Peak area particle size effects

The APMS used for this separation had an average particle size of 4-10 pm Normal phase HPLC of ferrocene and acetylferrocene performed with non-porous 1-3 pm spheres prepared in basic solution showed only one broad peak with no separation of the target molecules. Similarly, 20 pm spheres prepared in acidic solution showed no resolution of the ferrocenes (Figure 1). This indicates that particle size has some effect on the quality of the HPLC separation, but surface area is the major factor provided that the molecules to be separated can access the interiors of the mesoporous particles, which is dependent upon the pore size. (Experiments performed on APMS using confocal scanning laser microscopy indicated that these particles are porous throughout their interiors). 

A reduction in particle size results in an increase in the surface area, which facilitates an increase in the dissolution rate and therefore, also, an increase in the rate of absorption. Drugs administered as suspension are generally rapidly absorbed because of the large available surface area of the dispersed solid. For solid dosage forms such as tablets and capsules, decreasing the particle size facilitates dissolution and thus absorption. Figure 6.8 shows the effect of particle size on absorption and resultant blood levels after oral administration of chloramphenicol in rabbits. Peak blood levels occurred much faster with the smaller... 

When measuring intensity, the integrated line intensity (peak area) and not the maximum intensity (peak height) must be measured. Variations in lattice strain and particle size can significantly influence the line shape, but their effect on the integrated intensity will generally be minimal. 

There are a number of conflicting studies concerning the effect of particle size and particle-size distribution of the sample on the peak areas and Al in values. Speil et al. (2) found that the peak areas under the kaolin dehydration peak varied from 725-2080 mm2 over the particle-size range of 0.05-0.1 to 5-20 ju. It was also found that the A7 in values varied from 580-625°C. However, Norton (89) found that the A7 io values remained essentially constant but that the temperature at which the dehydration reaction was completed varied from 610-670°c >ver a particle-size range of <0.1 to 20-44 p. Grimshawet al. (90) agreed with the latter study in that, with particle sizes down to 1 fi, the thermal characteristics of the kaolin samples were independent of particle size. This effect is illustrated in Table 5.5. 

The effect of crystallinity of the sample is rather difficult to evaluate because of the definition of the term degree of crystallinity Carthew (91) defined the latter, in the case of kaolin samples, as the perfection of crystal orientation and not the size of the crystal. Using five different samples of kaolin, he found that the area of the endothermic dehydration peak decreased with a decrease in sample crystallinity. The peaks appeared to be sharper as the degree of crystallinity of the sample increased. This effect of crystallinity was said to be similar to that of change in particle size, and could probably be explained in a similar manner. 

The electrochemical active surface area (ECSA) reflects the total catalyst surface that has the potential to participate in the fuel cell reaction. It is typically measured by the hydrogen adsorption/desorption peak area or the CO oxidative stripping peak area. A larger ECSA normally gives better fuel cell performance. The ratio of ECSA to the mass of the catalyst is an indication of how effectively the precious metal catalyst is used. The ratio of ECSA to the total geometrical surface area of the catalyst estimated by the particle size is an indication of how effectively the catalyst surface is used. The latter ratio can be used to gauge how well (high ratio) or bad (low ratio) a catalyst layer is made. 

The effect of varying AI2O3 nanoparticle amounts (median particle size 13 nm and BET specific surface area 100 m. g ) in PS-AI2O3 nanocomposites on flammability was studied by Cinausero using a cone calorimeter (Table 12.4) [38]. The PS-AI2O3 nanocomposites were prepared by mixing, in an appropriate ratio, molten PS pellets and AI2O3 in a Haake PolyLab 60 cm mixer rheometer at 200 °C and 50 rpm. It was shown that peak HRR... 

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