Resolving power chromatographic column

It is seen from equation (9) that the resolving power of the column, as defined by Giddings, will be directly proportional to the square root of the number of effective plates. As a consequence (R) can be used by the chromatographer to directly compare the resolving power of columns of any size, or type. However, the value of (R) will vary with the value of (k ) for the solute, and so comparisons between columns must be made using solutes that have the same (k ) value. 

As a secondary consideration, the chromatographer may also need to know the minimum value of the separation ratio (a) for a solute pair that can be resolved by a particular column. The minimum value of (a) has also been suggested [8] as an alternative parameter that can be used to compare the performance of different columns. There is, however, a disadvantage to this type of criteria, due to the fact that the value of (a) becomes less as the resolving power of the column becomes greater. Nevertheless, a knowledge of the minimum value of (cxa/b) can be important in practice, and it is of interest to determine how the minimum value of (aA/B) is related to the effective plate number. 

It is also of interest to the chromatographer to know the minimum (a) value of a pair of solutes that can be separated on a particular column. In fact, this has been suggested, (11), as a basis for comparing the resolving power of different columns. The disadvantage of this type of criteria is that the value of (a) becomes smaller the higher the resolving capacity of the column. Nevertheless, the minimum value of (a) is important in practice and it is of interest to see if it can be related to the effective plate number of the column. 

Online trace enrichment is another attractive route for increasing the resolving power of liquid chromatographic methods. An automated system by which nitroxynil in cattle muscle tissue could be loaded onto an anion-exchange precolumn and then eluted and chromatographed on a polymeric analytical column has been described (354). In practice, this is the online and higher performance ana-... 

Sephadex G-25 buffered at alkaline pH s has been found to possess excellent resolving power in some cases (144, 145, 146). A column liquid chromatographic method for determining TC in various dosage forms was automated. Each chromatogram consisted of a continuous flow separation of components followed by a spectral determination of the column eluate at a rate of 12 samples per hour (147). Gel chromatography has also been applied to the analysis of TC antibiotics using a Bio-Gel P-2 column with 0.1M acetic acid as an eluent (148). 

Prior to the chromatographic separation of amino acids on Dowex 50 columns, Carsten (C5) first desalts the urine sample on Amberlite IR 100 or Duolite C 3 and removes most of the nitrogenous bases on Amberlite IRA 400. This preliminary treatment allows for amino acid separations at ordinary temperatures using 2M and 4M HC1 on H+ columns for elution, instead of buffer mixtures a single column of 25 g of Dowex 50 is sufficient for all amino acids and 350-375 one-milliliter fractions are collected. The resolving power of this method does not seem to be as satisfactory as Moore and Stein s procedures, and it is not less time nor labor consuming. 

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