Effect of column length

FIGURE 7.6 Effect of column length on the separation efficiency. Two different Fractogel EMD BioSEC columns (A 600 X 16 mm, B 1000 X 16 mm) were tested using BSA, ovalbumin, and cytochrome c (S/S/3 mg/ml) as sample (20 m/VI sodium dihydrogen phosphate, 300 m/VI NaCI, pH 7.2 0.5 ml/min). Better resolution can be achieved using longer columns. 

Koyama, J., Nomura, J., Shiojima, Y., Ohtsu, Y., and Horii, I., Effect of column length and elution mechanism on the separation of proteins by reversed-phase high-performance liquid chromatography, /. Chromatogr., 625, 217, 1992. 

Subsequent work by Petersen et al. also used TRU-Resin columns with a HPIC instrument however, the effects of column length were investigated and a 3-cm length was selected.61 Other parameters such as resin size and flow rate were examined, and eluent compositions were studied to minimize the use of oxalic acid. Decreased oxalic acid concentrations reduced the frequency of instrument cleaning. In the final scheme, the Np and Am were eluted in hydrochloric acid, followed by Pu and Th together as tetravalent species in a gradient that added oxalic acid. Last to elute was U. Coelution of Pu and Th was considered satisfactory because isobaric interferences between these elements was not a problem. 

Multicolumn analysis requires careful optimization. However, the effects of column length, phase ratio and particle size are all predictable, so that the separation that will be achieved on a multicolumn system can be predicted almost exactly. A different set of columns is usually required for every different analytical problem. 

HETP (Height equivalent to a theoretical plate). A measure of band spreading which compensates for the effect of column length. 

Figure 4-7. Effect of column length on the resolution obtained with DEAE cellulose exchange medium. (Copyright W. and R. Balston, Ltd., Maidstone, Kent, England.)...

Figure 12.15 Effect of column length on the separation of rare earths. The elution of mixtures of Sm203 (1st), Nd203 (2nd) and PrgOn (3rd) on -30+40 Amberlite IR-100. 22 mm ID column, 0.1% citrate solution, pH 5.30, linear flow rate 0.5 cm/min. Vertical broken lines indicate the boimdaries of the mixed zones between bands. Reproduced with permission from F.H. Spedding, E.I. Fulmer, J.E. Powell and T.A. Butler, J. Am. Chem. Soc., 72 (1954) 2354 (Fig. 8). 1954, American Chemical Society.

Table 10-1. The effect of column length on the first-order rate coefficient. ...

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 12. Effect of column length on enrichment in a total reflux enricher...

Figure 3.3. Chromatograms illustrating the effect of column length on efficiency, resolution, and sensitivity. Chromatograms courtesy of Agilent Technologies.

Figure 1.10 Effect of column length on the resolution. Chromatograms obtained with a GC instrument illustrating that by doubling the length of the capillary column, the resolution is multiplied by 1.41 or. ffl (adapted from a document of SGE Int. Ltd).

I Ian, N, J, Bhakta, and R.G. Carbonell. 1985. Longitudinal and lateral dispersion in packed beds effect of column length and particle size distribution. AIChE J, 31 277—288. 

Fig. 7. Simulated breakthrough of Cephalosporin C effect of column length (34).

Equation (7.70) does not allow for the possible effect of column length, and the effect of diameter may level off for sizes greater than 4 feet. For Z), = 4 ft and Uq = 100 ft/hr, Eq = 5900 ft /hr. With this value for Eq, the Peclet number for a reactor with L = 20 ft and a liquid velocity of 40 ft/hr would be Pe = = 0.14. For Peclet numbers much less than 1.0, the conversion for a first-order reaction is almost the same as for a perfectly mixed reactor, so the assumption of perfect mixing is usually justified for large bubble-column reactors. 

Figure 12.12 Effect of column length on elution time in programmed temperature GC of bacterial long-chain acid methyl esters. (Used with permission from Restek Corp.)...

FIGURE 4.4 The effect of column length on peak resolution. Nominal column lengths (a) 50-m, (b) 25-m, (c) 12-m, (d) 5-m, and (e) 2.5-m, 0.25-mm i.d., 0.25-p,m methylsili-cone. Conditions helium carrier gas, 100°C oven, split injection, FID detection. Peak identification (a) n-nonane, (b) 2-octanone, (c) n-decane, (d) 1-octanol, (e) 2,6-dimethylphenol, (f) n-undecane, (g) 2,4-dimethylanaline, (h) naphthalene, (i) n-dodecane. [Reprinted from LC/GC Magazine with permission of Advanstar Publications (5).]... 

Figure 5. Effect of column length and flow rate on preparative HPLC separation. Gradient test mixture chromatograms using linear gradient elution from 10% to 90% aqueous methanol containing 0.1% TEA. UV absorbance monitored at 220 nm. (a) 20 X 250 mm column, 10 mL min flow rate, 30 min gradient time, (b) 20 x 100 mm column, 20 mL min flow rate, 10 min gradient time, (c) 20 x 100 mm column, 40 mL min flow rate, 5 min gradient time, (d) 20 x 50 mm column, 20 mL min flow rate, 5 min gradient time.

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