroxide content (Fig. 9). The melt viscosity increased with coagent concentration at a fixed peroxide content. The morphology of the samples indicated a decrease in domain size of the dispersed NR phase with a lower content of the peroxide, while at a higher content the domain size increases. The reduction in domain size... 

Extensive studies on the effect of substrate concentration and on the bioavailability of the substrate to the appropriate microorganisms have employed samples of natural lake water supplemented with suitable nutrients. There are few additional details that need to be added since the experimental methods are straightforward and present no particular difficulties. Considerable use has also been made of a comparable methodology to determine the fate of agrochemicals in the terrestrial environment. 

Table V shows the concentrations of polymer (usually in THF/polymer/monomer mixtures), the GPC that they were directly injected into, and the Column Code involved (Ref. Table 1). No effect of different concentration was observed in the chromatograms from GPC 2 when concentrations of samples A to E inclusive were changed by 33%. GPC 1 chromatograms were too disturbed by sampling to be useful except as a rough guide to sampling position.

In preformulation one task is to establish the stability of the drug substance in both solid and dissolved state. In the latter case it is important, with small samples of drug substance, to assess (a) the effect of buffer type, (b) the effect of buffer concentration, (c) the effect of pH in a practical range, (d) the effect of temperature, and (e) the kinetic salt effect. 

The Effect of Catalyst Concentration The first parameter that was studied was the effect of the catalyst concentration. Samples impregnated with 1, 5, 10 and 15% tin as stannous chloride and a sample with no catalyst were hydrogenated at 450°C to investigate the effect that increasing catalyst concentration has on the composition of the oil (hexane soluble portion) formed. 

On well characterised non-stabilized PP samples [48] having molar mass within 45-180 kg/mol with differing tacticity and crystallinity, we can see that the increasing molar mass leads to an increase of induction time and reduction of the maximum chemiluminescence intensity (Figure 14). The polymer with higher average molar mass appears to be more stable than that with lower molar mass. This may be ascribed to the effect of increased concentration of more reactive terminal groups, which promote initiation of thermal oxidation. 

Schmitt, C.J. and S.E. Finger. 1987. The effects of sample preparation on measured concentrations of eight elements in edible tissues of fish from streams contaminated by lead mining. Arch. Environ. Contam. Toxicol. 16 185-207. 

Sablani, S.S. and Rahman Shafiur, M. 2003. Effect of syrup concentration, temperature and sample geometry on equilibrium distribution coefficients during osmotic dehydration of mango. Food Res. Int. 36, 65-71. 

Table 9.11 shows the effect of this concentration on the responses of the other pesticides. In every instance the peak height was increased while the peak area remained constant. All of the columns used for this study were aged by repeated sample injections, but had not deteriorated to the point where they would normally be replaced. No values are included in Table 9.11 where the chromatographic system was not suitable for the pesticide concerned. 

After final chromatographic purification, samples of the AT-systems were cured in air at 288°C (550°F) for eight hours. Samples chosen for curing included pure monomers, monomer/oligomer mixtures produced by the stoichiometry outlined In the previous section, and In one case (the bisphenol-A based resin) pure oligomer. This set of samples was selected to provide data showing the effect of oligomer concentration on thermomechanical properties. 

Few reports are available on the potential effect of chemical concentration on the BAF in an aquatic organism (e.g., Mayer, 1976). Yet, a key assumption of EP theory is the independency of BAF relative to exposure concentration. To our knowledge, there is only one report (Huckins et al., 2004) in the peer-reviewed literature, where the effect of chemical exposure level on concentration factors (CFs) or BAFs has been tested in side-by-side BMO and passive sampler exposures. Huckins et al. (2004) defined CF as the ratio of the concentration in a sample matrix (whole body [soft tissues in the case of bivalves] or whole SPMDs) relative to the concentration in the ambient exposure medium at any moment in time, whereas the A sw and BAF (includes biomagnilication) represent the maximal CF. Similar to ATs s and BAFs, CFs are expected to be independent of exposure concentrations, when residue exchange follows first-order kinetics. 

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