Variances, extracolumn injection

There are four major sources of extracolumn dispersion (i) dispersion due to the injection volume, (ii) dispersion due to the volume of the detector cell, (iii) dispersion due to the detector response time, and (iv) dispersion resulting from the volume in the connecting tubing between the injector and the column and also between the column and the detector. Thus, extracolumn dispersion takes place between the injector and the detector, only, and the system volume contributed by the solvent delivery system does not contribute to dispersion. The total permitted extracolumn dispersion (variance) is shared, albeit unequally, between those dispersion sources. A commonly accepted criterion for the instrumental contribution to zone broadening, suggested by Klinkenberg,17 is that it should not exceed 10% of the column variance. 

How is the efficiency influenced by the BGE Peak I broadening is the result of different processes in CZE I occurring during migration [in addition, extracolumn effects contribute to peak width (e.g., that stemming from the width and shape of the injection zone, or the -f. aperture of the detector cell)]. If the system behaves I linearly, the individual peak variances (the second mo-9 ments), o j, are additive according to a... 

To get a handle on the relative contributions of the different contributions to extracolumn band spreading, we need to make some estimates of the individual variances. Let us first estimate the contribution of the injection... 

The influence of large injection volumes can be treated like any other extracolumn band-spreading effects. The band spreading inside the column is independent of the band spreading outside the column. Thus we can simply add the variance of the injection volume to the variance of the band contributed by the column ... 

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