Interstitial volume measurement

Dead-end volume Is estimated from mercury poroslmetry by measuring the amount of mercury liberated from the packing when the applied pressure Is released. This measurement approximates the volume occupied by blind channels or pockets within the Interstitial and pore volumes. Assuming that the Interstitial volume of the bed consists totally of blind channels, then the minimum percentage of dead-end volume within the pores of the packing is 61 and 47%, respectively, for the 100 and lOOOA... 

Some of the characteristic column volumes outlined in the previous argument were determined by Alhedal et al (11) in the examination of a commercially available reverse phase column packing, Zorbax Cs. These authors examined the exclusion properties of the interstitial volume of the column by measuring the retention volume of a number of salts of different molecular volume.The substances used, in ascending order of ion volume, were as follows,... 

It is seen that the closest measured value to the moving portion of the interstitial volume is obtained from the retention volume of sodium... 

The distribution coefficient Kj (Equation 2) is defined as the volume fraction of pores, in a stationary phase, which is effectively permeated by a solute of a given size. V0 is the interstitial volume of the porous medium, measured by the elution volume of a high molar mass solute that is totally excluded from the matrix pores. Ve is the elution volume of the product of interest. Vs represents the total solvent volume within the pores, available for small solutes. 

Since Vs is difficult to measure, it is common to use an alternative distribution coefficient, called Kav (Equation 3). In this approach, Vs is replaced by the difference between the total column volume (Vt) and the interstitial volume (VD) of the column packed with the chromatographic matrix (Ladisch, 2001 Moraes and Rosa, 2005). 

The diffusion coefficients associated with translational motions when the radii of the diffusing radicals are not much larger than that of the solvent are expressed more accurately by D = kTI6nrr T (where r is the radius of the diffusing radical assuming a spherical shape and r (=yxr ) is the microviscosity. The value of /, the microfriction factor, can be calculated or taken equal to DsE/f exptb the ratio between the Stokes-Einstein diffusion coefficient (that considers van der Waals volumes, but not interstitial volumes) and the experimentally measured diffusion coefficient, Dexpti- As will be discussed later, these relationships appear to hold even in some polymer matrices. 

There are few data about pharmacological management of chronic CSA nephrotoxicity in the clinical setting. McCulloch et al studied the effects of nifedipine in CSA-induced interstitial fibrosis in renal transplantation. The authors compared three groups of patients (conventional CSA dose versus conventional CSA dose plus nifedipine versus low CSA dose plus azathioprine) measuring baseline cortical interstitial volume fraction after one, six and 12 months of therapy. After six and 12 months interstitial volume was lower in patients treated with CSA plus nifedipine as compared with... 

The density of the fuel samples was determined using the approach of the bulk density which corresponds to the overall volume occupied hy a given mass of powder, including the pore and interstitial volumes. A one-litre volume was filled up with a measured amount of sample without tamping. Bulk density was determined according to ASTM E873-82. 

After injection of the sample onto the column the compounds that do not interact with the stationary phase will be eluted at time in the void volume Vq. The void volume represents the sum of the interstitial volume between the particles of the stationary phase and the accessible volume within the particle pores. The retention time of the sample (t,) is the time from injection to the time of maximum concentration in the eluted peak. The retention volume is the volume of solvent required to elute the solute as measured from the... 

Note In order to determine the interstititial fraction, one needs to know the interstitial volume and the column volume. The interstitial volume can be measured readily using a marker that is excluded from the pores. For beds in a fixed-volume container, the column volume is known as well, but it is unknown for radially compressed beds. However, the volume occupied by the particles can be determined from the pore volume, which also is easily measurable if the particle porosity is known. The particle porosity, in turn, can be determined in a separate experiment using the same markers for the totally included volume and the interstitial volume in a column of a known column volume. Therefore, after the particle porosity has been determined, the column volume in a radially compressed column can be calculated as the sum of the interstitial volume, the p>ore volume and the skeleton volume of the particle.)... 

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