Flashcards
chromotographic theory
Cards in this deck (6)
- 1capacity factor (k or k')a measure of the time an analyte spends in the column
k=(Vr-Vo)/Vo or (tr-to)/to - 2selectivity (alpha)a measure of the spacing between two peaks
alpha=k(B)/k(A) - 3column efficiencyusually expressed in theoretical plates per meter
efficiency=n*100/L
n-number of theoretical plates
L-column length(cm) - 4Height Equivalent of a Theoretical Plate (HETP or H)H is the length of column required for a single partition step to occur
- 5Eddy diffusionMobile phase moves through column packed with stationary phase. Solute molecules take different random paths through stationary phase. Band broadening occurs as the different paths have different lengths.
- 6Longitudinal diffusionAnalyte concentration is less at the edges of the band than at centre. Analyte diffused out from the centre tot the edges causing band broadening. If mobile phase velocity is high, analyte spends less time on the column, which decreases the effects of longitudinal diffusion.
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- MDM2 Flashcards on chromotographic theory, created by Karo on 29/04/2013.
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- Karo
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