Chemistry Reference
In-Depth Information
Conditions:
Eluant 1:
50mM Mannitol, 2% CH
3
CN
35mM p-cyanophenol, 50mM NH3, 2% CH
3
CN
Eluant 2:
% CH
3
CN
Eluant 3:
20mL min
−1
Flow rate:
Columns:
ATC, AS6, AMMS
10mM H
2
SO
4
, 200mM H
3
BO
3
Regenerant
Range 30µS
Gradient program
Time
0
3
3.1
7
13
15
%1:
45
40
40
30
25
0
%2:
7
15
30
53
53
100
%3:
48
45
30
17
22
0
Source: Reproduced with permission from Dionex Corporation [24]
elution order of ions of different charge. In particular, increasing the gradient ramp slope
will cause sulphate and other divalent ions to elute earlier than nitrate. When the
considerations discussed in this technical note are followed, gradient elution can be used
to solve many chemical analysis problems that are difficult to solve using isocratic
elution.
Ion chromatograph:
Dionex series 400i or 1C with GPM
Trap column:
ATC (P/N 37151) or HPIC-AG8 (P/N37023)
Guard column:
HPIC-AG5A (P/N 37134)
Separator column:
HPIC-AS5A (P/N 3731)
Eluant 1:
0.75mM sodium hydroxide
Eluant 2:
200mM sodium hydroxide
1.0mL min
−1
Eluant flow rate:
Suppressor:
Anion MicroMembrane, AMMS (P/N 38019)
25mN H
2
SO
4
Regenerant:
10mL min
−1
Regenerant flow rate:
These workers made the following interesting observations.
Eluants used in anion exchange contain an anionic compound in high concentration
which competes with the analyte ions for sites on the resin. Gradient elution is best
accomplished by increasing the concentration of the eluant anion during the run, ie by
performing a concentration gradient. In addition, a pH gradient can be used, in which a
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