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Dionex Easion Operator's Manual
Channeling
The preferential flow of liquid along more open, less resistant paths through the
column packing. This causes Band Spreading.
Column Efficiency (N)
A measure of the narrowness of analyte bands as they elute from the column.
High efficiency is desirable because resolution between closely spaced bands
improves with greater efficiency. For a symmetrical (Gaussian) peak, column
efficiency can be determined by the following:
Where: t
= the peak retention time, in seconds
1
W
1/2
Column efficiency is proportional to column length: for a given resin and column
diameter, increasing the column length increases the column efficiency.
Synonymous with Theoretical Plates.
Column Selectivity (a)
Describes the relative separation of the band maxima between two adjacent peaks.
Selectivity can be determined by the following:
Where: t
and t
1
t
= retention time of unretained components (void volume)
0
Concentrator Column
A short column used to retain and concentrate analytes from a measured volume
of relatively clean sample. This allows large volumes of sample to be injected,
lowering concentration detection limits.
Conductivity
A measure of the ease with which electrical current flows through a liquid
contained between two oppositely charged electrodes. Conductivity is a
characteristic of ions in solution. Units are siemens.
Counterion
Ions carrying a charge opposite that of the sample ions (for example, Na
the counterion of a Cl
solution.
106
N = 5.54(t
/W
)
1
1/2
= the peak width at 1/2 height, in seconds
a = (t
- t
)/(t
-t
)
2
0
1
0
= retention time of components 1 and 2, respectively
2
-
analyte. These ions preserve electrical neutrality in
2
+
) may be
Doc. 155028-01 08/20
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