Retention range

Typical values for ate 20-40, considerably smaller than can be obtained with other HPLC systems, and results prljuurily from the limited retention range characteristic of SEC. 

The stabilization pond is practical where land is plentiful and cheap. It has a large surface area and a shallow depth, usually not exceeding 2 m (6 ft). Stabilization ponds have a long retention, ranging from 11 to 110 days [38], depending on the land available as well as the design requirement. 

Figure 4), by which time dealumination is largely complete. There follows a steady rate of zeolite destruction which results in an additional 42% loss of crystalline zeolite (relative to fresh catalyst) over the next 80 days (see Figure 4, Fractions B-F). Fraction F, representing the end point of the USY catalyst distribution, retains only 38% of the crystallinity characteristic of fresh catalyst. Fractions A-D, representing the major portion of this equilibrium catalyst, exhibit relative crystallinity retentions ranging from 83 to 66%.

FIGURE 24-9 Number of theoretical plates required to attain a resolution of 1.0 as a function of partition ratio for values of relative retention ranging from 1.005 to 1.1 [Equation (24-35)]. (From Tang and Harris. )... 

The particle size distribution of the material and the clarity required will dictate the micron retention of the medium. Fabrics tend to have a nominal micron retention range as opposed to an absolute micron retention rating. When using precoat on a machine that leaves a residual heel of solids, a more open cloth can be used. 

BSP retention is usually increased in acute cholecystitis, but only occasionally is it increased in acute peritonitis and other acute abdominal conditions (B60, W21). The mechanism in these conditions is either partial biliary obstruction or alteration in hepatic blood flow. The effect of morphine in causing BSP retention by constriction of the sphincter of Oddi is relevant (see Section 7.12). Burnett (B60) found increased BSP retention ranging from 5 to 20% in 5 out of 6 patients with minor ailments given morphine, all of whom had shown normal BSP retention on the previous day. 

Pulmonary retention ranged from 32 to 42% at 5, 25 or 50 ppm. Blood concentration of TBA increased slowly dming exposure and remained high for several hours after exposme. Renal clearance of TBA was low, suggesting extensive blood protein binding or extensive tubular reabsorption. 

Pressure (density) is the next most important parameter Modifier type has a strong influence on selectivity but offers limited flexibility Modifier concentration is the least effective variable when the retention range is optimal. Used to minimize tailing of some polar compounds. Has a significant effect on retention and selectivity of compounds affected by the additive. Additives (e.g. trifluoroacetic acid or isopropylamine) are used at a concentration of 0.1-1% in methanol. Strong acids (bases) are used to improve the peak shape of weak acids (bases). Steric hindrance minimizes the effectiveness of tertiary and quaternary amines as additives. 

Amicon Diaflo ultrafiltration membrane offer a selection of macrosolute retentions ranging from 500 to 300,000 molecular weight as cahbrated with globular macrosolutes. These values correspond to pore sizes between about 1 and 15 nm. Each membrane is characterized by its nominal out-off, that is, its abihty to retain molecules larger than those of a given size. 

Although amino acids and peptides can also be electrochemically detected under the conditions being used [218], Hardy et al. [261] could not identify any interfering signals in the monosaccharide retention range when analyzing hydrolysates of bovine fetuin and fibrinogen. UV active components of these protein hydrolysates elute either in the column void volume or far behind the monosaccharides. 

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