Page 65 - Illustrated Pocket Dictionary of Chromatography
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E
Eddy diffusion Also called axial diffusion, a band-broadening
effect caused by the flow stream splitting around particles in the
packed bed of a column. It is a component of the A term in the van
Deemter and Knox equations.
effective plates, N eff The calculation of the number of effective
plates generated by an analyte is determined by correcting for the non-
retained volume, t o:
N eff = 554 ( [ t r - ) w ] 2
.
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t o
where w 1/2 is the peak width at half-height and t r is the retention time
of the analyte. Essentially, N eff is N corrected for the system void
volume.
effective plate height, H eff H corrected for the void volume (as
are effective plates, N eff) and calculated as:
H eff = L N eff
where L is the column length.
efficiency Column (or more precisely system) efficiency is in-
versely proportional to the dispersion (broadening) of a peak that
elutes through it. The mathematical determination of efficiency is
accomplished through calculation of the number of theoretical plates
(N) or height equivalent to a theoretical plate (HETP).
effluent The entire mobile-phase stream that exits the column.
Ehrlich’s reagent [p-(dimethylamino)benzaldehyde, DMBA],
Ehrlich’s reagent is a derivatizing reagent used for the postcolumn
derivatization of primary amines and numerous sulfa drugs that
contain a primary amine (e.g., sulfadimidine, sulfanilamide, sulfadi-
azine). Detection is at 450nm.
Illustrated Pocket Dictionary of Chromatography, by Paul C. Sadek.
ISBN 0-471-20021-2 Copyright © 2004 John Wiley & Sons, Inc.
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