Influence of Column Length

The following relationship exists between sensitivity and variation of the column length  

Example If a column of length 50 mm is used instead of one of length 250 mm, the sensitivity will increase as follows  

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Early Results About the Influence of Column Length on Resolution 58... 

Fig. 18a and b. Influence of column length. Gradient elution of a protein mixture on RP 8 columns of different length (a = 45x4.6 mm, b = 6.3x4.6 mm d0 = 30 nm). Gradient water/2-propanol, both with addition of 0.1 % TFA gradient rate 4%/ml flow rate 0.25 ml/min. The sample was a mixture of ribonuclease A, insulin, cytochrome C, bovine serum albumin, and ovalbumin (in the order of elution). These components were applied in the ratio 2 2 1.2 2 and totaled 50 pg. UV detection at 280 nm. (From Ref.73) with permission)... 

Fig. 29. Influence of column length on gradient elution of SAN copolymers through iso-octane/THF. Column packing material Polygosil 60-5 silica in both cases, do = 6 nm dP = 5 pm. Upper chromatogram column 55x4.6 mm, lower one column 150x4.6 mm. (The lower chromatogram is from the same run as the dashed line in Fig. 28.) Injection 60 pg in 30 pi THF [124]...

To determine the influence of column length upon the number of theoretical plates and upon resolution and to demonstrate the ability of increased resolution through utilization of recycle chromatography. 

Fig. 32.6 Influence of column length on analysis time. Analysis of phenols under isothermal conditions 1. phenol 2. o-cresol 3. 2,6-xylenol 4. p-cresol 5. n-cresol 6. o-ethylphenol 7. 2,4-xylenol 8. 2,5-xylenol 9. 2,3-xylenol 10. p-ethylphenol 11. m-ethylphenol 12. 3,5-xylenol 13. 3,4-xylenol.

Fig. 32.7 Influence of column length on analysis time. Analysis of bacterial acid methyl esters under temperature-programmed conditions.

Effects of Column Length. The influence of column length on the resolution and efficiency is known. To increase the resolution of a homologous substance pair by two, we must increase the column length by a factor of four. 

Figure 3.10 Influence of column length, (b) Synergi Fusion RP, 150x4.6mm, 4 im, (a) Syn-ergi Fusion RP, 20x4.6 mm, 2 jm.

The influence of column i.d. on the sensitivity is obviously greater than the influence of column length. Sensitivity will increase according to a square relationship with decreasing id. ... 

Nucleosil 100 Cl8 (3 pm) Influence of column I.D. and length, effect of applied counter pressure on linear velocity... 

Figure 8.13 Influence of column efficiency on the hodograph plot for a wide rectangular band. H - 0.02 cm column length (L, cm) and number of theoretical plates (N) 1, 1.0 (50) 2, 2.0 (100) 3,4.0 (200) 4, 8.0 (400). Reproduced with permission from Z. Ma and G. Guiochon,. Chromatogr., 603 (1992) 13 (Fig. 2).

Now that we are armed with a basic understanding of the hydrodynamics of chromatography, we can ask the question of the optimum column choice. We will first look at the interplay between column length and particle size, then we will examine the influence of column diameter. 

The steeper the gradient, the less the influence of the length of the column on the resolution... 

Retention time is also strongly influenced by the choice of stationary phase. Several factors must be taken into account when selecting a column for separating androgens. Retention time and resolution will be affected by the choice of column length, stationary film thickness and polarity, and the temperature program rate. The programmed temperature optimization of a mixture of anabolic... 

Highspeed SEC Columns The pore volume of the column packing has been shown to be one of the major factors influencing peak resolution in SEC. The reduction of the column length conld, in theory, reduce the time requirements of the separation substantially. However, several limitations predicted by chromatographic theory have to be considered. A study of the influence of column dimensions on fast SEC separations has been reported [9]. It has been... 

The allowable pressure drop influences the choice of the particle size and helps determine the column length. Equations for estimating the pressure drop in packed beds are given in Section 6. 

First, we must realize that many variables exist in any structural design. We can make a list of structural variables such as sizes, lengths of objects, materials, laminae orientations, and so on. those variables all have influence just as column length, moment of inertia, and Young s modulus influence column-buckling loads. The complete list of design variables will be called the vector Xj, and that vector will have N components. That list constitutes the definition of the structural configuration. 

The electrostatic effect of an ionic substituent on the reactivity of a functional group subject to attack by another ion persists over a much greater length of intervening chain than is found for the influence of an unionized substituent (compare column B of Table V). This follows of course from Coulomb s law. From the standpoint of polymer reactions, it is important to bear in mind that when charged... 

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