Oritron Dionex Ion Chromatography System ICS-2100 - Manual (Page 272)

ICS-2100 Ion Chromatography System
260
Doc. 065291-01 3/09
Cell Constant (k)
A factor determined experimentally by measuring the conductance (G) of a
standard solution of known equivalent conductivity (k).
The value of k depends upon the surface area of, and distance between, the
electrode faces in the conductivity detector cell.
Where: l = length
A = area of one electrode (the other electrode is equal to
the first)
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:
N = 5.54(t
1
/W
1/2
)
2
Where: t
1
= the peak retention time (in seconds)
W
1/2
= the peak width at 1/2 height (in seconds)
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:
a = (t
2
- t
0
)/(t
1
-t
0
)
Where: t
1
and t
2
= retention time of components 1 and 2, respectively
t
0
= retention time of unretained components (void volume)
Concentrator Column
A short column used to retain and concentrate analytes from a measured volume
k
κ G ⁄
=
k l A
⁄
=