Exclusion limit upper

The main criterium for column selection is pore size distribution as it is desirable to have maximum pore volume for separation in the molecular weight range of interest. Having determined the upper molecular weight limit required, a column with a suitable exclusion limit should be selected. In the case of individual pore size columns, it is then a question of selecting other columns with complementary calibration curves to comprise a column set covering the re-... 

A minimal inert gas pressure of 0.6 torr is necessary to form powders exclusively. The upper limit of pressure is due to the reactor, which cannot be operated above 3.0 torr, at which pressure the plasma extinguished. 

In each case the upper figure represents the exclusion limit for the gel. 

The former plot shows the fractionation range of the gel, which is defined as the approximate range of within which a separation can be expected, provided that the molecules concerned are in different parts of the range. The upper end of the range Kj 0) is the exclusion limit, the Mr of the smallest molecule which cannot penetrate the pores of the matrix. The plot... 

In SEC, separation occurs due to differences in the accessibility of the intraparticular void volume by the sample components of different molecular dimensions. Molecules larger than the upper exclusion limit cannot enter the intraparticular void space and elute first, whereas sufficiently small molecules have access to all the pores, and therefore elute last, see Fig. 8. 

The elution of such gels is an example not of size exclusion but rather of hydrodynamic fractionation (HDF). However, it must be remembered that merely being able to physically fit an insoluble material through the column interstices is not the only criterion for whether the GPC/HDF analysis of an insoluble material will be successful. A well-designed HDF packing and eluant combination will often elute up to the estimated radius in Eq. (5), but adsorption can drastically limit this upper analysis radius. For example, work in our laboratory using an 8-mm-bead-diameter Polymer Laboratories aqueous GPC column for HDF found that that column could not elute 204 nM pSty particles, even though Eq. (5) estimates a critical radius of —1.5 jam. 

There are two main factors that influence the selectivity of a sensor limits in discrimination of an interfering ion and upper limits in stability constant of an analyte-ionophore complex. While an ideal ionophore does not form complexes with interfering ions, too strong complexation with the primary ion leads to a massive extraction of analyte into membrane phase coupled with a coextraction of sample counter-ions, known as Donnan exclusion failure. In such cases, at high activities and lipophilicities of sample electrolytes, fli(org) increases and a breakdown of membrane permselectivity prevents the Nemst equation to hold. 

The less basic purines generate different adducts. Both a C-8 adduct 107 and an 0-6 adduct 108 are produced in the presence of I, while the exclusive product of the reaction of A with 75n and 75o is the unique benzene imine 109. ° These purines also exhibit lower selectivity for trapping of the nitre-nium ions (Table 3). The pyrimidine nucleosides thymidine (T), uridine (U), and cytosine (C) showed negligible reactivity with these two nitrenium ions. ° The selectivity ratios for T, U, and C given in Table 3 are upper limits based on the decrease in the yield of the hydrolysis products at high nucleoside concentration (ca. 50mM). ° Since no adducts were isolated it is not clear that these selectivities represent nucleophilic trapping by the pyrimidines. 

It is noted that patent (2) favors the exclusion of asphaltenes by maximizing surface area contained by pore diameters of 30-70 A. Patent (3) discloses an upper limit on the amount of macropore volume represented by pore diameters greater than 100 A. Patents (4) and (5) suggest that catalysts containing mostly micropores will be poisoned soon asphaltenes penetrating the larger pores subsequently will block entrance to the smaller pores. 

Maximum allowable working pressure (MAWP) The maximum permissible gauge pressure of a vessel in its operating position at a designated temperature. The pressure is based on calculations for each element in a vessel, using nominal thickness exclusive of additional metal thickness allowed for corrosion. The MAWP is the basis for the upper limit of pressure setting of the safety relief devices that protect the vessel (see Section 3.6). 

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