The width of a chromatographic peak is dependent on various dispersion processes operating both inside and outside the column. Extra column volume (ECV) is an important source of extra column dispersion (ECD) and can have significant detrimental effects, resulting in losses in column efficiency and therefore peak resolution. This Knowledge Note outlines how ECV and ECD can be easily measured.
When an analyte is injected onto an LC instrument, it migrates through the system and column in a discrete band. The measured width of the band is affected by dispersive processes occurring within the column packed bed (intra-column) and within the LC system components (extra-column). The total observed peak dispersion (σ2tot) defined as the variance of a Gaussian shaped peak, can be expressed as follows:
Where σ2col and σ2ext are the contributions from intra-column dispersion and extra-column dispersion (ECD) respectively.
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