Interstitial volume static

In addition, the interstitial volume can also be divided into two parts, the interstitial volume that is actually moving (V (m)) nd that part of the interstitial volume around the points of contact of the particles that is static (Vi(s)). 

It is important to realize that all static phases will contribute to retention and, as a result, a number of different distribution coefficients will control the retention of the solute. Nevertheless, the situation can be simplified to some extent. The static interstitial volume (Vi(s)) and the pore volume fraction (Vp(i)) will contain mobile... 

F fraction of the static interstitial volume accessible to the solute... 

The interstitial volume of the column is also made up of two parts that fraction of the interstitial volume that is moving (V (m)), and that fraction that is close to the points of contact between the individual particles and away from the flow-stream that is essentially static (V (S))... 

Unfortunately, even this modified equation does not describe the true practical situation in LC, as it is complicated by the fact that all silica-based materials exhibit exclusion properties. The pore diameter of silica-based stationary phases can range from, perhaps, 2-3 Angstrom to as much as 1000-2000 Angstrom. Consequently, some, otherwise open pores, are accessible to the solute while others are not, depending on the size of the molecule. Therefore, only those pores that have a diameter equal to, or greater than, that of the solute molecules are accessible and only the stationary phase within those pores can effect retention. In addition, the static interstitial volume between the particles can also exhibit exclusion properties and some of the static interstitial volume may also be inaccessible to the larger solutes. As a consequence, equation (12) must be further modified to give,... 

Where, (K) is the distribution coefficient of the solute between the moving phase and the static portion of the interstitial volume,... 

It IS seen that the distribution of the various chromatographically Important volumes within an LC column is neither simple nor obvious, it is also seen that about 70% of the column volume is occupied by mobile phase but only about 50% of that mobile phase is actually moving. Furthermore about 18% of the mobile phase is interstitial but static and about 3i% of the mobile phase is contained within the pores and is also static. Just over 6% of the mobile phase in the pores has a different composition to that of the mobile phase proper and thus constitutes a second stationary phase The stationary phase constitutes about 12% of the column volume which is equivalent to about 17% of the mobile phase content of the column. 

Interstitial Static Phase volume, by difference Total Pore Volume. By Difference... 

Interstitial Moving Phase Volume. From the Retention of Silica Smoke 1.41 ml Interstitial Static Phase Volume. By Difference 0.50ml... 

Interstitial Static Phase volume, by difference Total Pore Volume. By Difference Pore Volume Containing Components of the Mobile Phase Having Composition differing from that of the Moving Phase, by difference... 

Hard spheres have static thermodynamic properties. For hard spheres, a volume fraction < = 1 is unattainable, because there are always interstitial void spaces... 

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